Class 10 Chemistry - Chemical Reactions And Equations

Complete the statement by filling the gaps using the appropriate terms.
An ...... is drawn in between the reactants and products while writing the equation for a chemical reaction.

An arrow is drawn in between the reactants and products while writing the equation for a chemical reaction.

Give the reason for the following:
Respiration is an exothermic reaction.

During respiration, glucose combines with the oxygen in the cells of the body and releases energy. Hence respiration is an exothermic reaction.

Reaction can be written as,

$$C_6H_{12}O_{{6}{(aq)}} + O_{{2}{(aq)}} \longrightarrow 6CO_{{2}{(aq)}} + 6H_2O_{(liq)} + energy $$

Mention the types of chemical reactions.

The chemical reactions are mainly of the following types based on the nature of reactants and products.

1. Combination reaction

2. Decomposition reaction

3. Displacement reaction

4. Double displacement reaction

A decomposition reaction taking place due to the passage of electric current is called ___________.

A decomposition reaction taking place due to the passage of electric current is called electrolysis.

In electrolysis, an electric current is passed through an ionic substance that is either in a molten state or dissolved in a suitable solvent to bring about the chemical reactions at the electrodes. So the correct answer is electrolysis.

The arrow mark between the products and reactants of a chemical equation shows __________ of the reaction.

The arrow mark between the products and reactants of a chemical equation shows the direction of the reaction.

$$CuSO_4+Zn\longrightarrow ZnSO_4+Cu$$

In the reaction, copper sulphate reacts with zinc to form zinc sulphate and copper. Here, the arrow sign shows the direction of the reaction.

What is a combination reaction? Write combination reaction of quick lime with water.

A combination reaction is a reaction where two or more elements or compounds (reactants) combine to form a single compound (product).

The combination reaction of quick lime with water is as follows:

$$\underset{quick\ lime}{Ca{ O }}\quad +\quad { H }_{ 2 }O\quad \longrightarrow \quad \underset{calcium\ hydroxide}{Ca{ (OH) }_{ 2 }}\quad +\quad \triangle_{Heat} $$

Write balanced chemical equations for the following word equation:
Nitrogen + Oxygen $$\rightarrow $$ Nitric Oxide

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Write a balanced chemical equation for each of the following:
Action of dilute hydrochloric acid on Iron

$$\bullet$$ When dilute hydrochloric acid is added to iron, then iron (II) chloride $$(FeCl_2)$$ and hydrogen gas are produced.

$$\bullet$$ The balanced chemical equation for the reaction is as follows:

$$Fe+2HCl\rightarrow FeCl_{2}+H_{2}$$

$$\bullet$$ In the reaction, Iron displaces hydrogen from HCl acid to form iron (II) chloride. Thus, it is a single displacement reaction.

Name the substance oxidized and reduced in the given reaction
$$Cl_2 + H_2S\rightarrow 2HCl + S$$

In this reaction, Chlorine $$(Cl)$$ gets reduced by gaining hydrogen to form $$HCl$$.

$$(Cl_2\rightarrow HCl)$$

$$H_2S$$ is oxidized to form $$S$$ by losing hydrogen.

$$(H_2S\rightarrow S)$$

$$\bullet$$ The substance that gains hydrogen is said to be reduced substance(reduction)

$$\bullet$$ The substance that loses hydrogen is said to be an oxidized substance(oxidation).

Write a balanced chemical equation for each of the following:
Action of heat on calcium bicarbonate

$$\bullet$$ When calcium bicarbonate $$(Ca(HCO_3)_2)$$ is heated, it decomposes and produces calcium carbonate $$(CaCO_3)$$, water and carbon dioxide.

$$\bullet$$ The balanced chemical equation for the reaction is given below.

$$Ca\left(HCO_{3}\right)_{2}\overset{\Delta }{\rightarrow}CaCO_{3}+CO_{2}+H_{2}O$$

$$\bullet$$ Carbon dioxide is the gas that turns lime water milky.

Write equations for the following reactions:
(i) Aluminium oxide and Sodium hydroxide.
(ii) Zinc and dilute sulphuric acid.

(i) The chemical equation for the reaction when aluminium oxide $$(Al_2O_3)$$ reacts with sodium hydroxide $$(NaOH)$$ to form sodium aluminium oxide $$(NaAlO_2)$$ and water $$(H_2O)$$ is as follows:

$$Al_2O_3 + 2NaOH\rightarrow 2NaAlO_2 + H_2O$$

$$\bullet$$ This reaction is an acid-base reaction (neutralization reaction) in which acid $$(Al_2O_3)$$ reacts with base $$(NaOH)$$ to produce salt $$(NaAlO_2)$$ and water $$(H_2O)$$.

$$\text{Additional information}$$

$$\bullet$$ Aluminium oxide $$(Al_2O_3)$$ is an amphoteric oxide.

$$\bullet$$ Amphoteric oxides are oxides that react with both acids and bases to produce salts and water.

$$\bullet$$ For example, aluminium oxide reacts with hydrochloric acid to form aluminium chloride and water.

$$Al_2O_3 + 6HCl\rightarrow 2AlCl_3 + 3H_2O$$ and

Aluminium oxide reacts with sodium hydroxide (base) to form sodium aluminate and water.

$$Al_2O_3 + 2NaOH\rightarrow 2NaAlO_2 + H_2O$$

(ii)The chemical equation for the reaction when zinc $$(Zn)$$ reacts with sulphuric acid $$(H_2SO_4)$$ to form zinc sulphate $$(ZnSO_4)$$ and hydrogen gas $$(H_2)$$ is as follows:

$$Zn+ H_2SO_4\rightarrow ZnSO_4 + H_2$$

$$\bullet$$ This reaction is a displacement reaction in which zinc, being more reactive than hydrogen, displaces the hydrogen from sulphuric acid to form zinc sulphate.

A student took a solution of copper sulphate in a beaker and put a clean iron nail into it and left it for about an hour.
a) What changes do you expect?
b) Are these changes chemical in nature?
c) Write a word equation for the chemical change, if any.

a) From the given statement, expected changes are given below:
i) Colour turns from blue to green.
ii) A brown colour is found to be deposited on iron nail surface.

b) Yes, the nature of these changes are chemical. The reason behind this is 'iron sulphate' and copper are produced in the reaction.

c) The reaction is:
$$Copper$$ $$sulphate (Blue)+Iron (Shining$$ $$white)\rightarrow Iron$$ $$sulphate (Green)+Copper (Brown)$$.

Write the essential condition for the following reaction to take place:
$$2AgBr\rightarrow 2Ag + Br_2$$
Write an application of this reaction.

$$\textbf{Part 1: Essential Conditions}$$

$$\cdot$$ The essential condition for the reaction to take place is sunlight.

$$\cdot$$ Silver bromide undergoes decomposition reaction in the presence of sunlight to form silver metal and bromide.

$$2AgBr\rightarrow 2Ag + Br_2$$

$$\cdot$$ This reaction is a photochemical reaction.

$$\textbf{Part 2: Application}$$

This reaction is used in white and black photography.

An iron salt A reacts with NaOH to form a green precipitate. Another iron salt B reacts with NaOH to form a brown precipitate. Identify the iron salts, A and B along with their colours and write the reactions involved.

$$\textbf{Part 1: Identify the salt A}$$

Ferrous sulphate (iron salt) reacts with NaOH and produces a green precipitate of ferrous hydroxide. The chemical equation for the reaction is as follows:

$$FeSO_{4}+2NaOH\rightarrow Fe\left(OH\right)_{2}(s)+Na_{2}SO_{4}$$

Therefore, the iron salt A is $$FeSO_{4}$$

$$\textbf{Part 2: Identify the salt B}$$

Ferric sulphate (iron salt) reacts with NaOH and produces a brown precipitate of ferric hydroxide. The chemical equation for the reaction is as follows:

$$Fe_{2}\left(SO_{4}\right)_{3}+6NaOH\rightarrow 2Fe\left(OH\right)_{3}(s)+3Na_{2}SO_{4}$$

Therefore, the iron salt B is $$Fe_{2}\left(SO_{4}\right)_{3}$$

Activity:
Take lead nitrate solution in a test tube.
Add potassium iodide solution to this.
What do you observe ?

This leads to the formation of a yellow precipitate of lead iodide.

$$\text{Explanation}:$$

$$\bullet$$ When lead nitrate is reacted with potassium iodide, it produces lead iodide and potassium nitrate.

$$\bullet$$ The reaction between the two is known as double displacement and precipitation reaction.
$$\bullet$$ A yellow precipitate of lead iodide is formed in the reaction.

$$\bullet$$ The chemical equation following the above reaction is:

$$Pb(NO_3)_2(aq.) + 2KI(aq.) \rightarrow PbI_{2}(s) + 2KNO_{3}(aq.)$$

By Stoichiometry of the reaction:
$$\bullet$$ 1 mole of lead nitrate reacts with 2 moles of potassium iodide to produce 1 mole of lead iodide and 2 moles of potassium nitrate.

What is a redox reaction? Identify the substances oxidized and the substances reduced in the following reactions.

1) $$2PbO + C\rightarrow 2Pb+CO_2$$
2) $$MnO_2 + 4HCl\rightarrow MnCl_2 + 2H_2O + Cl_2$$

$$\bullet$$ Redox reactions are those reactions in which both oxidation and reduction take place simultaneously.

1) $$2PbO + C \rightarrow 2Pb+CO_2$$

In this reaction, $$PbO$$ undergoes reduction by losing oxygen to form $$Pb$$

$$PbO\rightarrow Pb$$

$$C$$ undergoes oxidation, because it is gaining oxygen, forming $$CO_2$$

$$C\rightarrow CO_2$$

2) $$MnO_2 + 4HCl \rightarrow MnCl_2 + 2H_2O + Cl_2$$

In this reaction, $$MnO_2$$ undergoes a reduction reaction by losing oxygen to form $$MnCl_2$$.

$$MnO_2\rightarrow MnCl_2$$

$$Cl$$ undergoes oxidation by losing hydrogen to form $$Cl_2$$

$$HCl\rightarrow Cl_2$$

$$\textbf{Additional information}$$:

$$\bullet\text {The substance which gains oxygen or loses hydrogen is called an oxidised substance and such reactions are called oxidation reaction}$$.

$$\bullet\text{The substance which loses oxygen or gains hydrogen is called a reduced substance and such reactions are called reduction reaction}$$.

A student has mixed the solutions of lead $$ (II) $$ nitrate and potassium iodide.
(i) What was the colour of the precipitate formed? Can you name the compound?
(ii) Write the balanced chemical equation for this reaction.
(iii) What type of reaction is it?

(i) The colour of the precipitate formed is yellow and the name of precipitated is $$Lead\ iodide\ (PbI_2)$$.

(ii) The balanced chemical equation for this reaction is as follows:

$$2Pb(NO_3)_2 + 4KI\rightarrow 2PbI_2 + 4KNO_3$$

Lead Nitrate: $$Pb(NO_3)_2 $$

Potassium Iodide: $$KI$$

Potassium Nitrate: $$KNO_3$$

Lead Iodide:$$PbI_2$$

(iii) The type of reaction involve in this chemical reaction is double displacement reaction, as, both of the ions are being exchange.

Classify each of the following reactions as a combination, decomposition, displacement, or double displacement:
$$CaO+H_{2}O\rightarrow Ca\left(OH\right)_{2}$$

The given reaction is as follows:

$$CaO+H_{2}O\rightarrow Ca\left(OH\right)_{2}$$

In the reaction, CaO combines with water to form calcium hydroxide as a product. Thus, it is a combination reaction.

$$\text{Name the organic compound prepared by each of the following reactions}:$$
$$CH_{3}COONa + NaOH \xrightarrow[\Delta]{CaO}$$

$$CH_{3}COONa + NaOH \xrightarrow[\Delta]{CaO} Na_2CO_3 + CH_4$$

$$\bullet$$ When sodium acetate ($$CH_3COONa$$) and sodium hydroxide ($$NaOH$$) are melted together, methane ($$CH_4$$) is released, and the released carbon dioxide interacts with sodium hydroxide, and forms sodium carbonate ($$Na_2CO_3$$).

$$\bullet$$ This reaction is called 'Dumas reaction'.

When ammonium chloride is dissolved in water in a test tube, the test tube becomes cold why?

$$\bullet$$ When ammonium chloride $$(NH_4Cl)$$ is dissolved in water, the test tube becomes cold because it is an endothermic reaction.

$$\bullet$$ In an endothermic reaction, the heat is absorbed from the surrounding which is a form of energy.

Classify each of the following reactions as a combination, decomposition, displacement, or double displacement:
$$BaCl_{2}+Na_{2}SO_{4}\rightarrow BaSO_{4}+2NaCl$$

The given reaction is as follows:

$$BaCl_{2}+Na_{2}SO_{4}\rightarrow BaSO_{4}+2NaCl$$

In the reaction, exchange of ions in both the reactants takes place to form two new products that are $$BaSO_{4}$$ and NaCl. Thus, it is a double displacement reaction.

2 g of ferrous sulphate crystals are heated in a dry boiling tube. Name the type of chemical reaction taking place.

$$FeSO_4.7H_2O \overset{heat}{\rightarrow} FeSO_4$$

$$FeSO_4 \overset{heat}{\rightarrow} Fe_2O_3 + SO_2(g) + SO_3(g)$$

$$\bullet$$ In this reaction, it is observed that single reactant break down to give different products. This is a decomposition reaction.

Classify each of the following reactions as a combination, decomposition, displacement, or double displacement:
$$2KClO_{3}\rightarrow 2KCl+3O_{2}$$

$$\bullet$$ The reaction in which one reactant decomposes into two or more products is known as 'decomposition reaction'.

$$\bullet$$ The given reaction is as follows:

$$2KClO_{3}\rightarrow 2KCl+3O_{2}$$

$$\bullet$$ Here, Potassium chlorate decomposes into potassium chloride and oxygen. Thus, it is a decomposition reaction.

Name the gas that evolved when ethanoic acid is added to sodium carbonate. How would you prove the presence of this gas?

Reaction: When ethanoic acid is added to sodium carbonate.

$$2CH_3COOH(aq)+Na_2CO_3(aq)\to 2CH_3COONa(aq)+H_2O(l)+CO_2(g)$$

Carbon dioxide $$(CO_{2})$$ gas is evolved in the reaction. When passed through lime water, it turns lime water milky.

2 g of ferrous sulphate crystals are heated in a dry boiling tube.Is this also a double displacement reaction ?

$$FeSO_4.7H_2O \overset{heat}{\rightarrow} FeSO_4$$

$$FeSO_4 \overset{heat}{\rightarrow} Fe_2O_3 + SO_2(g) + SO_3(g)$$

$$\bullet$$ Double displacement reactions may be defined as the chemical reactions in which one component each of both the reacting molecules is exchanged to form the products.

$$\bullet$$ During this reaction, the cations and anions of two different compounds switch places, forming two entirely different compounds.

$$\bullet$$ Therefore, this is not a double displacement reaction.

Why can copper displace silver from silver nitrate and silver cannot displace copper from copper sulphate solution? Give example.

In a displacement reaction, a more reactive element displaces a less reactive element from its compounds.

$$\bullet$$ Copper displaces silver from silver nitrate because copper is a more reactive element/metal as compared to silver. But silver cannot displace copper from its copper sulphate solution because it is less reactive than copper.

$$\bullet$$ The chemical equation for the displacement reaction in which copper displaces silver from its compound is given as,

$$Cu(s)+2AgNO_3(aq)\rightarrow Cu(NO_3)_2(aq)+Ag(s)$$

Identify the following reactions as
i) combination ii) decomposition iii) displacement reactions and double
displacement reaction
$$CaCO_{3}(s) \rightarrow CaO(s) + CO_{2}(g)$$

$$\text{Correct Answer: Decomposition reaction}$$

The given reaction is as follows:

$$CaCO_3(s)\rightarrow CaO(s)+CO_2(g)$$

$$\bullet$$ Since in the given reaction, calcium carbonate $$(CaCO_3)$$ decomposes to produce two new compounds $$(CaO)$$ and $$(CO_2)$$ thus, it is a $$\textbf{decomposition reaction}$$.

$$\textbf{Additional Information}$$

$$\bullet$$ A chemical reaction in which one reactant breaks down into two or more products is known as a decomposition reaction.

