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CBSE Questions for Class 10 Chemistry Chemical Reactions And Equations Quiz 6 - MCQExams.com
CBSE
Class 10 Chemistry
Chemical Reactions And Equations
Quiz 6
In a gaseous reaction of the type, $$aA + bB \rightarrow cC + dD$$, which is wrong?
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a litres of A combines with b litres of B to give C and D
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a mol of A combines with b mol of B to give C and D
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a g of A combines with b g of B to give C and D
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a molecules of A combines with b molecules of B to give C and D
Explanation
The option C which states, "$$a$$ g of A combines with $$b$$ g of B to give C and D" is incorrect.
The correct statement is "$$a \times M_A$$ g of A combines with $$b \times M_B$$ g of B to give C and D".
Here, $$M_A$$ and $$M_B$$ are the molar masses of A and B.
$$BaCl_{2}(aq)+Na_2SO_4(aq)\rightarrow BaSO_{4}(s)+2NaCl (aq)$$
Above reaction involves which type of reaction :
(a) Displacement
(b) Precipitation
(c) Combination
(d) Double displacement
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(a) & (c)
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(a), (b) & (c)
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(b) & (c)
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(b) & (d)
Explanation
$$\displaystyle BaCl_{2}(aq)+Na_2SO_4(aq)\rightarrow BaSO_{4}(s)+2NaCl (aq)$$
The types of reactions are (b) Precipitation and (d) Double displacement.
A precipitate of $$\displaystyle Barium \: sulphate $$ is obtained.
In double displacement reaction, 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.
So, the correct option is $$D$$.
Rancidity of fats can be prevented by antioxidants.
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True
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False
Explanation
$$\text{Rancidity-}$$ It is the complete or incomplete oxidation or hydrolysis of fats and oils when exposed to air, light, moisture or by bacterial action, resulting in unpleasant taste and odour.
Rancidity can be prevented by:-
Storing foods away from light, In the absence of light the oxidation process of fats and oils slows down and thus rancidity is retarded.
A
dding antioxidants to foods containing fats and oils.
Precipitate in a reaction is indicated by which arrow mark?
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$$\rightarrow$$
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$$\uparrow$$
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$$\downarrow$$
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$$\leftarrow$$
Explanation
The precipitate is usually insoluble part or settles down in mixture (due to denser) and hence downward arrow sign is written $$(\downarrow)$$.
Which of the following process involves chemical reaction?
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Formation of ice from water
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Respiration
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Compression of sponge
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Cutting of tree
Explanation
The respiratory reaction is an example of chemical change.
Respiration is a form of oxidation.
Glucose is oxidized to $$CO_2$$ and $$H_2O$$ (along with the release of energy) at the cells by the oxygen from the air we breathe in.
$$C_6H_{12}O_6 + 6 O_2 \to 6 CO_2 + 6 H_2O$$
Since glucose is converted into new products with different composition, respiration is a chemical change.
The mixture of carbon and sulphur is separated by using the solution of _________.
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carbon dioxide
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carbon disulphide
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carbon monoxide
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sulphur oxide
Explanation
The mixture of carbon and sulphur can be separated from each other by using a solution of carbon disulphide. Sulphur gets dissolved in the solution whereas carbon remains undissolved. This mixture is then filtered to remove carbon followed by evaporation to obtain sulphur.
Which of the following is not a characteristic of a chemical reaction?
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Formation of precipitate
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Change in color
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Change in temperature
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None of the above
Explanation
A chemical reaction is characterized by:
Change in temperature
Change in colour
Change in state
Evolution of gas
Formation of precipitate
Hence, option $$D$$ is correct.
Constituents of the compounds can be separated by
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physical methods
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chemical reactions
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Both A and B
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None of A or B
Explanation
The components of a compound are chemically combined, they cannot be separated easily by physical methods, their separation requires methods like chemical reactions.
In the reaction given below, hydrogen is getting:
$$ CuO + H_2 \rightarrow Cu + H_2O $$
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reduced
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oxidized
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No change
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None of the above
Explanation
In this reaction, copper is losing oxygen and hydrogen is gaining oxygen. If a substance gains oxygen during a reaction, it is said to be oxidised. If a substance loses oxygen during a reaction, it is said to be reduced. So, in this reaction, hydrogen is getting oxidised while hydrogen is getting is reduced.
State whether the following statement is true or false:
A chemical equation can be balanced easily by altering the formula of a reactant or product.
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True
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False
Explanation
By the law of constant proportion, the chemical formula for a compound can't be changed, it's always fixed.
But the reaction is balanced by equating the number of atoms of different elements on both sides by multiplying reactant or product with whole numbers or fractions.
The color of the coating formed on the metals such as iron, silver, and copper after corrosion will be:
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Brown, black and green in colour
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Black, brown and green in colour
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Brown in colour in all the metals
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Black in colour in all the metals
Explanation
When the metal is attacked by substances around it such as moisture, acids, etc. it is said to corrode and this process is called corrosion.
After corrosion, the color of:
Iron changes to $$\rightarrow$$ Reddish brown
Silver changes to $$\rightarrow$$ black
Copper changes to $$\rightarrow$$ green
On heating the crystals of lead nitrate crystals, brown fumes are emitted.
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True
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False
Explanation
When lead nitrate is heated, decomposition reaction occurs and $$PbO$$, $$O_2$$ and $$NO_2$$ are formed. Brown fumes are nitrogen dioxide.
The reaction is as follows:
$$2Pb(NO_3)_2(s) \xrightarrow {heat} 2PbO(s) + 4NO_2(g) + O_2(g)$$
Which of the following are combination reactions?