Identify the following reactions as
i) combination ii) decomposition iii) displacement reactions and double
displacement reaction
$$ Fe_{2}O_{3} + Al \rightarrow Al_{2}O_{3} + 2Fe $$

$$\text{Correct Answer: Displacement reaction}$$

The given reaction is as follows:

$$Fe_2O_3+2Al\rightarrow Al_2O_3+2Fe$$

In the reaction, because Al being a more reactive metal displaces Fe (a less reactive metal) from its compound and produces $$Al_2O_3$$ and $$Fe$$ thus, it is a $$\textbf{displacement reaction}$$.

$$\textbf{Additional Information:}$$

A chemical reaction in which a more reactive element displaces a less reactive element from its compound is known as displacement reaction.

Identify the following reactions as
i) combination ii) decomposition iii) displacement reactions and double displacement reaction
$$Pb(s) + CuCl_{2} \rightarrow PbCl_{2} + Cu(s)$$

$$\text{Correct Answer: Displacement reaction}$$

The given reaction is as follows:

$$Pb(s)+CuCl_2\rightarrow PbCl_2+Cu(s)$$

In the reaction, lead (Pb) being a more reactive metal displaces Cu (a less reactive metal) from its compound and forms the products $$PbCl_2$$ and $$Cu$$ thus, it is a $$\textbf{displacement reaction}$$.

$$\textbf{Additional Information:}$$

A chemical reaction in which a more reactive element displaces a less reactive element from its compound is known as a displacement reaction.

Identify the following reactions as
i) combination ii) decomposition iii) displacement reactions and double displacement reaction
$$NaCl + AgNO_{3} \rightarrow AgCl + NaNO_{3} $$

$$\text{Correct Answer: Double displacement reaction}$$

The given reaction is as follows:

$$NaCl+AgNO_3\rightarrow AgCl+NaNO_3$$

In the reaction, two compounds $$NaCl$$ and $$AgNO_3$$ react by an exchange of ions to form the products $$AgCl$$ and $$NaNO_3$$ thus, it is a double displacement reaction.

$$\textbf{Additional Information}$$

A chemical reaction in which two reactants react by an exchange of ions to form two new compounds is known as a double displacement reaction.

Name the brown coloured gas evolved when lead nitrate crystal are heated in dry test-tube.

$$\bullet$$ When lead nitrate crystals $$[Pb(NO_3)_2]$$ are heated in a dry test tube, the evolution of brown coloured nitrogen dioxide gas takes place.

$$\bullet$$ The balanced chemical equation for the reaction is as follows:

$$2Pb(NO_3)_2\rightarrow 2PbO+4NO_2 \uparrow + O_2\uparrow$$

$$Zn + H_{2}SO_{4} \rightarrow ZnSO_{4} + H_{2}$$
Write the ionic equation for the reaction.

The given reaction is:

$$Zn + H_{2}SO_{4} \rightarrow ZnSO_{4} + H_{2}$$

The ionic reaction is as follows:

$$Zn(s) + 2H^{+}(aq) + SO_4^{2-} \rightarrow H_2(g) + Zn^{2+}(aq) + SO_4^{2-}$$

Identify the following reaction as
i) combination ii) decomposition iii) displacement reactions and double displacement reaction.
$$ZnCO_{3}(s) \rightarrow ZnO(s) + CO_{2}(g)$$

$$\text{Correct Answer: Decomposition reaction}$$

The given reaction is as follows:

$$ZnCO_3(s)\rightarrow ZnO(s)+CO_2(g)$$

$$\bullet$$ Since in the given reaction, zinc carbonate $$(ZnCO_3)$$ decomposes and produces two new compounds $$(ZnO)$$ and $$(CO_2)$$ thus, it is a $$\textbf{decomposition reaction}$$.

$$\textbf{Additional Information:}$$

A chemical reaction in which one reactant breaks down into two or more products is known as a decomposition reaction.

Identify the following reactions as
i) combination ii) decomposition iii) displacement reactions and double
displacement reaction
$$3H_{2}(g)+ N_{2}(s) \rightarrow 2NH_{3} $$

$$\text{Correct Answer: Combination reaction}$$

The given reaction is as follows:

$$3H_2(g)+N_2(g)\rightarrow 2NH_3(g)$$

In the reaction, hydrogen $$(H_2)$$ combines with nitrogen $$(N_2)$$ to form ammonia $$(NH_3)$$. Thus, it is a $$\textbf{combination reaction}$$.

$$\textbf{Additional Information:}$$

A chemical reaction in which two or more reactants combine to form a single product is known as combination reaction.

Identify the following reactions as
i) combination ii) decomposition iii) displacement reactions and double displacement reaction
$$H_{2}(g)+ Cl_{2} \rightarrow 2HCl$$

$$\text{Correct Answer: Combination reaction}$$

The given reaction is as follows:

$$H_2+Cl_2\rightarrow 2HCl$$

In the reaction, hydrogen $$(H_2)$$ combines with chlorine $$(Cl_2)$$ to form hydrogen chloride $$(HCl)$$. Thus, it is a $$\textbf{combination reaction}$$.

$$\textbf{Additional Information:}$$

A chemical reaction in which two or more reactants combine to form a single product is known as combination reaction.

Following observations are recorded during a number of experiments on the substance P. When the substance P is heated, a reddish brown gas is evolved along with a gas which relights glowing wooden splint. A yellow residue is left in the test tube.
Name the gas which relights the glowing splint.

Reaction involved in this experiments is:-

$$Pb(NO_3)_2 \overset{\Delta }{\rightarrow} PbO \downarrow + 2NO_2(g) + O_2(g)$$

$$\bullet$$ Lead nitrate ($$Pb(NO_3)_2$$), when heated strongly in a dry test tube, it produce Lead oxide ($$PbO$$), Nitrogen dioxide ($$NO_2$$) and oxygen ($$O_2$$).

$$\bullet$$ The Lead oxide ($$PbO$$) is of yellow colour which is left as a residue.

$$\bullet$$ The gas which relights the glowing splint is oxygen gas ($$O_2$$).

$$\text{Additional information:}$$

$$\bullet$$ P = Lead Nitrate

Mention the physical states of the reactants and products of the following chemical reactions and balance the
equation.
$$NH_{3} + Cl_{2} \rightarrow N_{2} + NH_{4}Cl$$

$$\text{Part 1: The physical states of the reactant and products are given below:}$$

$$NH_3\rightarrow gas$$

$$Cl_2\rightarrow gas$$

$$N_2\rightarrow gas$$

$$NH_4Cl\rightarrow Solid$$

$$\bullet$$ In a chemical reaction, the physical state of reactants and products can be indicated by writing (s) for solid, (l) for liquid, (aq) for aqueous solution, and (g) for gaseous substance after their chemical formula or symbol.

$$\text{Part 2: Balanced chemical equations:}$$

The balanced chemical equation for the reaction given is as follows:

$$8NH_{3} (g) + 3Cl_{2}(g) \rightarrow N_{2} (g)+ 6NH_{4}Cl (s)$$

$$\bullet$$ According to the law of conservation of mass, total number of atoms on the reactant side should be equal to the total number of atoms in the product side.

$$ \bullet $$ Take about 100 ml of water in a beaker and dissolve a small quantity of sodium sulphate $$(Na_{2}SO_{4})$$.
$$ \bullet $$Take about
100ml of water in another beaker and dissolve a small quantity of barium chloride $$(BaCl_{2})$$. observe the colours of the
solutions obtained.
(a)What are the colours of the above solutions?
(b) Can you name the solutions obtained?(Add $$Na_{2}SO_{4}$$ solution to $$BaCl_{2}$$ solution and observe.)
(c)Do you observe any change on mixing these solutions?

(a)

Both these two solutions are colourless.

$$\bullet$$ When sodium sulphate is added to water, it dissociates into sodium and sulphate ions, forming a colourless solution.

$$\bullet$$ When barium chloride is added to water, it also forms a colourless solution.

(b)

When sodium sulphate solution $$(Na_2SO_4)$$ is combined with barium chloride$$(BaCl_2)$$ solution, it produces a barium sulphate $$(BaSO_4)$$ insoluble precipitate as well as soluble sodium chloride $$(NaCl)$$.

$$\bullet$$ The chemical reaction involved is as follows:

$$BaCl_2 + Na_2SO_4\rightarrow 2NaCl + BaSO_4$$

$$\bullet$$ This is a double displacement reaction as the two compounds exchange their ions to form two different compounds.

(c)

$$\bullet$$ In this reaction, barium sulphate and sodium chloride are formed when sodium sulphate and barium chloride react.

$$\bullet$$ The solution in water consists only of sodium chloride because sodium chloride dissolves in water while barium sulphate settles down and a white precipitate is formed (insoluble).

Following observations are recorded during a number of experiments on the substance P. When the substance P is heated, a reddish brown gas is evolved along with a gas which relights glowing wooden splint. A yellow residue is left in the test tube.
Name the reddish brown gas,

Reaction involved in this experiments is:-

$$Pb(NO_3)_2 \overset{\Delta }{\rightarrow} PbO \downarrow + 2NO_2(g) + O_2(g)$$

$$\bullet$$ Lead nitrate ($$Pb(NO_3)_2 $$), when heated strongly in a dry test tube, it produces Lead oxide ($$PbO$$), Nitrogen dioxide ($$NO_2$$) and oxygen ($$O_2$$).

$$\bullet$$ The Lead oxide ($$PbO$$) is of yellow colour which is left as a residue.

$$\bullet$$ The reddish brown gas is nitrogen dioxide ($$NO_2$$).

$$\text{Additional information:}$$

$$\bullet$$ P = Lead Nitrate

What is decomposition reaction? Explain it with suitable example.

The reaction in which a single compound breaks down into two or more than two elements or new compounds is called decomposition reaction.

$$H_2O_2\rightarrow H_2+O_2$$

Burning magnesium ribbon in the air to form magnesium oxide is an example of _______ (combination/decomposition) reaction.

Burning magnesium ribbon in the air to form magnesium oxide is an example of a combination reaction.

When the magnesium metal burns, it reacts with oxygen present in the air to form magnesium oxide. Oxygen and magnesium combine in a chemical reaction to form this compound.

After it burns, it forms a white powder of magnesium oxide.

Digestion of food is an example of ______ (physical/chemical) change.

During the process of digestion, the food is broken down into smaller molecules. The salivary glands present in our mouth help in the breakdown of the food. In this process, there is a formation of a new substance. Therefore, it is considered to be a chemical change.

Respiration is an example of ____________ (physical/chemical) change.

During respiration, oxidation of glucose takes place. The chemical reaction of oxidation of glucose is:

$$C_6H_{12}O_6 + 6 O_2 \rightarrow 6 CO_2 + 6 H_2O + Energy$$

Glucose reacts with oxygen to produce $$CO_2$$, $$H_2O$$ and energy.

We know that chemical change is a change in which new products are formed.

Therefore, we can say respiration is an example of chemical change.

Heat is released in _______ (endothermic/exothermic) reactions.

An exothermic reaction is a chemical reaction that releases energy in the form of light or heat. It is the opposite of an endothermic reaction.

Exothermic reaction Expressed in a chemical equation: Reactants $$\rightarrow$$ Products + Energy.

Heat is released in an exothermic reaction. The correct answer is exothermic.

________ reactions called the opposite of combination reactions.

Decomposition reactions are those in which a compound breaks down to form two or more substances. These reactions require a source of energy to proceed.

Thus, they are the exact opposite of combination reactions in which two or more substances combine to give a new substance with the release of energy.

Decomposition reaction : $$AB + Energy \rightarrow A+B$$

$$2H_2O(l) \overset{Electrolysis}{\rightarrow} 2H_2(g) + O_2(g)$$

Combination Reaction : $$A + B \rightarrow AB + Energy $$.

$$2H_2(g) + O_2(g) \rightarrow 2H_2O(l) + Energy$$.

So, the correct answer is Decomposition.

In a solution of silver nitrate, a copper plate was dipped. After some time, silver from the solution was deposited on the copper plate. Which metal is more reactive, copper or silver?

The initial silver nitrate solution is colourless. It turns blue when cupric nitrate is formed. This is an example of a displacement reaction. The reaction can be written as follows:

$$Cu (s) + 2AgNO_3 (aq) \rightarrow Cu(NO_3)_2 (aq) + 2Ag (s)$$

Hence, copper is more reactive than silver as it displaces silver from its solution.

Balance the following chemical equations:

(a) $$HN{ O }_{ 3 }+Ca{ \left( OH \right) }_{ 2 }\rightarrow Ca{ \left( N{ O }_{ 3 } \right) }_{ 2 }+{ H }_{ 2 }O$$

(b) $$NaOH+{ H }_{ 2 }S{ O }_{ 4 }\rightarrow { Na }_{ 2 }S{ O }_{ 4 }+{ H }_{ 2 }O$$

(c) $$NaCl+AgN{ O }_{ 3 }\rightarrow AgCl+NaN{ O }_{ 3 }$$

(d) $$Ba{ Cl }_{ 2 }+{ H }_{ 2 }S{ O }_{ 4 }\rightarrow BaS{ O }_{ 4 }+HCl$$

(a) $$2HNO_3 + Ca(OH)_2\rightarrow Ca(NO_3)_2 + 2H_2O$$

$$\bullet$$ It is a double displacement reaction since both molecules of the reactions are displaced to form new products.

$$\bullet$$ Nitric acid $$(HNO_3)$$ combines with calcium hydroxide $$[Ca(OH)_2]$$ to produce calcium nitrate$$[Ca(NO_3)_2]$$-a salt and water, which is a neutralization reaction.

$$\bullet$$ Hence, this reaction is both a double displacement as well as a neutralization reaction.

(b) $$2NaOH + H_2SO_4\rightarrow Na_2SO_4 + 2H_2O$$

$$\bullet$$ It is a double displacement reaction since both molecules of the reactions are displaced to form new products.

$$\bullet$$ Sulphuric acid $$(H_2SO_4)$$ combines with sodium hydroxide $$(NaOH)$$ to produce sodium sulphate$$(Na_2SO_4)$$-a salt and water, which is a neutralization reaction.

$$\bullet$$ Hence, this reaction is both a displacement as well as a neutralization reaction.

$$\bullet$$ This is a double displacement reaction since there is an exchange of ions between the reactants, forming new products.

(d) $$BaCl_2 + H_2SO_4\rightarrow BaSO_4 + 2HCl$$

$$\bullet$$ This is a double displacement reaction since there is an exchange of ions between the reactants, forming new products.

What do you see when a magnesium ribbon is burnt? Is magnesium oxidized or reduced in this reaction?

Magnesium burns very easily in the air to form magnesium oxide and this reaction needs an external source of energy. Magnesium metal is being oxidized to its metal oxide state, so it undergoes oxidation. This is an example of a combination reaction as well.

$$2Mg + O_2 \rightarrow 2MgO$$

Write word equations and then balanced equations for the reaction taking place when:
(a) Dilute sulphuric acid reacts with zinc granules.
(b) Dilute hydrochloric acid reacts with magnesium ribbon.
(c) Dilute sulphuric acid reacts with aluminium powder.
(d) Dilute hydrochloric acid reacts with iron filings.

a) Dilute sulphuric acid reacts with zinc granules to produce zinc sulphate and hydrogen gas

$$H_2SO_4(aq) + Zn(s) \rightarrow ZnSO_4(aq) + H_2(g)$$

(b) Dilute hydrochloric acid reacts with magnesium ribbon to produce magnesium chloride and hydrogen gas.

$$2HCl(aq) + Mg(s) \rightarrow MgCl_2(aq) + H_2(g)$$

$$3H_2SO_4(aq) + 2Al(s) \rightarrow Al_2(SO_4)_3 (aq) + 3H_2(g)$$

(d) Dilute hydrochloric acid reacts with iron filings to produce ferric chloride and hydrogen gas.

$$6HCl(aq) + Fe(s) \rightarrow 2FeCl_3(aq) + 3H_2(g)$$

What is the difference between displacement and double displacement reactions? Write equations for these reactions?

A single displacement reaction is a chemical reaction in which one element is substituted for another element in a compound, generating a new product.

For example,

$$2HCl(aq) + Zn(s) \rightarrow ZnCl_2(aq) + H_2(g)$$ is an example of a single-displacement reaction. The hydrogen atom in $$HCl$$ is replaced by $$Zn$$ atoms, and in the process hydrogen gas is formed.

A double-displacement reaction occurs when parts of two ionic compounds are exchanged, making two new compounds. A characteristic of a double-displacement equation is that there are two compounds as reactants and two different compounds as products.

An example is $$CuCl_2(aq) + 2AgNO_3(aq) \rightarrow Cu(NO_3)_2(aq) + 2AgCl(s)$$

Which reaction is this?
$$2NaHCO_{3}\xrightarrow {heat} Na_{2}CO_{3} + H_{2}O + CO_{2}$$

$$2NaHCO_{3}\xrightarrow {heat} Na_{2}CO_{3} + H_{2}O + CO_{2}$$

A decomposition reaction is a type of chemical reaction in which a single compound breaks down into two or more elements or new compounds. Hence it is an example of a decomposition reaction.

What causes rancidity? Name an antioxidant which prevents rancidity.

Rancidity is caused by oxidation of fats and oils present in food, marked by unpleasant odour or taste.
The substances which prevent oxidation of the food items are called antioxidants. Nitrogen is a popular antioxidant used by potato chips manufacturers.

Write one difference between displacement and double displacement reactions.

A displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound. Both metals and non-metals take part in displacement reactions.

A double displacement reaction is a type of chemical reaction where two compounds react, and the positive ions (cation) and the negative ions (anion) of the two reactants switch places, forming two new compounds or products.

What happens when:
i) $$CuS{ O }_{ 4 }\left( aq \right) +Fe\left( s \right) \rightarrow $$?
ii) $$Zn\left( s \right) +{ H }_{ 2 }S{ O }_{ 4 }\left( l \right) \rightarrow $$?
iii) $$Na\left( s \right) +{ O }_{ 2 }\left( g \right) \rightarrow $$?

(i) It is a displacement reaction. It is as follows : $$CuS{ O }_{ 4 }(aq)+2Fe(s)\longrightarrow { Fe }_{ 2 }{ (S{ O }_{ 4 }) }_{ 3 }+3Cu(s)$$

(ii) Zinc reacts with dilute sulphuric acid to give zinc sulphate with the evolution of hydrogen gas. The reaction is as follows: $$Zn+{ H }_{ 2 }S{ O }_{ 4 }\longrightarrow ZnS{ O }_{ 4 }+{ H }_{ 2 }\uparrow $$

(iii) Small pieces of sodium burn in the air with often little more than an orange glow. Using larger amounts of sodium or burning it in oxygen gives a strong orange flame. A white solid mixture of sodium oxide and sodium peroxide is formed.

The equation for the formation of oxide is:.

$$4Na+{ O }_{ 2 }\longrightarrow 2{ Na }_{ 2 }O$$

The peroxide equation is:

$$2Na+{ O }_{ 2 }\longrightarrow { Na }_{ 2 }{ O }_{ 2 }$$

Explain rancidity.

Rancidity is a very general term and in its most general meaning, it refers to the spoilage of food. It is a condition produced by aerial oxidation of fat present in foods and other products and is marked by unpleasant odour or flavour.

Identify $$X$$, $$Y$$ and $$Z$$ in the following equations :
i) $$Cu + C{O}_{2} \xrightarrow {\quad moisture\quad }$$ Green compound $$ \left( X \right)$$
ii) $$ Ag + Y \xrightarrow {\quad air\quad }$$ Black compound $$ \left( { Ag }_{ 2 }S \right) $$
iii) $$Fe S{ O }_{ 4 } \xrightarrow { \quad heat\quad } { Fe }_{ 2 }{ O }_{ 3 }+S{ O }_{ 3 }+Z$$

(i) A reaction of copper with carbon dioxide and moisture forms copper(II) carbonate which is green in colour. Reaction is as follows:

$$Cu+C{ O }_{ 2 }\xrightarrow { \quad Moisture\quad } CuC{ O }_{ 3 }$$

(ii) Silver sulfide ($${ Ag }_{ 2 }S$$) is the sulfide of silver. Silver sulfide is insoluble in all solvents but is degraded by strong acids. It has an ionic bond, as it is made up of silver (electronegativity = 1.98) and sulfur (electronegativity = 2.58). $$2Ag+S\xrightarrow { \quad Air\quad } \quad { Ag }_{ 2 }S$$.
(iii) On heating, ferrous sulphate crystals lose water and anhydrous ferrous sulphate is formed. So their colour changes from light green to white. On further heating, anhydrous ferrous sulphate decomposes to form ferric oxide, sulphur dioxide, and sulphur trioxide. $$FeS{ O }_{ 4 }\xrightarrow { \quad Heat\quad } { Fe }_{ 2 }{ O }_{ 3 }+S{ O }_{ 3 }+S{ O }_{ 2 }$$

Give the name of the gas that evolved when sodium hydroxide reacts with zinc metal. Write the equation also.

Zinc will react with sodium hydroxide to form sodium zincate and hydrogen gas will evolve. The reaction is as given below:

$$2NaOH + Zn \longrightarrow 2NaZn{ O }_{ 2 } + { H }_{ 2 }\uparrow $$

Write the balanced chemical equation when zinc reacts with dilute nitric acid.

Zinc reacts with dilute nitric acid to form zinc nitrate and hydrogen gas.

The balanced chemical equation is as shown:

$$\displaystyle Zn+2HN{ O }_{ 3 }\rightarrow Zn{ \left( N{ O }_{ 3 } \right) }_{ 2 }+{ H }_{ 2 }\uparrow$$

(a) What is a displacement reaction?
(b) Identify A in the following reactions.
(i) $$Zn+CuSO_4\rightarrow A+Cu$$
(ii) $$Na_2SO_4+BaCl_2\rightarrow A+2NaCl$$.

(a) Displacement reaction is a chemical reaction in which a more reactive element displaces a less reactive element from its compound.
(b)

(i) $$Zn+CuS{ O }_{ 4 }\longrightarrow ZnS{ O }_{ 4 }+Cu$$. So, the product A in the reaction is $$ZnSO_4$$.
(ii) $${ Na }_{ 2 }S{ O }_{ 4 }+Ba{ Cl }_{ 2 }\longrightarrow BaS{ O }_{ 4 }+2NaCl$$. The product A in the reaction is $$BaSO_4$$.

Choose the correct answer from the four alternatives given in the brackets:
$$Zn+2HCl\longrightarrow Zn{ Cl }_{ 2 }+{ H }_{ 2 }\uparrow $$
The above reaction is an example of _______.
(Combination reaction, Double displacement reaction, Displacement reaction, Decomposition reaction)

The above-given reaction is an example of a displacement reaction. Here the more reactive metal zinc displaces the less reactive metal hydrogen and zinc chloride is obtained as the product.

Explain an experiment with a chemical equation to establish that iron is more reactive than silver.

In a beaker filled with silver nitrate solution, dip a new iron nail. Remove the nail after some time. You will observe that the iron nail is coated with silver. This indicates that iron has displaced silver ions from silver nitrate. Hence, iron is more reactive than silver.
$$\displaystyle Fe + 2AgNO_{3}\rightarrow Fe(NO_{3})_{2} + 2Ag ^+$$

What type of chemical reaction takes place when:
(a) lime stone is heated.
(b) a magnesium ribbon is burnt in air.

(a) When the limestone is heated, it undergoes decomposition reaction as:

$$ CaCO_3 \overset{\Delta }{\rightarrow} CaO + CO_2 $$

(b) When magnesium ribbon is burnt in air it undergoes combination reaction with oxygen.

$$ 2Mg + O_2 \rightarrow 2MgO $$

Write the balanced chemical reaction for the following and identify the type of reaction in each case.
(A) $$Magnesium_{(a)} + Iodine_{(g)} \rightarrow Magnesium\ iodide_{(s)}$$
(B) $$Zinc_{(s)} + Hydrochloric\ acid_{(aq)} \rightarrow Zinc\ chloride_{(aq)} + Hydrogen_{(g)}$$

(A) $$ 2Mg_{(s)}+ I_{{2}(g)} \rightarrow 2MgI_{(s)}$$

It is a combination reaction.

(B) $$ Zn_{(s)} + 2HCl \rightarrow ZnCl_{{2}{(aq)}} + H_{{2}{(g)}} $$

It is a displacement reaction in which the more reactive metal Zn displaces hydrogen.

Divide the following redox reactions into oxidation and reduction half reactions.
$$Zn + Cu^{2+} \rightarrow Zn^{2+} + Cu$$

Oxidation : $$Zn \rightarrow Zn ^{2+}+2e^-$$

Reduction : $$Cu^{2+}+2e^- \rightarrow Cu$$

What is observed when a solution of sodium sulphate is added to a solution of barium chloride taken in a test tube? Write equation for the chemical reaction involved and name the type of reaction in this case.

These two solutions react to form a white insoluble precipitate.

$$BaCl_2 + Na_2SO_4 \rightarrow 2NaCl + BaSO_4 \downarrow$$

This is a double displacement reaction as the two compounds exchange their ions to form two different compounds.

State the law which is followed in balancing a chemical equation.

Law which is followed in balancing a chemical equation is "Law of conservation of mass'' which states that matter con not be created or distroyed and both sides (reactant side and product side) should be balanced by coefficient to ensure that this law is followed.

Taking into consideration the relationship in the first pair, complete the second pair.
$$2H_2+O_2\rightarrow 2H_2O :$$ Combination Reaction $$:$$ $$:$$ $$CaCO_3\rightarrow CaO+CO_2$$ $$:$$ ___________.

The reaction, $$CaCO_3\rightarrow CaO+CO_2$$ is a Decomposition reaction.
Decomposition reactions are a type of chemical reaction that involves breaking down a compound into smaller compounds or individual elements. These reactions often involve the input of energy in the form of heat, light, or electricity to break down the compounds.

Give an example of a double displacement reaction.

$$ 2KBr(aq) + BaI_2(aq) \rightarrow 2KI (aq) + BaBr_2 (aq) $$

Write a balance chemical equation of the following:
$$FeSO_4(s) \xrightarrow{heat} Fe_2O_3(s) + SO_2(g) + SO_3(g)$$

Given chemical equation: $$FeSO_4 (s)\longrightarrow Fe_2O_3+SO_2+SO_3$$

Balancing $$'Fe'$$, we get:

$$2FeSO_4 (s)\quad \xrightarrow { heat }\quad Fe_2O_3 (s)+SO_2 (g)+SO_3 (g)$$

This is the balanced chemical equation.

Write balanced chemical equations for the following word equation:
Zinc + Steam $$\rightarrow $$ Zinc oxide + Hydrogen

$$Zinc + Steam \longrightarrow Zinc\ oxide + Hydrogen$$
$$Zn + H_2O \longrightarrow ZnO + H_2$$
Above reaction is balanced as number of atoms of elements in reactant and product are equal.

State an important use of decomposition reaction.

Decomposition reaction is used in manufacture of cement or calcium oxide.

$$CaCO_3 \xrightarrow{Heat} CaO + CO_2$$

Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. Write balanced chemical equation for this reaction.

Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

Chemical equation:

$$2K(s) + 2H_2O(l) \rightarrow 2KOH(aq)+H_2(g)$$

Complete the following reactions and give name of the products.
$$CuSO_{4}(aq)+Pb(s)\longrightarrow .......+.........$$

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When silver nitrate solution is added to a solution of $$A$$, a white precipitate, insolube in nitric acid is formed.

When silver nitrate($$AgNO_3$$) solution is added to a solution of $$NaCl$$A, a white precipitate of silver chloride ($$AgCl$$) is formed which is insolube in nitric acid .

$$AgNO_3 +NaCl \rightarrow NaNO_3 + AgCl$$

State any one observation for each of the following :
(i) Dilute Hydrochloric acid is added to Silver nitrate solution.
(ii) Concentrated Nitric acid id added to Copper turnings.
(iii) Mixture of Ammonium Chloride and Sodium Hydroxide is heated.
(iv) Ammonium hydroxide solution is added in excess to copper sulphate solution.
(v) NaOH solution is added to calcium nitrate solition.

$$(i)$$ When dilute hydrochloric acid is added to the silver nitrate solution, a white precipitate of silver chloride is formed and nitric acid is also formed. The chemical equation for the reaction is given below.

$$HCl+AgNO_{3}\rightarrow \underset{\text{white ppt}}{AgCl} \downarrow +HNO_{3}$$

$$(ii)$$ When concentrated nitric acid is added to Copper turnings, reddish-brown fumes of nitrogen dioxide gas are evolved. The chemical equation for the reaction is given below.

$$Cu+4HNO_{3}\rightarrow Cu\left(NO_{3}\right)_{2}+2NO_{2}\uparrow+2H_{2}O$$

$$(iii)$$ When a mixture of ammonium chloride and sodium hydroxide is heated, a pungent-smelling gas, ammonia is evolved. Also, sodium chloride and water are formed. The chemical equation for the reaction is given below.

$$NH_{4}Cl+NaOH\rightarrow NaCl+NH_{3}\uparrow+H_{2}O$$

$$(iv)$$ When ammonium hydroxide $$(NH_4OH)$$ is added in a small quantity to copper sulphate solution $$(CuSO_4)$$, a pale blue precipitate is formed which dissolves in excess of ammonium hydroxide to give a deep blue or inky blue solution.

$$CuSO_4+2NH_4OH\rightarrow \underset{Pale\ blue \ ppt}{Cu(OH)_2}+(NH_4)_2SO_4$$

$$Cu(OH)_2+2NH_4OH\rightarrow \underset{Prussian \ blue \ solution}{[Cu(NH_3)_4}](OH)_2+4H_2O$$

$$(v)$$ When sodium hydroxide (NaOH) is added to the calcium nitrate solution, it forms a white precipitate of calcium hydroxide. The chemical equation for the reaction is given below.

$$Ca\left(NO_{3}\right)_{2}+2NaOH\rightarrow \underset{white \ ppt}{Ca\left(OH\right)_{2}}\downarrow+2NaNO_{3}$$

Explain Balanced equation with examples.

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(a) A white powder is added while baking breads and cakes to make them soft and fluffy. Write the name of the powder. Name the main ingredients. Explain the function of each ingredient.
(b) Write the chemical reaction taking place when the powder is heated during baking.

$$\textbf{Part (a): Determine the main ingredients and the function of baking powder}$$

$$\bullet$$ Baking powder is a white powder that is used while baking breads and cakes to make them soft and fluffy.

$$\bullet$$ The main ingredients of baking powder are baking soda and tartaric acid. It is a mixture of both these ingredients.

$$\bullet$$ When baking powder mixes with water (present in dough made for baking cake or bread), then sodium hydrogen carbonate (aka baking soda with formula $$NaHCO_3$$) reacts with hydrogen ion of tartaric acid and evolve carbon dioxide gas that makes the cake fluffy and soft.

$$\textbf{Part (b): Write the chemical reaction for heating the baking powder}$$

$$\bullet$$ The chemical reaction taking place when the powder is heated during baking is as follows:

$$2NaHCO_3\overset{Heat}{\longrightarrow} Na_2CO_3+CO_2+H_2O$$

Baking soda on heating produces sodium carbonate, carbon dioxide and water.

Fill in the blanks:
In some chemical reactions an insoluble ................... is formed when two solutions are mixed.

In some chemical reactions an insoluble precipitate is formed when two solutions are mixed.

Write balanced chemical equations for the following word equation:
Potassium chlorate $$\rightarrow $$ Potassium chloride + Oxygen

Potassium chlorate $$\rightarrow $$ Potassium chloride + Oxygen

$$2KClO_{3} \rightarrow 2KCl + 3O_{2} $$

Reactant Side Product Side

$$K$$ $$2$$ $$2$$

$$Cl$$ $$2$$ $$2$$

$$O$$ $$6$$ $$6$$

Hence the reaction is balanced

When ammonium chloride is mixed with barium hydroxide in a beaker, it becomes cold.

When ammonium chloride is mixed with barium hydroxide in a beaker, an endothermic reaction takes place which is characterised by fall in temperature.

So beaker becomes cold. This reaction is a highly endothermic reaction.

Write balanced chemical equations for the following word equation:
Copper +Oxygen $$\rightarrow $$ Copper (II) oxide

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How to balance a reaction?

We can balance a reaction by equating the number of atoms on both sides of the arrow, i.e. the reactant side and the product side.

For example, below is an unbalanced reaction:

$$Al + O_2 \rightarrow Al_2O_3$$

We can balance it by equating number of aluminium and oxygen atoms on the reactant and product side as follows:

$$4Al + 3O_2 \rightarrow 2Al_2O_3$$

Give an example of a double displacement reaction other than the reaction of barium chloride with sodium sulphate.

The example of double displacement reaction other than the reaction of barium chloride with sodium sulphate is as follows:

A white precipitate of lead chloride ($$PbCl_2$$) is formed when a solution of hydrochloric acid (HCl) is added to a solution of lead nitrate $$(Pb(NO_3)_2)$$.

$$\bullet$$ The chemical reaction involved is as follows:

$$Pb(NO_3)_2+ 2HCl\rightarrow PbCl_2 + 2HNO_3$$

$$\bullet$$ A precipitate of lead chloride is formed when $$Pb^{+2}$$ ions from lead nitrate combine with $$2Cl^{-}$$ ions from hydrochloric acid.

$$\bullet$$ The two reactants, lead nitrate and hydrochloric acid, exchanging the ions, making this a double displacement reaction.

$$\text{Additional information}$$

The term "displacement reaction" refers to a reaction in which a part of one reactant is displaced by another reactant.

In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.

$$\bullet$$ The reaction involved, in the refining of silver is:-

$$2AgNO_3(aq) + Cu(s) \rightarrow 2Ag + Cu(NO_3)_2$$

$$\bullet$$ In the reaction, copper (Cu) is displacing silver from its nitrate solution ($$AgNO_3$$) as it is more reactive compared to silver.

$$\bullet$$ Copper itself form a compound by reacting with nitrate ($$NO_3^-$$) and refined silver metal is obtained as another product.

We can store copper sulphate solution in a silver vessel but not silver nitrate solution in a copper vessel. Give reason.

$$\textbf{Solution}$$

$$\bullet$$We store copper sulphate solution in a silver vessel because silver is less reactive than copper. So no displacement reaction occurs.

$$\bullet$$Copper is above silver in the electrochemical series and is thus more reactive than silver.

$$\bullet$$So, copper displaces silver from silver nitrate. Hence, we cannot store $$AgNO_3$$ solution in a copper vessel.

$$\bullet$$$$Cu + 2AgNO_3 \to Cu(NO_3)_2 + 2Ag$$

What is the products formed when zinc reacts with dilute nitric acid?

$$\textbf{Solution}$$

$$\bullet$$Zinc reacts with dilute Nitric acid to produce Zinc nitrate, nitric oxide and water

$$3Zn+8HNO_{3} (dil.)\rightarrow \ 3Zn\left(NO_{3}\right)_{2} + 2NO+4H_{2}O$$

$$\bullet$$Zinc reacts with concentrated Nitric acid to produce Zinc nitrate, nitrogen dioxide and water.

$$Zn+4HNO_{3} (conc.)\rightarrow \ Zn\left(NO_{3}\right)_{2}+ 2NO_{2}+2H_{2}O$$

What does the symbol ($$aq$$) represent in a chemical equation?

The symbol $$(aq)$$ represents an aqueous solution in a chemical reaction. An aqueous solution is a solution in which the solvent is water.

For example:

$$ Na(s)+ H_2O (l) \rightarrow H_2(g) + NaOH(aq)$$

This shows that $$NaOH$$ formed is dissolved in water.

Observe the diagram showing a copper rod kept immersed in silver nitrate solution.
a. What is the colour change of the solution?
b. Write the balanced chemical equation for the reaction.

a. Copper metal is more reactive than silver metal thus when copper rod is kept immersed in silver nitrate solution for some time, it displaces silver from silver nitrate solution and grey solid crystal of $$Ag$$ metal are seen growing on the copper rod and the solution turns blue in colour.

b. $${Cu}_{\left( s \right)} + 2 {AgN{O}_{3}}_{\left( aq. \right)} \longrightarrow {Cu{\left( N{O}_{3} \right)}_{2}}_{\left( aq. \right)} + 2 {Ag}_{\left( s \right)}$$

Write symbolic representation for the following word equations and balance them:
Calcium oxide + Water $$\rightarrow$$ Calcium hydroxide

Calcium oxide + Water $$\rightarrow$$ Calcium hydroxide

$$CaO + H_2O \rightarrow Ca(OH)_2$$

Which of the following reactions will not occurs? Why not?

(a) $$ MgSO_4 (aq) + Cu (s) \rightarrow CuSO_4(aq) +Mg (s) $$

(b) $$ CuSO_4(aq) +Fe(s) \rightarrow FeSO_4(aq) +Cu(s) $$

(c) $$ MgSO_4(aq) +Fe(s) \rightarrow FeSO_4(aq) +Mg(s) $$

Reaction (a) will not occur because Cu is less reactive than Mg.

Reaction (b) will occur because Cu is less reactive than Fe.

Reaction (c) will also not occur because Fe is less reactive than Mg.

Correct and balance the following equation:

$$Ca+H_2O\rightarrow CaOH+H$$

$$ Ca(s) + 2H_2O(l) \rightarrow Ca(OH)_2(aq) +H_2(g) $$

The number of atoms of $$Ca$$ (1 atom), $$ H$$ (4 atoms), and $$ O $$ (2 atoms) is the same on both sides.

Aluminium hydroxide reacts with sulphuric acid to form aluminium sulphate and water. Write a balanced equation for this reaction.

Aluminium hydroxide reacts with sulphuric acid to form aluminium sulphate and water.

Reaction: $$2Al(OH)_3(aq)+3H_2SO_4(aq) \rightarrow Al_2(SO_4)_3(aq)+6H_2O(l)$$

a) Why are decomposition reactions called the opposite of combination reactions? Explain with equations of these reactions.

b) Express the following facts in the form of a balanced chemical equation:
"When a strip of copper metal is placed in a solution of silver nitrate, metallic silver is precipitated and a solution containing copper nitrate is formed".

Those reactions in which a compound splits up into two or simpler substances are known as decomposition reactions.

Example: When calcium carbonate is heated, it decomposes to give calcium oxide and carbon dioxide.

$$CaCO_3\xrightarrow[(Decomposition)]{Heat}CaO$$ $$+$$ $$CO_{2(g)}$$

Calcium carbonate Calcium oxide Carbon dioxide

(Limestone) (Lime)

They are called opposite of combination reactions because, in a combination reaction, two or more substances combine to form a single substance.

Example: Magnesium and oxygen combine when heated formed magnesium oxide.

a) $$2Mg_{(s)} +O_2\overset{Combination}{\longrightarrow}2MgO_{(s)}$$

Magnesium Oxygen Magnesium Oxide

b) $$Cu_{(s)} +2AgNO_{3(aq)} \rightarrow Cu(NO_3)_{2(aq)} +2Ag_{(s)}$$

Give one example of a chemical reaction.

A chemical reaction is a process in which one or more substances, the reactants, are converted to one or more different substances, the products.

For example, oxygen and magnesium combine in a chemical reaction to form a white powder of magnesium oxide.

$$2Mg +O_2 \rightarrow 2MgO$$

Fill in the blank with suitable words:

Anti-oxidants are often added to fat-containing foods to prevent .......... due to oxidation.

Anti-oxidants are often added to fat-containing foods to prevent rancidity due to oxidation.

Which of the following is a combination and which is a displacement reaction?

a) $$Cl_2+2KI \rightarrow 2KCl+I_2$$

b) $$2K+Cl_2 \rightarrow 2KCl$$

a) Displacement reaction as chlorine displace iodine from the compound.

b) Combination reaction as potassium combine with chlorine to form potassium chloride.

Correct and balance the following equation:
$$N+H_2 \rightarrow NH_3$$

$$N_2(g) +3H_2(g) \rightarrow 2NH_3(g)$$

Since nitrogen gas exists as $$N_2$$, we correct $$N$$ to $$N_2$$.

We write the state of the reactants and products in brackets (g).

We balance 2 nitrogen atoms and 6 hydrogen atoms on the left and the right by adding respective coefficients (3, 2).

Balance the following chemical reaction:

$$MnO_2+HCl \rightarrow MnCl_2+Cl_2+H_2O$$

Balanced chemical reaction is:

$$MnO_2+4HCl \rightarrow MnCl_2+Cl_2+2H_2O$$

When a green iron salt is heated strongly, its colour finally changes to brown and odour of burning sulphur is given out.
(i) Name the iron salt and name the type of reaction that takes place during the heating of iron salt.
(ii) Write a chemical equation for the reaction involved.

a) The iron salt is ferrous sulphate $$(FeSO_4).$$

b) The type of reaction that takes place during the heating of iron salt is decomposition reaction.

c) The balanced chemical equation for the reaction involved is:

$$2FeSO_4(s)\xrightarrow[Decomposition]{Heat}Fe_2O_3(s)+SO_2(g)+SO_3(g)$$

Define rancidity.

The oxidation of oils or fats in food resulting in a bad taste and smell is called rancidity.

Why does food spoil when kept for a very long time?

When food is kept for a very long time, it gets oxidised and becomes rancid. This happens especially with food that has a high quantity of fat or oil. We can preserve food and prevent it from going rancid by storing it in an airtight container.

Why is photosynthesis considered an endothermic reaction?

Photosynthesis is an endothermic reaction because energy in the form of sunlight is absorbed during the process of photosynthesis by green plants.

What is meant by rancidity and how it can be prevented?

When fats and oils are oxidized in the presence of air, they become rancid and their smell and taste changes.This phenomenon is called rancidity.

Rancidity can be prevented by

i. Using antioxidants- Substances that prevent oxidation are called antioxidants. They are added to foods containing fats and oils.

For example, nitrogen gas is filled in the packets of chips to prevent them from oxidation.

ii. Keeping food in air-tight containers to slow down the process of oxidation.

Name the type of chemical reaction represented by the following equation:
(i)$$CaO+H_{2}O \longrightarrow Ca(OH)_{2}$$
(ii)$$3BaCl_{2}+Al_{2}(SO_{4})_{3} \longrightarrow 2AlCl_{3}+3BaSO_{4}$$
(iii)$$2FeSO_{4} \xrightarrow[]{Heat} Fe_{2}O_{3}+SO_{2}+SO_{3}$$

(i) Combination reaction.
(ii) Double displacement reaction.
(iii) Decomposition reaction.

"We need to balance skeletal chemical equation." Give reason to justify this statement.

Balanced chemical equation: A chemical equation in which the number of atoms of reactants are equal to the number of atoms of products is called a balanced equation.

We need to balance a skeletal chemical equation because:

$$I.$$ According to the law of conservation of mass, mass (or atoms) are neither created nor destroyed in chemical reactions.

$$II.$$ It means the total mass of the products formed in a chemical reaction must be equal to the mass of reactants consumed.

Identify the oxidising agent (oxidant) in the following reactions
$$\text { (a) } P b_{3} O_{4}+8 H C l \rightarrow 3 P b C l_{2}+C l_{2}+4 H_{2} O$$

$$P b_{3} O_{4}$$

Write the balanced chemical equations for the following reaction and identify the type of reaction.
Thermit reaction, iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide.

$$\mathrm{Fe}_{2} \mathrm{O}_{3}+2 \mathrm{Al} \rightarrow 2 \mathrm{Fe}+\mathrm{Al}_{2}+\text { Heat }+\text { light }$$

This is a redox reaction.

Identify the reducing agent in the following reaction-
$$ F e_{2} O_{3}+3 C O \rightarrow 2 F e+3 C O_{2}$$

$$CO$$ gains oxygen forming $$CO_2$$ in the reaction. Therefore CO is being oxidized in the reaction. Hence CO acts as reducing agent.

Identify the oxidising agent (oxidant) in the following reactions
$$\text { (e) } 3 F e+4 H_{2} O \rightarrow F e_{3} O_{4}+4 H_{2}$$

$$H_{2} O$$

Identify the oxidising agent (oxidant) in the following reactions
$$\text { (c) } C u S O_{4}+Z n \rightarrow C u+Z n S O_{4}$$

$$C u S O_{4}$$

Identify the oxidising agent (oxidant) in the following reactions
$$\text { (b) } 2 M g+O_{2} \rightarrow 2 M g O$$

$$O_{2}$$

Identify the reducing agent in the following reactions
$$2 H_{2}+O_{2} \rightarrow 2 H_{2} O$$

In the given reaction $$H_2$$ gains oxygen therefore it is being oxidized in the reaction hence act as reducing agent.

Write a balanced chemical equation for each of the following reactions and also classify them.
(b) A piece of sodium metal is added to absolute ethanol to form sodium ethoxide and hydrogen gas.

$$Na + C_{2}H_{5}OH \rightarrow C_{2}H_{5}Na + \dfrac{1}{2}H_{2}$$
Displacement Reaction

Give the characteristic tests for the following gas.
$$CO_{2}$$

When carbon dioxide is passed into lime water, the lime water turns milky. This is the characteristic test for carbon dioxide.
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Give the characteristic tests for the following gas.
$$O_{2}$$

When a burning matchstick is brought near oxygen, the matchstick burns even more brightly. This is the characteristic test for oxygen.

Give the characteristic tests for the following gas.
$$SO_{2}$$

Sulphur dioxide can be identified from its smell. It smells like rotten eggs.

On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed.
Identify the type of reaction.

Balanced chemical equation:

$$2 C u\left(N O_{3}\right)_{2}(s) \stackrel{H e a t}{\longrightarrow} 2 C u O(s)+O_{2}(g)+4 N O_{2}(g)$$

Hence, this is a decomposition reaction.

Give the characteristic tests for the following gas.
$$H_{2}$$

When a burning matchstick is brought near hydrogen gas, the matchstick burns with a pop sound.

You are provided with two containers made up of copper and aluminium. You are also provided with solutions of dilute HCl, dilute $$H N O_{3}, Z n C l_{2}$$ and $$H_{2} O .$$ In which of the above containers these solutions can be kept?

Copper is a noble metal. It does not react with hydrochloric acid or with nitric acid. But aluminium is more reactive than copper. So, these acids should be kept in copper container.

Copper is less reactive than zinc and hence zinc chloride solution can be kept in copper container. But aluminium is more reactive than zinc and hence zinc chloride solution can not be kept in an aluminium container.

For keeping water, both the containers can be used. However, copper is better.

On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed.
Write a balanced chemical equation of the reaction.

Balanced chemical equation:

$$2 C u\left(N O_{3}\right)_{2}(s) \stackrel{H e a t}{\longrightarrow} 2 C u O(s)+O_{2}(g)+4 N O_{2}(g)$$

A magnesium ribbon is burnt in oxygen to give a white compound X accompanied by emission of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound Y.
(a) Write the chemical formulae of X and Y.
(b) Write a balanced chemical equation, when X is dissolved in water.

(a) $$X$$ is $$M g O, Y$$ is $$M g_{3} N_{2}$$

(b) $$M g O+H_{2} O \rightarrow M g(O H)_{2}$$

Identify the oxidising agent (oxidant) in the following reactions
$$\text { (f) } C u O+H_{2} \rightarrow C u+H_{2} O$$

CuOCuO

Write symbolic representation for the following word equations and balance them:
Aluminium + Chlorine $$\rightarrow$$ Aluminium chloride

Aluminium + Chlorine $$\rightarrow$$ Aluminium chloride

$$Al + Cl_2 \rightarrow AlCl_3$$

Now, after balancing the above chemical equation we get;
$$2Al + 3Cl_2 \rightarrow 2AlCl_3$$

On heating calcium carbonate gets converted into calcium oxide and carbon dioxide. Can you prepare one acidic and one basic solution by using the products formed in the above process? If so, write the chemical equation involved.

Acidic and basic solutions can be prepared by dissolving the products of the above process in water.

Calcium oxide will form a basic solution.

$$CaO + H_{2}O \rightarrow Ca(OH)_{2}$$ (Basic solution)

Carbon dioxide will form an acidic solution.

$$C0_{2} + H_{2}0 \rightarrow H_{2}CO_{3}$$ (Acidic solution)

A gas is evolved when ethanol reacts with sodium. Name the gas evolved and also write the balanced chemical equation of the reaction involved.

When ethanol reacts with sodium, then hydrogen gas is evolved. This reaction can be given by following equation:
$$2Na + 2CH_3CH_2OH \rightarrow 2CH_3CH_2ONa + H_2$$

Give the following a suitable word.
The smallest unit of matter which takes part in a chemical reaction.

According to Dalton's atomic theory, the atom is the smallest unit of matter that can take part in a chemical reaction.

What are the chemical reactions?

Chemical reactions are defined as the process in which one or more substances are converted into one or more different products.

Examples: iron and oxygen combine to form rust, vinegar and baking soda combine to form sodium acetate.

Chemical reactions are of the following types:

Combination reaction
Decomposition reaction
Displacement reaction
Double displacement reaction
Oxidation and reduction reaction

What information do you get from the equation $$H_2 + Cl_2 \rightarrow 2HCl$$ ?

(a) Hydrogen and chlorine molecules are the reactants.
(b) They are in gaseous form.
(c) The product is hydrogen chloride gas.
(d) Two molecules of hydrogen chloride are formed.

Write the balanced chemical equation for the following word equation:
Potassium permanganate + Hydrochloric acid $$\rightarrow$$ Potassium chloride + Manganese chloride + Chlorine + Water

$$2KMnO_4 + 16HCl \rightarrow 2KCl + 2MnCl_2 + 5Cl_2 + 8H_2O$$

Write the balanced chemical equations of the following word equation:
Aluminium + sodium hydroxide + water $$\rightarrow$$ sodium meta aluminate + hydrogen

$$2Al + 2NaOH + 2H_2O \rightarrow 2NaAlO_2 + 3H_2$$

Write the balanced chemical equations of the following word equation:
Potassium dichromate + Hydrochloric acid $$\rightarrow$$ Potassium chloride + Chromium chloride + Water + Chlorine

$$K_2Cr_2O_7 + 14HCl \rightarrow 2KCl + 2CrCl_3 + 7H_2O + 3Cl_2$$

Write the balanced chemical equations of the following word equation:
Barium chloride + Sulphuric acid $$\rightarrow$$ Barium Sulphate + Hydrochloric acid

Balanced chemical equation is,

$$BaCl_2 + H_2SO_4 \rightarrow BaSO_4 + 2HCl$$

Balance the following equations
$$P + HNO_3 \rightarrow NO_2 + H_2O + H_3PO_4$$

$$P + 5HNO_3 \rightarrow 5NO_2 + H_2O + H_3PO_4$$

Divide the following redox reactions into oxidation and reduction half reactions.
$$Cl_{2} + 2Br^{-} \rightarrow Br_{2} + 2Cl^{-}$$

The given reaction is as follows:

$$Cl_{2} + 2Br^{-} \rightarrow Br_{2} + 2Cl^{-}$$

The loss of electrons is considered oxidation. It occurs at the anode.

The oxidation half-reaction is as follows:

$$2Br^{-}\rightarrow Br_{2}+2e^{-}$$

The gain of electrons is considered as reduction. It occurs at the cathode.

The reduction half-reaction is as follows:

$$Cl_{2}+2e^{-}\rightarrow 2Cl^{-}$$

Divide the following redox reactions into oxidation and reduction half reactions.
$$2Cu^{+} \rightarrow Cu + Cu^{2+}$$

The given reaction is as follows:

$$2Cu^{+}\rightarrow Cu+Cu^{2+}$$

The loss of electrons is considered oxidation. It occurs at the anode.

The oxidation half-reaction is as follows:

$$Cu^{+}\rightarrow Cu^{2+}+e^{-}$$

The gain of electrons is considered as reduction. It occurs at the cathode.

The reduction half-reaction is as follows:

$$Cu^{+}+e^{-}\rightarrow Cu$$

Write the balanced chemical equations of the following word equation:
Aluminium sulphate + sodium hydroxide $$\rightarrow$$ sodium sulphate + sodium meta aluminate + water

$$Al_2(SO_4)_3 + 8NaOH \rightarrow 3Na_2SO_4 + 2NaAlO_2 + 4H_2O$$

Write the balanced chemical equations of the following word equation:
Aluminium carbide + water $$\rightarrow$$ aluminium hydroxide + methane

$$Al_4C_3 + 12H_2O \rightarrow 4Al(OH)_3 + 3CH_4$$

Addition of oxygen is known as __________.

Addition of oxygen is known as oxidation.

For example,

$$2Mg + O_2 \rightarrow 2MgO$$

Write the balanced chemical equation for the following word equation:
Sulphur + Nitric acid $$\rightarrow$$ Sulphuric acid + Nitrogen dioxide + Water

Word equation:

$$Sulphur + Nitric\ acid \rightarrow Sulphuric\ acid + Nitrogen\ dioxide + Water$$

Chemical equation (unbalanced):

$$S + HNO_3 \rightarrow H_2SO_4 + NO_2 + H_2O$$

Chemical equation (balanced):

$$S + 6HNO_3 \rightarrow H_2SO_4 + 6NO_2 + 2H_2O$$

What kind of chemical reaction is synthesis? Support your answer by an example.

Synthesis is a combination reaction.

In the above reaction, substances A and B combine to give a molecule of a new substance, AB.

Carbon burns in oxygen to form a gaseous compound, carbon dioxide.

$$C + O_2 \overset{∆}\rightarrow CO_2$$

Divide the following redox reaction into oxidation and reduction half reactions.
$$Zn+Cu^{2+}\rightarrow Zn^{2+}+Cu$$

The given reaction is as follows:

$$Zn + Cu^{2+} \rightarrow Zn^{2+} + Cu$$

The loss of electrons is considered oxidation. It occurs at the anode.

The oxidation half-reaction is as follows:

$$Zn\rightarrow Zn^{2+}+2e^{-}$$

The gain of electrons is considered as reduction. It occurs at the cathode.

The reduction half-reaction is as follows:
$$Cu^{2+}+2e^{-}\rightarrow Cu$$

Write the balanced chemical equations of the following word equation:
Sodium chloride + manganese dioxide + sulphuric acid $$\rightarrow$$ sodium hydrogen sulphate + manganese sulphate + water + chlorine

The given word equation can be written as:

$$NaCl + MnO_2 + H_2SO_4 \rightarrow NaHSO_4 + MnSO_4 + H_2O + Cl_2$$

This equation is not balanced, so we will balance it step by step

Step 1: There is only one Cl at the left side but 2 on right side

Place 2 before NaCl to balance Cl atoms

Step 2: Now we have 2 Na at the left and 1 at the right

To balance Na atoms place 2 before $$NaHSO_4$$

Step 3: Now balance $$SO_4$$ which is 3 on the right side and 1 on the left side. To balance this place 3 before $$H_2SO_4$$ on left side

Step 4: Balance the hydrogens now by placing 2 before $$H_2O$$.

Now the equation is balanced

$$2NaCl + MnO_2 + 3H_2SO_4 \rightarrow 2NaHSO_4 + MnSO_4 + 2H_2O + Cl_2$$

Write balanced equation and give your observations the following metals react:
Sodium with cold water

When Sodium reacts with cold water. Hydrogen gas is evolved with generation of heat.
$$2Na+2H_2O \to 2NaOH +H_2$$

Write an equation to represent a chemical change.

A chemical reaction represents a true chemical change. In it, new substances are produced when two or more substances react. For example, the formation of magnesium oxide is an example of chemical change.

$$2Mg+O_2 \longrightarrow 2MgO$$

Give one example of decomposition reaction in which a solid and a gas are the two products obtained.

Decomposition of calcium carbonate gives calcium oxide (solid) and carbon dioxide (gas).

$$CaCO_3(s) \xrightarrow{heat} CaO(s)+CO_2(g)$$

Define corrosion, rusting and rancidity.

Corrosion: Metals when kept exposed, react with air moisture, acids, and other gas present in the atmosphere and get corrode. This process is called corrosion.

Rusting: Iron metal when left exposed, reacts with moisture and air and gets coated with a reddish-brown powdery substance called rust. This process is called rusting.

Rancidity: Food containing fats and oil when exposed to air gets oxidized and gives a bad taste and smell to food. This process is called rancidity.

What is rancidity?

Rancidity is the oxidation of fats present in food products and is characterized by unpleasant odours and flavours due to the change in the chemical composition of fats.

Name the type of reaction in which two or more than two reactants form a single compound.

A combination reaction is a reaction in which two or more substances combine to form a single compound.

For example, iron and sulphur combine to form iron sulphide.

$$Fe(s) + S(s) \xrightarrow{\Delta} FeS(s)$$

Define a chemical equation.

The symbolic representation of an actual chemical reaction is called a chemical equation.

Define chemical reaction and write its characteristics .

When one or more substance undergoes a complete change to form one or more substance is called a chemical reaction.

It is characterized by one or more characters like the change in state, change in color, the evolution of gas, change in temperature, the formation of a precipitate, etc.

Name the type of reaction for the following:
Vegetable matter changing into compost.

Vegetable matter is changed into compost by microorganisms using decomposition reactions. The complex organic material of vegetable matter is broken down into simpler molecules during this process.

Name the chemical reaction responsible for rancidification of food.

Rancidification is the process of complete or incomplete oxidation of fats and oils when exposed to air, light, or moisture or by bacterial action, resulting in unpleasant taste and odour. Hence, the oxidation reaction is responsible for the rancidification of food.

Write the steps of writing a chemical equation. What are the characteristics of a chemical equation?

Following are different steps of writing a chemical equation:

1) Identify the type of reactant and product. Write a word equation

hydrogen gas + oxygen gas = water

2) Write the chemical formula for each of the reactants and products

$$H_2 +O_2 \longrightarrow H_2O$$

3) Count the number of each type of atom in reactants and products

$$H_2 +O_2 \longrightarrow H_2O$$

LHS RHS

H=2; H =2

O=2; O=1

4) Balance the equation

Compare the number of each type of atom on both sides (reactants and products) and try to balance the reaction by placing appropriate coefficients in front of the reactants and products.

$$2H_2 +O_2 \longrightarrow 2H_2O$$

5) Check whether the reaction balanced or not (Atoms on LHS= Atoms on RHS)

$$2H_2 +O_2 \longrightarrow 2H_2O$$

LHS RHS

H=4; H =4

O=2; O=2

Characteristics of Chemical Equation:

The chemical equation gives brief information about chemical reactions. They are as follows:

1) Complete information about reactants and products, e.g. number of molecules, mass, etc.

2) Physical states of substances.

3) Necessary conditions for chemical equation, e.g temperature, pressure, catalyst, etc.

4) Equation also shows if the reaction is exothermic or endothermic.

5) Equation also shows the reversibility of chemical reactions.

Suggest some measures to avoid rancidity of oils.

Rancidity of oils can be avoided by

1. keeping in air tight container.

2. using antioxidants such as nitrogen.

3. by doing hydrogenation of oils.

Name the type of reaction for the following:
Burning of natural gas.

$$Exothermic \ Reaction$$

The burning of natural gas leads to the evolution of heat hence it is an example of an exothermic reaction.

As natural gas contains hydrocarbons that undergoes oxidation to form $$CO_2$$ and $$H_2O$$

State any two observations in an activity that may suggest that a chemical reaction has taken place. Give examples to support your answer.

The following observations in an activity may suggest that a chemical reaction has taken place:

$$\bullet$$ Change in state

$$\bullet$$ Change in colour

$$\bullet$$ Evolution of a gas

$$\bullet$$ Change in temperature

(i) Calcium oxide reacts vigorously with water to produce calcium hydroxide. During this process, a large amount of heat is also evolved, which increases the temperature of the system. This confirms that a chemical reaction has taken place.

$$CaO(s) +H_2O(l)\rightarrow Ca(OH)_2(aq)$$

ii) Also, when calcium carbonate is heated, it decomposes to form calcium oxide and carbon dioxide.

Here, evolution of the gas (carbon dioxide) confirms that a chemical reaction has taken place.

$$CaCO_3\rightarrow CaO +CO_2$$

Identify the substances that are oxidized and the substances that are reduced in the following reactions.
$$ 4Na (s) + O_2 (g) \rightarrow 2Na_2O (s) $$

In this given reaction, $$ 4Na (s) + O_2 (g) \rightarrow 2Na_2O (s) $$

$$\bullet$$ Sodium (Na) is gaining oxygen to form $$Na_2O$$. Hence, sodium (Na) is being oxidized and oxygen is getting reduced (oxygen is a reduced substance).

$$2Na\rightarrow Na_2O$$

$$\text{Additional information}$$

$$\bullet$$ The substance that gains oxygen is being oxidised and is the oxidised substance.

$$\bullet$$ The substance that loses oxygen is being reduced and is the reduced substance.

Identify the substances that are oxidized and the substances that are reduced in the following reactions.
$$ CuO(s) + H_2(g) \rightarrow Cu(s) + H_2O (l) $$

In this given reaction, $$ CuO(s) + H_2(g) \rightarrow Cu(s) + H_2O (l) $$

$$\bullet$$ Copper oxide $$(CuO)$$ is losing oxygen to form copper $$Cu$$. Hence, copper oxide $$(CuO)$$ is being reduced.

$$CuO\rightarrow Cu$$

$$\bullet$$ Hydrogen $$(H)$$ is gaining oxygen to form water $$(H_2O)$$. Hence, hydrogen is getting oxidized.

$$H\rightarrow H_2O$$

$$\text{Additional information}$$

$$\bullet$$ The substance that gains oxygen is being oxidised and is the oxidised substance.

$$\bullet$$ The substance that loses oxygen is being reduced and is the reduced substance.

Discuss oxidation and reduction in the chemical process given below:

$$H_2 + CuO \rightarrow Cu + H_2O$$

In the given reaction, oxygen gets separated from $$CuO$$ and is added to $$H_2$$.

So, $$CuO$$ undergoes reduction to form $$Cu$$ and $$H_2$$ undergoes oxidation to form $$H_2O$$.

Some incomplete equations are given below:
$$MgSO_4 +BaCl_2 \to ..... +MgCl_2$$
Complete the equation.

Complete Equation: $$MgSO_4 +BaCl_2 \to BaSO_4 +MgCl_2$$

Mention the formula, name and physical state of the products of following reactions :
$$AgNO_{3} (aq) + NaCl (aq) \rightarrow AgCl (s) + NaNO_{3} (aq)$$

$$AgNO_{3} (aq) + NaCl (aq) \rightarrow AgCl (s) + NaNO_{3} (aq)$$

$$AgCl$$ – Silver Chloride

$$NaNO_{3}$$ – Sodium Nitrate
Physical state of $$AgCl$$ is solid and of $$NaNO_3$$ is aqueous in nature.

Write a balanced chemical equation with state symbols for the following reactions.
(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble barium sulphate and the solution of sodium chloride.
(ii) Sodium hydroxide solution(in water) reacts with hydrochloric acid solution(in water) to produce sodium chloride solution and water.

(i)

The balanced chemical equation of the reaction that occurs, when the solution of barium chloride$$(BaCl_2)$$ and sodium sulphate$$(Na_2SO_4)$$ in water to form insoluble barium sulphate$$(BaSO_4)$$ and the solution of sodium chloride$$(NaCl)$$ is as follows;

$$BaCl_{{2}{(aq)}} + Na_2SO_{{4}{(aq)}}\rightarrow BaSO_{{4}(s)} + 2NaCl_{(aq)}$$

(ii)

The balanced chemical equation of the reaction that occurs, when sodium hydroxide$$(NaOH)$$ solution (in water) reacts with hydrochloric acid$$(HCl)$$ solution (in water) to form sodium chloride$$(NaCl)$$ solution and water$$(H_2O)$$ is as follows:

$$NaOH_{(aq)} + HCl_{(aq)}\rightarrow NaCl_{(aq)} + H_2O_{(liq)}$$

Mention the formula, name and physical state of the products of following reactions :
$$Na_{2}SO_{4} (aq) + Ba(OH)_{2} (aq) \rightarrow$$

$$Na_{2}SO_{4} (aq) + Ba(OH)_{2} (aq) \rightarrow BaSO_{4} (s) + 2NaOH(aq)$$

Products

$$BaSO_{4}$$ – Barium sulphate (Solid)

$$NaOH$$ – Sodium hydroxide (Liquid)

Mention the formula, name and physical state of the product of following reactions :
$$CO_{2} (g) + H_{2}O (l) \rightarrow H_{2}CO_{3} (aq)$$

$$CO_{2} (g) + H_{2}O (l) \rightarrow H_{2}CO_{3} (aq)$$

$$H_{2}CO_{3}$$– Carbonic acid
Physical state of carbonic acid is aqueous means it is dissolved in water.

What is meant by reduction?

A reduction reaction is a chemical reaction in which oxygen is removed or hydrogen is added to an element, molecule, or compound.
$$Fe_{2}O_{3}+2Al\rightarrow 2Fe+Al_{2}O_{3}$$
in this reaction $$Fe_{2}O_{3}$$ lose oxygen so it will reduced.

Name the substance oxidised and reduced and also identify oxidising agents and reducing agents in the
following reactions :
$$1)Fe_{2}O_{3} + 3CO \rightarrow 2Fe + 3CO_{2} $$
$$2)MnO_{2} + 4Al \rightarrow 3Mn + 2Al_{2}O_{3} $$
$$3)H_{2}S + SO_{2} \rightarrow S+ H_{2}O $$

(i)

Given reaction, $$Fe_{2}O_{3} + 3CO \rightarrow 2Fe + 3CO_{2} $$

$$\text{Part 1: Reduced substance or oxidising agent}$$

$$\bullet$$ Iron oxide $$(Fe_2O_3)$$ is losing oxygen to form iron $$Fe$$. Hence, Iron oxide $$(Fe_2O_3)$$ is being reduced.

$$Fe_2O_3\rightarrow Fe$$

$$\bullet$$ In the above reaction, iron oxide $$(Fe_2O_3)$$ is being reduced by losing oxygen atoms and thus here iron oxide $$(Fe_2O_3)$$ acts as an oxidising agent as it undergoes reduction.

$$\text{Part 2: Oxidised substance or reducing agent}$$

$$\bullet$$ Carbon monoxide $$(CO)$$ is gaining oxygen to form carbon dioxide $$(CO_2)$$. Hence, Carbon monoxide $$(CO)$$ is getting oxidized.

$$CO\rightarrow CO_2$$

$$\bullet$$ In the above reaction, carbon atom in carbon monoxide $$(CO)$$ is being oxidized into carbon dioxide $$(CO_2)$$ by gaining oxygen atom. Thus $$CO$$ is a reducing agent as it undergoes oxidation by gaining oxygen atoms.

(ii)

Given reaction, $$MnO_{2} + 4Al \rightarrow 3Mn + 2Al_{2}O_{3} $$

$$\text{Part 1: Reduced substance or oxidising agent}$$

$$\bullet$$ Manganese oxide $$(MnO_2)$$ is losing oxygen to form manganese $$Mn$$. Hence, manganese oxide $$(MnO_2)$$ is being reduced.

$$MnO_2\rightarrow Mn$$

$$\bullet$$ In the above reaction, manganese oxide $$(MnO_2)$$ is being reduced by losing oxygen atoms and thus here manganese oxide$$(MnO_2)$$ acts as an oxidising agent as it undergoes reduction.

$$\text{Part 2: Oxidised substance or reducing agent}$$

$$\bullet$$ Aluminium $$(Al)$$ is gaining oxygen to form aluminium oxide $$(Al_2O_3)$$. Hence, aluminium $$(Al)$$ is getting oxidized.

$$Al\rightarrow Al_2O_3$$

$$\bullet$$ In the above reaction, aluminium $$(Al)$$ is being oxidized into aluminium oxide $$(Al_2O_3)$$ by gaining oxygen atom. Thus aluminium $$Al$$ is a reducing agent as it undergoes oxidation by gaining oxygen atoms.

(iii)

Given reaction, $$H_{2}S + SO_{2} \rightarrow S+ H_{2}O $$

$$\text{Part 1: Reduced substance or oxidising agent}$$

$$\bullet$$ Sulphur dioxide $$(SO_2)$$ is losing oxygen to form sulphur $$S$$. Hence, sulphur dioxide $$(SO_2)$$ is being reduced.

$$SO_2\rightarrow S$$

$$\bullet$$ In the above reaction, sulphur dioxide is being reduced by losing oxygen atoms and thus here sulphur dioxide acts as an oxidising agent as it undergoes reduction.

$$\text{Part 2: Oxidised substance or reducing agent}$$

$$\bullet$$ Hydrogen sulphide $$(H_2S)$$ is gaining oxygen to form water $$(H_2O)$$. Hence, hydrogen sulphide $$(H_2S)$$ is getting oxidized.

$$H_2S\rightarrow H_2O$$

$$\bullet$$ In the above reaction, hydrogen sulphide $$(H_2S)$$ is being oxidized into water by gaining oxygen atom. Thus hydrogen sulphide $$(H_2S)$$ is a reducing agent as it undergoes oxidation by gaining oxygen atoms.

Explain different types of decomposition reactions.

Based on the cause of reaction, decomposition reactions are of following type:

$$\bullet$$ Electrical Decomposition: When an electric current is passed through molten or aqueous form of a substance and the substance dissociates into two or more products.

$$\bullet$$ Thermal Decomposition: When decomposition reaction takes place due to heat, it is called thermal decomposition.

$$\bullet$$ Photo Decomposition: When decomposition reaction takes place due to light, it is called photo decomposition.

A compound 'A' is used in the manufacture of cement. When dissolved in water, it evolves a large amount of heat and forms compound 'B'.
i) Identify A and B.
ii) Write chemical equation for the reaction of A with water.
iii) List two types of reaction in which this reaction may be classified.

(i)

Compound 'A' is calcium oxide $$(CaO)$$ and 'B' is calcium hydroxide $$(Ca(OH)_2)$$.

$$\bullet$$ Calcium oxide is used in the manufacture of cement.

(ii) The chemical equation involved for the reaction of A (calcium oxide) with water is as follows:

$$CaO + H_2O\rightarrow Ca(OH)_2 + heat$$

$$\bullet$$ Calcium hydroxide is formed along with the production of heat when calcium oxide reacts with water.

$$\bullet$$ Calcium hydroxide is also known as slaked lime.

$$\bullet$$ It is used as an ingredient in whitewash, mortar and plaster.

(iii) The two types of reaction involved when calcium oxide reacts with water are combination reaction and exothermic reaction.

$$CaO + H_2O\rightarrow Ca(OH)_2 + heat$$

$$\bullet$$ A combination reaction is a reaction in which two or more reactants combine to form a single product.

$$\bullet$$ A reaction in which energy is released in the form of light or heat is known as an exothermic reaction.

What is meant by skeletal type chemical equation? How can it be represented? Using the equation for electrolytic decomposition of water, differentiate between a skeletal chemical equation and a balanced chemical equation.

$$\text{Part 1: Skeletal type chemical equation}$$

Skeletal equations are those in which formulas are used to show which chemicals are involved in a chemical reaction.

$$\bullet$$ Skeletal equation does not follow the law of conservation of mass and only represents chemical formulas.

$$\text{Part 2: Representation of skeletal type chemical equation}$$

$$\bullet$$ It represents an unbalanced chemical reaction.

$$\bullet$$ For example, the skeletal chemical equation is as follows:

$$H_2O\rightarrow H_2 + O_2$$

$$\text{Part 3: Difference between skeletal chemical equation and balanced chemical equation}$$

$$\text{Skeletal chemical equation}$$	$$\text{Balanced chemical equation}$$
(i) Skeletal equation does not follow the law of conservation of mass and only represents chemical formulas.	(ii) Chemical formulas are represented by a balanced chemical equation, which follows the law of conservation of mass (which states that the atoms on the reactant and product sides are the same).
(ii) The representation of the skeletal chemical equation for the electrolytic decomposition of water is as follows: $$H_2O\rightarrow H_2 + O_2$$	(ii) The representation of the balanced chemical equation for the electrolytic decomposition of water is as follows: $$2H_2O\rightarrow 2H_2 + O_2$$

$$\text{Additional Information}$$

$$\bullet$$ Decomposition reaction is a reaction in which a single reactant breaks down into two or more products.

Divide the following redox reactions into oxidation and reduction half reactions.
$$Zn + Pb^{2+} \longrightarrow Zn^{2+} + Pb$$

The given reaction is as follows:

$$Zn + Pb^{2+} \rightarrow Zn^{2+} + Pb$$

The loss of electrons is considered oxidation and It occurs at the anode.

The oxidation half-reaction is as follows:

$$Zn\rightarrow Zn^{2+}+2e^{-}$$

In the reaction, Zn loses 2 electrons and gets oxidized at the anode.

The gain of electrons is considered as reduction. It occurs at the cathode.

The reduction half-reaction is as follows:
$$Pb^{2+}+2e^{-}\rightarrow Pb$$

In the reaction, Pb accepts 2 electrons and gets reduced at the cathode.

How is sodium hydroxide manufactured in industries ? Name the process. In this process a gas X is formed as byproduct. This gas reacts with lime water to give a compound Y, which is used as a bleaching agent in the chemical industry. Identify X and Y and write the chemical equation of the reactions involved.

$$\bullet$$ Solution of Sodium chloride $$(NaCl)$$ is used for manufacture of sodium hydroxide $$(NaOH)$$ by chlor-alkali process. It is an electrolysis process.

$$\bullet$$ In this process chlorine and hydrogen gas are formed as byproducts along with sodium hydroxide.

$$2NaCl(aq) + 2H_2O(l) \rightarrow 2NaOH + Cl_2(g) + H_2(g)$$

$$\bullet$$ Chlorine gas gives bleaching powder when reacts with lime water and used as bleaching agent in chemical industries.

$$Ca(OH)_2 + Cl_2 \rightarrow CaOCl_2 + H_2O$$

Therefore,

$$\bullet$$ The gas X is chlorine gas.

$$\bullet$$ Compound Y is calcium oxychloride ($$CaOCl_2$$) which is commonly known as bleaching powder and used as bleaching agent in chemical industries.

Rearrange the table with correct pairing.

Reactants Products Types of Reactions
$$Fe + S$$ $$NaCl + H_2O$$ Oxidation
$$CuSO_4 + Zn$$ $$2CuO$$ Neutralization
$$2Cu + O_2$$ $$ZnSO_4 + Cu$$ Displacement
$$HCl + NaOH$$ $$FeS$$ Combination

Rearranging the table with the correct pairing:

Reactants

Products

Types of Reactions

$$Fe + S$$

$$FeS$$

Combination

$$CuSO_4 + Zn$$

$$ZnSO_4 + Cu$$

Displacement

$$2Cu + O_2$$

$$2CuO$$

Oxidation

$$HCl + NaOH$$

$$NaCl + H_2O$$

Neutralization

Combination reaction is one in which a single product is formed from two or more reactants.
Displacement reaction is one in which a more reactive element displaces a less reactive element from a compound.
Oxidation reaction is one in which a substance gains oxygen.
Neutralization reaction is one in which an acid and a base react to form salt and water.

Give reason:
White-colored $$AgCl$$ turns grey when kept in sunlight.

White silver chloride turns grey in sunlight due to the decomposition of silver chloride into silver and chlorine by light.

The reaction that takes place is:

$$2AgCl \xrightarrow{sunlight} 2Ag + Cl_2$$

Write the balanced chemical equation for the following and identify the type of reaction in each case:

(a) Potassium bromide(aq) + Barium iodide(aq) $$\rightarrow$$ Potassium iodide(aq) + Barium bromide(s)

(b) Zinc carbonate(s) $$\rightarrow$$ Zinc oxide(s) + Carbon dioxide(g)

(c) Hydrogen(g) + Chlorine(g) $$\rightarrow$$ Hydrogen chloride(g)

(d) Magnesium(s) + Hydrochloric acid(aq) $$\rightarrow$$ Magnesium chloride(aq) + Hydrogen(g)

(a) Potassium bromide(aq) + Barium iodide(aq) $$\rightarrow$$ Potassium iodide(aq) + Barium bromide(s)

$$2KBr_{(aq)} + {BaI_2}_{(aq)} \rightarrow 2KI_{(aq)} + {BaBr_2}_{(s)}$$

In this reaction, both the reactants exchange ions to form two new products. Hence, it is a double displacement reaction

(b) Zinc carbonate(s) $$\rightarrow$$ Zinc oxide(s) + Carbon dioxide(g)

$${ZnCO_3}_{(s)} \rightarrow ZnO_{(s)} + {CO_2}_{(g)} $$

In this reaction, a single substance yields two different products. Hence, it is a decomposition reaction.

$${H_2}_{(g)} + {Cl_2}_{(g)}\rightarrow 2HCl_{(g)} $$

In this reaction, two different reactants react with each other to form a single product. Hence, it is called a combination reaction.

(d) Magnesium(s) + Hydrochloric acid(aq) $$\rightarrow$$ Magnesium chloride(aq) + Hydrogen(g)

$$Mg _{(s)}+ 2HCl_{(aq)} \rightarrow {MgCl_2}_{(aq)} + {H_2}_{(g)} $$

In this reaction, more reactive Mg is replacing less reactive H. Hence, it is displacement reaction.

Translate the following statements into chemical equations and then balance them:

(a) Hydrogen gas combines with nitrogen to form ammonia.
(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

(a) Hydrogen gas combines with nitrogen to form ammonia.

$$H_2(g) + N_2(g) \rightarrow NH_3$$

The balanced equation for this reaction can be written as:

$$3H_2(g) + N_2(g) \rightarrow 2NH_3$$

(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.

$$H_2S(g) + O_2(g) \rightarrow H_2O + SO_2$$

The balanced equation for this reaction can be written as:

$$2H_2S(g) + 3O_2(g) \rightarrow 2H_2O + 2SO_2$$

$$BaCl_2 + Al_2(SO_4)_3 \rightarrow AlCl_3 + BaSO_4\downarrow$$

The balanced equation for this reaction can be written as:

$$3BaCl_2 + Al_2(SO_4)_3 \rightarrow 2AlCl_3 + 3BaSO_4\downarrow$$

(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.

$$K + H_2O \rightarrow KOH + H_2$$

The balanced equation for this reaction can be written as:

$$2K + 2H_2O \rightarrow 2KOH + H_2$$

Write the balanced chemical equations for the following reactions.

(a) Calcium hydroxide + Carbon dioxide $$\rightarrow$$ Calcium carbonate + Water

(b) Zinc + Silver nitrate $$\rightarrow$$ Zinc nitrate + Silver

(c) Aluminium + Copper chloride $$\rightarrow$$ Aluminium chloride + Copper

(d) Barium chloride + Potassium sulphate $$\rightarrow$$ Barium sulphate + Potassium chloride

(a) Calcium hydroxide + Carbon dioxide $$\rightarrow$$ Calcium carbonate + Water

$$Ca(OH)_2 + CO_2 \rightarrow CaCO_3 + H_2O$$

(b) Zinc + Silver nitrate $$\rightarrow$$ Zinc nitrate + Silver

$$Zn + 2AgNO_3 \rightarrow Zn(NO_3)_2 + 2Ag$$

$$2Al + 3CuCl_2 \rightarrow 2AlCl_3 + 3Cu$$

(d) Barium chloride + Potassium sulphate $$\rightarrow$$ Barium sulphate + Potassium chloride

$$BaCl_2 + K_2SO_4 \rightarrow BaSO_4 + 2KCl$$

What are the materials required for the experiment to show the chemical decomposition of water? Write the procedure of the experiment. Name the products which we get in this reaction.

Water can be decomposed using electrolysis.
Materials required are Pencils, electrolytic cells, batteries, distilled water and cardboard.
Procedure: 1. Fill the beaker or glass with warm water.

2. Put 2 sharp pencils as electrodes.

3. Connect each pencil to the battery.

4. Wrap the wire around the graphite of each pencil and connect the wires to the battery.

Products formed are Hydrogen gas and oxygen gas.

What happens when:
(a) dilute sulphuric acid is poured on a copper plate?
(b) iron nails are placed in copper sulphate solution?

Write word equations of the reactions involved.

a) $$Cu$$ do not react with dilute sulphuric acid as it comes behind hydrogen in the reactivity series. But with concentrated $$H_2SO_4$$ it reacts to form $$CuSO_4$$ and $$SO_2$$ is evolved.

$$Cu+2H_2SO_4 \ (conc) \rightarrow CuSO_4+SO_2+2H_2O$$

b) Since $$Fe$$ is more reactive than $$Cu$$. It will displace $$Cu$$ from $$CuSO_4$$ and form $$FeSO_4$$. A color change of blue to light green will occur.

$$Fe+CuSO_4 \rightarrow FeSO_4+Cu$$

Four metals $$A$$, $$B$$, $$C$$ and $$D$$ are in turn added to the following solutions one by one. The observations made are tabulated below.
Metal Iron (II) sulphate Copper (II) sulphate Zinc sulphate Silver nitrate
A No reaction Displacement - -
B Displacement - No reaction -
C No reaction No reaction No reaction Displacement
D No reaction No reaction No reaction No reaction
Answer the following based on the above information :
(i) Which is the most reactive metal? Why?
(ii) What would be observed, if '$$B$$' is added to a solution of Copper (II) sulphate and why?
(iii) Arrange the metals $$A$$, $$B$$, $$C$$ and $$D$$ in order of increasing reactivity.
(iv) Which one among $$A$$, $$B$$, $$C$$ and $$D$$ metals can be used to make containers that can be used to store any of the above solutions safely?

(i) B is the most reactive metal as it has displaced the most reactive metal amongst the solutions i.e Fe of $$FeSO_4$$.

(ii) If B is added to $$CuSO_4$$ solution than it will displace Cu because Fe is more reactive than Cu so the metal which can displace Fe can also displace Cu.

(iii) D < C < A < B.

(iv) Metal D can be used to make containers to store the solutions because it is the least reactive metal of all.

Do you expect different products in solution when aluminium (III) chloride and potassium chloride treated separately with (i) normal water (ii) acidified water, and (iii) alkaline water? Write equations wherever necessary.

KCl is a salt of strong acid HCl and strong base KOH. Such salts are neutral in nature and do not undergo hydrolysis. In neutral water, acidic water, and alkaline water, KCl dissociates as
$$\displaystyle KCl \xrightarrow {Water} K^+ + Cl^-$$

$$\displaystyle AlCl_3 $$ is a salt of strong acid HCl and weak base $$\displaystyle Al(OH)_3 $$.
In normal water, it is hydrolyzed.
$$\displaystyle AlCl_3+3H_2O \rightarrow Al(OH)_3 + 3H^++3Cl^- $$

In acidic water, $$\displaystyle H^+ $$ ions react with $$\displaystyle Al(OH)_3 $$ (obtained from the hydrolysis of $$AlCl_3$$) forming water and $$\displaystyle Al^{3+} $$ ions. Hence it exists as $$\displaystyle Al^{3+}+Cl^- $$
$$\displaystyle AlCl_3 \xrightarrow [water]{acidified} Al^{+}+3Cl^- $$
In alkaline water, the $$Al(OH)_3 $$ obtained from hydrolysis of $$AlCl_3$$ reacts with hydroxide ions of alkali. The reaction is
$$\displaystyle Al(OH)_3 + OH^- \rightarrow [Al(OH)_4]^- $$

Write the word equations and the balanced equations for the reaction taking place when:
Dilute sulphuric acid reacts with zinc granules.

The word equation is:

Sulphuric acid (dil) + Zinc $$\rightarrow$$ Zinc sulphate + Hydrogen

$$H_2SO_4(dil) + Zn \rightarrow ZnSO_4+H_2$$

Ammonium chloride, a sublimable solid undergoes _____ (synthesis/dissociation) on heating.

When ammonium chloride is heated it undergoes dissociation to form a product such as $$N{ H }_{ 3 }$$ and $${ H }Cl$$. The ammonium chloride undergoes sublimation when it is heated, the substance changes from solid to gas. The gas contains molecules such as ammonia and hydrogen chloride.

Complete and balance the following reaction:
$$CaCN_2 +H_2O (steam) \to CaCO_3 +.....$$

Those reactions in which two compounds react by an exchange of ions to form two new compounds are called double displacement reactions;
$$CaCN_{2}+3H_{2}O_(aq)\rightarrow CaCO_{3}+2NH_{3}$$
this is a type of double displacement reaction

Give one example each of a chemical reaction characterised by

Evolution of a gas.
Change in colour.
Formation of a precipitate.
Change in temperature.
Change in state.

1. Evolution of gas:

The chemical reaction between zinc and dilute sulphuric acid is characterized by the evolution of hydrogen gas.

$$Zn(s) + H_2SO_4(aq) \rightarrow ZnSO_4(aq)+H_2(g)$$

2. Change in colour:

The reaction between lead nitrate solution and potassium iodide solution.

$$Pb(NO_3)_2(aq) +2KI \rightarrow PbI_2(s) + 2KNO_3(aq)$$

In this reaction colour changes from colourless to yellow.

3. Formation of precipitate:

The action of barium chloride on sodium sulphate.

$$BaCl_2(aq) +Na_2SO_4(aq) \rightarrow BaSO_4(s) + 2NaCl(aq)$$

4. Change in temperature:

The action of dilute sulphuric acid on zinc.

$$Zn(s) +H_2SO_4(aq) \rightarrow ZnSO_4(s) + H_2(g)$$

In this reaction, heat is evolved.

5. Change in the state:

When wax is burnt in the form of the wax candle, then water and carbon dioxide are formed. Wax is solid, water is a liquid whereas carbon dioxide is a gas.

Give two examples of a reaction which is both endothermic and decomposition in nature.

These are the reaction which is both endothermic and decomposition in nature.

$$CaCO_3(s) \xrightarrow []{heat}CaO(s)+CO_2(g)$$

$$ZnCO_3(s) \xrightarrow []{heat}ZnO(s)+CO_2(g)$$

Give an example of a reaction where heat is involved.

$$2Pb(NO_3)_2\xrightarrow\Delta{ }2PbO+4NO_2+O_2$$

This is a decomposition reaction that occurs in presence of heat.

Answer the following questions:

a) Explain the term "rancidity". What damage is caused by rancidity?
b) What type of chemical reaction is responsible for causing rancidity?
c) State and explain the various methods for preventing or retarding the rancidity of food.

a) The condition produced by aerial oxidation of fats and oils in foods marked by unpleasant smell and taste is called rancidity. It spoils the food materials prepared in fats and oils which have been kept for a considerable time and makes them unfit for eating.

b) Oxidation is responsible for causing rancidity.

c) The various methods for preventing or retarding rancidity of food are:

1) Rancidity can be prevented by adding anti-oxidants to foods containing fats and oils.

2) It can be prevented by packaging fat and oil-containing foods in nitrogen gas.

3) It can be retarded by keeping food in a refrigerator.

4) It can be prevented by storing food in air-tight containers.

5) Storing foods away from light can also prevent rancidity.

Match the following
Column I Column II
a) $$Zn_{(s)} + H_2SO_{4(aq)} \to ZnSO_{4(aq)} + H_{2(g)}$$
i) Photochemical decomposition
b) $$2AgCl(s) \xrightarrow{sunlight} 2Ag(s) + Cl_2(g)$$ ii) Thermal decomposition
c) $$2KCl \xrightarrow{electricity} 2K + Cl_2$$ iii) Displacement reaction
d) $$2Hg_{(s)} \xrightarrow{\Delta} 2Hg_{(s)} + O_2$$ iv) Electrolytic decomposition

a) $$Zn_{(s)} + H_2SO_{4(aq)} \to ZnSO_{4(aq)} + H_{2(g)}$$ $$\Rightarrow$$ iii) Displacement reaction

b) $$2AgCl(s) \xrightarrow{sunlight} 2Ag(s) + Cl2(g)$$ $$\Rightarrow$$ i) Photochemical decomposition

c) $$2KCl \xrightarrow{electricity} 2K + Cl_2$$ $$\Rightarrow$$ iv) Electrolytic decomposition

d) $$2Hg(s) \xrightarrow{\Delta} 2Hgs + O_2$$ $$\Rightarrow$$ ii) Thermal decomposition

Name the different forms of energy required for breaking down the reactants in decomposition reaction.

During the decomposition of a reactant, the reactant needs the energy to break the reactants to produce products.

The energy can be in the form of light or heat or electricity energy.

What is rancidity? What is the general name of chemical which are added to fat and oil containing food so as to prevent the rancidity?

Oil and fat-containing food when left exposed to air reacts with oxygen oxidized and become rancid, this process is called rancidity. In this process their smell and taste changes.

The general name of the chemicals that are added to prevent this oxidation are called as antioxidants. For example, nitrogen gas is an antioxidant.

Metal	Iron (II) sulphate	Copper (II) sulphate	Zinc sulphate	Silver nitrate
A	No reaction	Displacement	-	-
B	Displacement	-	No reaction	-
C	No reaction	No reaction	No reaction	Displacement
D	No reaction	No reaction	No reaction	No reaction

	Column I		Column II
a)	$$Zn_{(s)} + H_2SO_{4(aq)} \to ZnSO_{4(aq)} + H_{2(g)}$$	i)	Photochemical decomposition
b)	$$2AgCl(s) \xrightarrow{sunlight} 2Ag(s) + Cl_2(g)$$	ii)	Thermal decomposition
c)	$$2KCl \xrightarrow{electricity} 2K + Cl_2$$	iii)	Displacement reaction
d)	$$2Hg_{(s)} \xrightarrow{\Delta} 2Hg_{(s)} + O_2$$	iv)	Electrolytic decomposition

Chemical Reactions And Equations - Class 10 Chemistry - Extra Questions

Complete the statement by filling the gaps using the appropriate terms.An ...... is drawn in between the reactants and products while writing the equation for a chemical reaction.

Give the reason for the following:Respiration is an exothermic reaction.

Mention the types of chemical reactions.

A decomposition reaction taking place due to the passage of electric current is called ___________.

The arrow mark between the products and reactants of a chemical equation shows __________ of the reaction.

What is a combination reaction? Write combination reaction of quick lime with water.

Write balanced chemical equations for the following word equation:Nitrogen + Oxygen $$\rightarrow $$ Nitric Oxide

Write a balanced chemical equation for each of the following:Action of dilute hydrochloric acid on Iron

Name the substance oxidized and reduced in the given reaction$$Cl_2 + H_2S\rightarrow 2HCl + S$$

Write a balanced chemical equation for each of the following:Action of heat on calcium bicarbonate

Write equations for the following reactions: (i) Aluminium oxide and Sodium hydroxide. (ii) Zinc and dilute sulphuric acid.

A student took a solution of copper sulphate in a beaker and put a clean iron nail into it and left it for about an hour.a) What changes do you expect?b) Are these changes chemical in nature?c) Write a word equation for the chemical change, if any.

Write the essential condition for the following reaction to take place: $$2AgBr\rightarrow 2Ag + Br_2$$Write an application of this reaction.

An iron salt A reacts with NaOH to form a green precipitate. Another iron salt B reacts with NaOH to form a brown precipitate. Identify the iron salts, A and B along with their colours and write the reactions involved.

Activity:Take lead nitrate solution in a test tube.Add potassium iodide solution to this.What do you observe ?

What is a redox reaction? Identify the substances oxidized and the substances reduced in the following reactions.1) $$2PbO + C\rightarrow 2Pb+CO_2$$2) $$MnO_2 + 4HCl\rightarrow MnCl_2 + 2H_2O + Cl_2$$

A student has mixed the solutions of lead $$ (II) $$ nitrate and potassium iodide.(i) What was the colour of the precipitate formed? Can you name the compound?(ii) Write the balanced chemical equation for this reaction.(iii) What type of reaction is it?

Classify each of the following reactions as a combination, decomposition, displacement, or double displacement:$$CaO+H_{2}O\rightarrow Ca\left(OH\right)_{2}$$

$$\text{Name the organic compound prepared by each of the following reactions}:$$ $$CH_{3}COONa + NaOH \xrightarrow[\Delta]{CaO}$$

When ammonium chloride is dissolved in water in a test tube, the test tube becomes cold why?

Classify each of the following reactions as a combination, decomposition, displacement, or double displacement:$$BaCl_{2}+Na_{2}SO_{4}\rightarrow BaSO_{4}+2NaCl$$

2 g of ferrous sulphate crystals are heated in a dry boiling tube. Name the type of chemical reaction taking place.

Classify each of the following reactions as a combination, decomposition, displacement, or double displacement:$$2KClO_{3}\rightarrow 2KCl+3O_{2}$$

Name the gas that evolved when ethanoic acid is added to sodium carbonate. How would you prove the presence of this gas?

2 g of ferrous sulphate crystals are heated in a dry boiling tube.Is this also a double displacement reaction ?

Why can copper displace silver from silver nitrate and silver cannot displace copper from copper sulphate solution? Give example.

Identify the following reactions as i) combination ii) decomposition iii) displacement reactions and doubledisplacement reaction$$CaCO_{3}(s) \rightarrow CaO(s) + CO_{2}(g)$$

Identify the following reactions as i) combination ii) decomposition iii) displacement reactions and doubledisplacement reaction$$ Fe_{2}O_{3} + Al \rightarrow Al_{2}O_{3} + 2Fe $$

Identify the following reactions as i) combination ii) decomposition iii) displacement reactions and double displacement reaction$$Pb(s) + CuCl_{2} \rightarrow PbCl_{2} + Cu(s)$$

Identify the following reactions asi) combination ii) decomposition iii) displacement reactions and double displacement reaction$$NaCl + AgNO_{3} \rightarrow AgCl + NaNO_{3} $$

Name the brown coloured gas evolved when lead nitrate crystal are heated in dry test-tube.

$$Zn + H_{2}SO_{4} \rightarrow ZnSO_{4} + H_{2}$$Write the ionic equation for the reaction.

Identify the following reaction as i) combination ii) decomposition iii) displacement reactions and double displacement reaction.$$ZnCO_{3}(s) \rightarrow ZnO(s) + CO_{2}(g)$$

Identify the following reactions as i) combination ii) decomposition iii) displacement reactions and doubledisplacement reaction$$3H_{2}(g)+ N_{2}(s) \rightarrow 2NH_{3} $$

Identify the following reactions as i) combination ii) decomposition iii) displacement reactions and double displacement reaction$$H_{2}(g)+ Cl_{2} \rightarrow 2HCl$$

Following observations are recorded during a number of experiments on the substance P. When the substance P is heated, a reddish brown gas is evolved along with a gas which relights glowing wooden splint. A yellow residue is left in the test tube.Name the gas which relights the glowing splint.

Mention the physical states of the reactants and products of the following chemical reactions and balance theequation.$$NH_{3} + Cl_{2} \rightarrow N_{2} + NH_{4}Cl$$

Following observations are recorded during a number of experiments on the substance P. When the substance P is heated, a reddish brown gas is evolved along with a gas which relights glowing wooden splint. A yellow residue is left in the test tube.Name the reddish brown gas,

What is decomposition reaction? Explain it with suitable example.

Burning magnesium ribbon in the air to form magnesium oxide is an example of _______ (combination/decomposition) reaction.

Digestion of food is an example of ______ (physical/chemical) change.

Respiration is an example of ____________ (physical/chemical) change.

Heat is released in _______ (endothermic/exothermic) reactions.

________ reactions called the opposite of combination reactions.

In a solution of silver nitrate, a copper plate was dipped. After some time, silver from the solution was deposited on the copper plate. Which metal is more reactive, copper or silver?

What do you see when a magnesium ribbon is burnt? Is magnesium oxidized or reduced in this reaction?

What is the difference between displacement and double displacement reactions? Write equations for these reactions?

Which reaction is this?$$2NaHCO_{3}\xrightarrow {heat} Na_{2}CO_{3} + H_{2}O + CO_{2}$$

What causes rancidity? Name an antioxidant which prevents rancidity.

Write one difference between displacement and double displacement reactions.

What happens when:i) $$CuS{ O }_{ 4 }\left( aq \right) +Fe\left( s \right) \rightarrow $$?ii) $$Zn\left( s \right) +{ H }_{ 2 }S{ O }_{ 4 }\left( l \right) \rightarrow $$?iii) $$Na\left( s \right) +{ O }_{ 2 }\left( g \right) \rightarrow $$?

Explain rancidity.

Give the name of the gas that evolved when sodium hydroxide reacts with zinc metal. Write the equation also.

Write the balanced chemical equation when zinc reacts with dilute nitric acid.

(a) What is a displacement reaction?(b) Identify A in the following reactions.(i) $$Zn+CuSO_4\rightarrow A+Cu$$(ii) $$Na_2SO_4+BaCl_2\rightarrow A+2NaCl$$.

Choose the correct answer from the four alternatives given in the brackets:$$Zn+2HCl\longrightarrow Zn{ Cl }_{ 2 }+{ H }_{ 2 }\uparrow $$The above reaction is an example of _______.(Combination reaction, Double displacement reaction, Displacement reaction, Decomposition reaction)

Explain an experiment with a chemical equation to establish that iron is more reactive than silver.

What type of chemical reaction takes place when:(a) lime stone is heated.(b) a magnesium ribbon is burnt in air.

Write the balanced chemical reaction for the following and identify the type of reaction in each case.(A) $$Magnesium_{(a)} + Iodine_{(g)} \rightarrow Magnesium\ iodide_{(s)}$$(B) $$Zinc_{(s)} + Hydrochloric\ acid_{(aq)} \rightarrow Zinc\ chloride_{(aq)} + Hydrogen_{(g)}$$

Divide the following redox reactions into oxidation and reduction half reactions.$$Zn + Cu^{2+} \rightarrow Zn^{2+} + Cu$$

What is observed when a solution of sodium sulphate is added to a solution of barium chloride taken in a test tube? Write equation for the chemical reaction involved and name the type of reaction in this case.

State the law which is followed in balancing a chemical equation.

Taking into consideration the relationship in the first pair, complete the second pair.$$2H_2+O_2\rightarrow 2H_2O :$$ Combination Reaction $$:$$ $$:$$ $$CaCO_3\rightarrow CaO+CO_2$$ $$:$$ ___________.

Give an example of a double displacement reaction.

Write a balance chemical equation of the following:$$FeSO_4(s) \xrightarrow{heat} Fe_2O_3(s) + SO_2(g) + SO_3(g)$$

Write balanced chemical equations for the following word equation:Zinc + Steam $$\rightarrow $$ Zinc oxide + Hydrogen

State an important use of decomposition reaction.

Potassium metal reacts with water to give potassium hydroxide and hydrogen gas. Write balanced chemical equation for this reaction.

Complete the following reactions and give name of the products.$$CuSO_{4}(aq)+Pb(s)\longrightarrow .......+.........$$

When silver nitrate solution is added to a solution of $$A$$, a white precipitate, insolube in nitric acid is formed.

Explain Balanced equation with examples.

(a) A white powder is added while baking breads and cakes to make them soft and fluffy. Write the name of the powder. Name the main ingredients. Explain the function of each ingredient. (b) Write the chemical reaction taking place when the powder is heated during baking.

Fill in the blanks:In some chemical reactions an insoluble ................... is formed when two solutions are mixed.

Write balanced chemical equations for the following word equation:Potassium chlorate $$\rightarrow $$ Potassium chloride + Oxygen

When ammonium chloride is mixed with barium hydroxide in a beaker, it becomes cold.

Write balanced chemical equations for the following word equation:Copper +Oxygen $$\rightarrow $$ Copper (II) oxide

How to balance a reaction?

Give an example of a double displacement reaction other than the reaction of barium chloride with sodium sulphate.

In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.

Complete the statement by filling the gaps using the appropriate terms.
An ...... is drawn in between the reactants and products while writing the equation for a chemical reaction.

Give the reason for the following:
Respiration is an exothermic reaction.

Write balanced chemical equations for the following word equation:
Nitrogen + Oxygen $$\rightarrow $$ Nitric Oxide

Write a balanced chemical equation for each of the following:
Action of dilute hydrochloric acid on Iron

Name the substance oxidized and reduced in the given reaction
$$Cl_2 + H_2S\rightarrow 2HCl + S$$

Write a balanced chemical equation for each of the following:
Action of heat on calcium bicarbonate

Write equations for the following reactions:
(i) Aluminium oxide and Sodium hydroxide.
(ii) Zinc and dilute sulphuric acid.

A student took a solution of copper sulphate in a beaker and put a clean iron nail into it and left it for about an hour.
a) What changes do you expect?
b) Are these changes chemical in nature?
c) Write a word equation for the chemical change, if any.

Write the essential condition for the following reaction to take place:
$$2AgBr\rightarrow 2Ag + Br_2$$
Write an application of this reaction.

Activity:
Take lead nitrate solution in a test tube.
Add potassium iodide solution to this.
What do you observe ?

What is a redox reaction? Identify the substances oxidized and the substances reduced in the following reactions.

1) $$2PbO + C\rightarrow 2Pb+CO_2$$
2) $$MnO_2 + 4HCl\rightarrow MnCl_2 + 2H_2O + Cl_2$$

A student has mixed the solutions of lead $$ (II) $$ nitrate and potassium iodide.
(i) What was the colour of the precipitate formed? Can you name the compound?
(ii) Write the balanced chemical equation for this reaction.
(iii) What type of reaction is it?

Classify each of the following reactions as a combination, decomposition, displacement, or double displacement:
$$CaO+H_{2}O\rightarrow Ca\left(OH\right)_{2}$$

$$\text{Name the organic compound prepared by each of the following reactions}:$$
$$CH_{3}COONa + NaOH \xrightarrow[\Delta]{CaO}$$

Classify each of the following reactions as a combination, decomposition, displacement, or double displacement:
$$BaCl_{2}+Na_{2}SO_{4}\rightarrow BaSO_{4}+2NaCl$$

Classify each of the following reactions as a combination, decomposition, displacement, or double displacement:
$$2KClO_{3}\rightarrow 2KCl+3O_{2}$$

Identify the following reactions as
i) combination ii) decomposition iii) displacement reactions and double
displacement reaction
$$CaCO_{3}(s) \rightarrow CaO(s) + CO_{2}(g)$$

Identify the following reactions as
i) combination ii) decomposition iii) displacement reactions and double
displacement reaction
$$ Fe_{2}O_{3} + Al \rightarrow Al_{2}O_{3} + 2Fe $$

Identify the following reactions as
i) combination ii) decomposition iii) displacement reactions and double displacement reaction
$$Pb(s) + CuCl_{2} \rightarrow PbCl_{2} + Cu(s)$$

Identify the following reactions as
i) combination ii) decomposition iii) displacement reactions and double displacement reaction
$$NaCl + AgNO_{3} \rightarrow AgCl + NaNO_{3} $$

$$Zn + H_{2}SO_{4} \rightarrow ZnSO_{4} + H_{2}$$
Write the ionic equation for the reaction.

Identify the following reaction as
i) combination ii) decomposition iii) displacement reactions and double displacement reaction.
$$ZnCO_{3}(s) \rightarrow ZnO(s) + CO_{2}(g)$$

Identify the following reactions as
i) combination ii) decomposition iii) displacement reactions and double
displacement reaction
$$3H_{2}(g)+ N_{2}(s) \rightarrow 2NH_{3} $$

Identify the following reactions as
i) combination ii) decomposition iii) displacement reactions and double displacement reaction
$$H_{2}(g)+ Cl_{2} \rightarrow 2HCl$$

Following observations are recorded during a number of experiments on the substance P. When the substance P is heated, a reddish brown gas is evolved along with a gas which relights glowing wooden splint. A yellow residue is left in the test tube.
Name the gas which relights the glowing splint.

Mention the physical states of the reactants and products of the following chemical reactions and balance the
equation.
$$NH_{3} + Cl_{2} \rightarrow N_{2} + NH_{4}Cl$$

Following observations are recorded during a number of experiments on the substance P. When the substance P is heated, a reddish brown gas is evolved along with a gas which relights glowing wooden splint. A yellow residue is left in the test tube.
Name the reddish brown gas,

Which reaction is this?
$$2NaHCO_{3}\xrightarrow {heat} Na_{2}CO_{3} + H_{2}O + CO_{2}$$

What happens when:
i) $$CuS{ O }_{ 4 }\left( aq \right) +Fe\left( s \right) \rightarrow $$?
ii) $$Zn\left( s \right) +{ H }_{ 2 }S{ O }_{ 4 }\left( l \right) \rightarrow $$?
iii) $$Na\left( s \right) +{ O }_{ 2 }\left( g \right) \rightarrow $$?

(a) What is a displacement reaction?
(b) Identify A in the following reactions.
(i) $$Zn+CuSO_4\rightarrow A+Cu$$
(ii) $$Na_2SO_4+BaCl_2\rightarrow A+2NaCl$$.

Choose the correct answer from the four alternatives given in the brackets:
$$Zn+2HCl\longrightarrow Zn{ Cl }_{ 2 }+{ H }_{ 2 }\uparrow $$
The above reaction is an example of _______.
(Combination reaction, Double displacement reaction, Displacement reaction, Decomposition reaction)

What type of chemical reaction takes place when:
(a) lime stone is heated.
(b) a magnesium ribbon is burnt in air.

Write the balanced chemical reaction for the following and identify the type of reaction in each case.
(A) $$Magnesium_{(a)} + Iodine_{(g)} \rightarrow Magnesium\ iodide_{(s)}$$
(B) $$Zinc_{(s)} + Hydrochloric\ acid_{(aq)} \rightarrow Zinc\ chloride_{(aq)} + Hydrogen_{(g)}$$

Divide the following redox reactions into oxidation and reduction half reactions.
$$Zn + Cu^{2+} \rightarrow Zn^{2+} + Cu$$

Taking into consideration the relationship in the first pair, complete the second pair.
$$2H_2+O_2\rightarrow 2H_2O :$$ Combination Reaction $$:$$ $$:$$ $$CaCO_3\rightarrow CaO+CO_2$$ $$:$$ ___________.

Write a balance chemical equation of the following:
$$FeSO_4(s) \xrightarrow{heat} Fe_2O_3(s) + SO_2(g) + SO_3(g)$$

Write balanced chemical equations for the following word equation:
Zinc + Steam $$\rightarrow $$ Zinc oxide + Hydrogen

Complete the following reactions and give name of the products.
$$CuSO_{4}(aq)+Pb(s)\longrightarrow .......+.........$$

(a) A white powder is added while baking breads and cakes to make them soft and fluffy. Write the name of the powder. Name the main ingredients. Explain the function of each ingredient.
(b) Write the chemical reaction taking place when the powder is heated during baking.

Fill in the blanks:
In some chemical reactions an insoluble ................... is formed when two solutions are mixed.

Write balanced chemical equations for the following word equation:
Potassium chlorate $$\rightarrow $$ Potassium chloride + Oxygen

Write balanced chemical equations for the following word equation:
Copper +Oxygen $$\rightarrow $$ Copper (II) oxide

Observe the diagram showing a copper rod kept immersed in silver nitrate solution.
a. What is the colour change of the solution?
b. Write the balanced chemical equation for the reaction.

Write symbolic representation for the following word equations and balance them:
Calcium oxide + Water $$\rightarrow$$ Calcium hydroxide

Which of the following reactions will not occurs? Why not?

(a) $$ MgSO_4 (aq) + Cu (s) \rightarrow CuSO_4(aq) +Mg (s) $$

(b) $$ CuSO_4(aq) +Fe(s) \rightarrow FeSO_4(aq) +Cu(s) $$

(c) $$ MgSO_4(aq) +Fe(s) \rightarrow FeSO_4(aq) +Mg(s) $$

Correct and balance the following equation:

$$Ca+H_2O\rightarrow CaOH+H$$

Fill in the blank with suitable words:

Anti-oxidants are often added to fat-containing foods to prevent .......... due to oxidation.

Which of the following is a combination and which is a displacement reaction?

a) $$Cl_2+2KI \rightarrow 2KCl+I_2$$

b) $$2K+Cl_2 \rightarrow 2KCl$$

Correct and balance the following equation:
$$N+H_2 \rightarrow NH_3$$

Balance the following chemical reaction:

$$MnO_2+HCl \rightarrow MnCl_2+Cl_2+H_2O$$

When a green iron salt is heated strongly, its colour finally changes to brown and odour of burning sulphur is given out.
(i) Name the iron salt and name the type of reaction that takes place during the heating of iron salt.
(ii) Write a chemical equation for the reaction involved.

Name the type of chemical reaction represented by the following equation:
(i)$$CaO+H_{2}O \longrightarrow Ca(OH)_{2}$$
(ii)$$3BaCl_{2}+Al_{2}(SO_{4})_{3} \longrightarrow 2AlCl_{3}+3BaSO_{4}$$
(iii)$$2FeSO_{4} \xrightarrow[]{Heat} Fe_{2}O_{3}+SO_{2}+SO_{3}$$

Identify the oxidising agent (oxidant) in the following reactions
$$\text { (a) } P b_{3} O_{4}+8 H C l \rightarrow 3 P b C l_{2}+C l_{2}+4 H_{2} O$$

Write the balanced chemical equations for the following reaction and identify the type of reaction.
Thermit reaction, iron (III) oxide reacts with aluminium and gives molten iron and aluminium oxide.

Identify the reducing agent in the following reaction-
$$ F e_{2} O_{3}+3 C O \rightarrow 2 F e+3 C O_{2}$$

Identify the oxidising agent (oxidant) in the following reactions
$$\text { (e) } 3 F e+4 H_{2} O \rightarrow F e_{3} O_{4}+4 H_{2}$$

Identify the oxidising agent (oxidant) in the following reactions
$$\text { (c) } C u S O_{4}+Z n \rightarrow C u+Z n S O_{4}$$

Identify the oxidising agent (oxidant) in the following reactions
$$\text { (b) } 2 M g+O_{2} \rightarrow 2 M g O$$

Identify the reducing agent in the following reactions
$$2 H_{2}+O_{2} \rightarrow 2 H_{2} O$$

Write a balanced chemical equation for each of the following reactions and also classify them.
(b) A piece of sodium metal is added to absolute ethanol to form sodium ethoxide and hydrogen gas.

Give the characteristic tests for the following gas.
$$CO_{2}$$

Give the characteristic tests for the following gas.
$$O_{2}$$

Give the characteristic tests for the following gas.
$$SO_{2}$$

On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed.
Identify the type of reaction.

Give the characteristic tests for the following gas.
$$H_{2}$$

On heating blue coloured powder of copper (II) nitrate in a boiling tube, copper oxide (black), oxygen gas and a brown gas X is formed.
Write a balanced chemical equation of the reaction.

Identify the oxidising agent (oxidant) in the following reactions
$$\text { (f) } C u O+H_{2} \rightarrow C u+H_{2} O$$

Write symbolic representation for the following word equations and balance them:
Aluminium + Chlorine $$\rightarrow$$ Aluminium chloride

Give the following a suitable word.
The smallest unit of matter which takes part in a chemical reaction.

Write the balanced chemical equation for the following word equation:
Potassium permanganate + Hydrochloric acid $$\rightarrow$$ Potassium chloride + Manganese chloride + Chlorine + Water

Write the balanced chemical equations of the following word equation:
Aluminium + sodium hydroxide + water $$\rightarrow$$ sodium meta aluminate + hydrogen

Write the balanced chemical equations of the following word equation:
Potassium dichromate + Hydrochloric acid $$\rightarrow$$ Potassium chloride + Chromium chloride + Water + Chlorine

Write the balanced chemical equations of the following word equation:
Barium chloride + Sulphuric acid $$\rightarrow$$ Barium Sulphate + Hydrochloric acid

Balance the following equations
$$P + HNO_3 \rightarrow NO_2 + H_2O + H_3PO_4$$

Divide the following redox reactions into oxidation and reduction half reactions.
$$Cl_{2} + 2Br^{-} \rightarrow Br_{2} + 2Cl^{-}$$

Divide the following redox reactions into oxidation and reduction half reactions.
$$2Cu^{+} \rightarrow Cu + Cu^{2+}$$

Write the balanced chemical equations of the following word equation:
Aluminium sulphate + sodium hydroxide $$\rightarrow$$ sodium sulphate + sodium meta aluminate + water

Write the balanced chemical equations of the following word equation:
Aluminium carbide + water $$\rightarrow$$ aluminium hydroxide + methane

Write the balanced chemical equation for the following word equation:
Sulphur + Nitric acid $$\rightarrow$$ Sulphuric acid + Nitrogen dioxide + Water

Divide the following redox reaction into oxidation and reduction half reactions.
$$Zn+Cu^{2+}\rightarrow Zn^{2+}+Cu$$