(i) $$2 \mathrm{KClO}_{3} + {\mathrm{Heat}}{\longrightarrow} 2 \mathrm{KCl}+3 \mathrm{O}_{2}$$
(ii) $$M g O+H_{2} O \longrightarrow M g(O H)_{2}$$
(iii) $$4 A 1+3 O_{2} \longrightarrow 2 A 1_{2} O_{3}$$
(iv) $$Z n+F e S O_{4} \longrightarrow Z n S O_{4}+F e$$
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(i) and (iii)
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(iii) and (iv)
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(ii) and (iv)
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(ii) and (iii)
Explanation
In combination reaction two or more reactant combine to form single compound.
In reaction (ii) $$MgO$$ and $$H_2O$$ combines to form $$Mg(OH)_2$$
and,
In reaction (iii) $$Al$$ and $$O_2$$ combines to form $$Al_2O_3$$
Hence, these two are combination reactions. So, option $$D$$ is correct.
Reduction reaction is the exact opposite of
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displacement reaction
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decomposition reaction
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oxidation reaction
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none of these
Explanation
Reduction reaction is the opposite (or reverse reaction) to $$\text {oxidation reaction}$$.
In reduction gain of electrons takes place while in oxidation loss of electrons.
The reaction $$BaCl_2(aq) + H_2SO_4(aq) \rightarrow BaSO_4(s) + 2HCl(aq)$$ is
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Displacement reaction
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Neutralisation reaction
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Decomposition reaction
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Double displacement reaction
Explanation
The reaction $$BaCl_2(aq) + H_2SO_4(aq) \rightarrow BaSO_4(s) + 2HCl(aq)$$ is $$Double$$ $$displacement$$ reaction
One day Mohan was performing an experiment in the laboratory. By mistake he leaves the iron nail in the copper sulphate solution for one week.
After one week, the colour of sulphate
solution is:
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Green
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Yellow
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Red
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Colourless
In a combination how many products are formed?
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two only
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one or two only
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one only
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number cannot be specified
Explanation
A reaction in which single product is formed from two or more reactants is called as combination reactions.
For example, burning of coal. $$C_{(s)} + O_{{2}{(g)}}$$ $$\longrightarrow CO_{{2}{(g)}}$$
Fatty food become rancid due to the process of
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Oxidation
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Corrosion
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Reduction
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Hydrogenation
Calcium oxide reacts vigorously with water to produce slaked lime.
$$CaO(s) + H_2O(l) \to Ca(OH)_2(aq)+ Heat$$
This reaction can be classified which of the following?
(A) Combination reaction
(B) Exothermic reaction
(C) Endothermic reaction
(D) Decomposition reaction
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(A) and (C)
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(C) and (D)
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(A), (C) and (D)
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(A) and (B)
Explanation
$$CaO (s) + H_2O (l) \rightarrow Ca(OH)_2 (aq)$$
A combination reaction is a reaction where two or more elements or compounds combine to form a single compound. Calcium oxide combines with water to form calcium hydroxide. Hence, it is a combination reaction.
It is an exothermic reaction as a lot of heat liberate with a hissing sound during the reaction.
Hence, option D is correct.
Strong heating of ferrous sulphate leads to the formation of a brown solid and two gases. This reaction can be categorised as
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Displacement and redox
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Decomposition and redox
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Displacement and endothermic
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Decomposition and exothermic
Explanation
$$\bullet$$ Strong heating of ferrous sulphate $$(FeSO_4)$$ leads to the formation of a brown solid ferric oxide $$(Fe_2O_3)$$ and two gases, sulphur dioxide $$(SO_2)$$ and sulphur trioxide $$(SO_3)$$ are formed.
$$\bullet$$
This is a decomposition reaction where, single reactant ferrous sulphate
$$(FeSO_4)$$
decomposes to form three different products i.e.,
ferric oxide $$(Fe_2O_3)$$ and two gases, sulphur dioxide $$(SO_2)$$ and sulphur trioxide $$(SO_3)$$.
$$\bullet$$ The reaction involved are as follows:
$$2FeSO_4 (s)\rightarrow Fe_2O_3(s) + SO_2(g) + SO_3(g)$$
$$\bullet$$ In addition, the oxidation state of $$S$$ changes from $$+6$$ in
$$FeSO_4$$ to $$+4$$ in
$$SO_2$$, causing reduction.
$$\bullet$$ The oxidation number of iron changes from $$+2$$ in
$$FeSO_4$$ to $$+3$$ in
$$(Fe_2O_3)$$, causing oxidation.
$$\bullet$$ It is a redox reaction because $$Fe(II)$$ is oxidised to $$Fe(III)$$ and $$S(IV)$$ is reduced to $$S(IV)$$.
$$\text{Additional information}$$
$$\bullet$$ Any chemical reaction in which the oxidation number of a molecules, atom, or ions changes by gaining or losing an electron is known as redox reaction.
$$\bullet$$ Oxidation is a loss of electrons.
$$\bullet$$ Reduction is a gain of electrons.
$$\text{Which one of the following does not result in the evolution of}\ H_{2} \text{gas? }$$
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Zinc and hydrochloric Acid
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Aluminium and Nitric Acid
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Iron and Sulphuric Acid
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Magnesium and very dilute nitric acid
Explanation
Correct option is (b)
$$\text{Solution}$$
$$\text{Explanation for correct option}$$
(b)
When aluminium(Al) reacts with nitric acid$$(HNO_3)$$, it gives aluminium nitrate$$[Al(NO_3)_3]$$, nitrogen dioxide$$(NO_2)$$ and water.
$$\bullet$$ The chemical reaction involved is as follows:
$$Al + 6HNO_3\rightarrow Al(NO_3)_3 + 3NO_2 + 3H_2O$$
$$\text{Explanation for incorrect options}$$
(a)
When zinc(Zn) react with hydrochloric acid$$(HCl)$$, zinc chloride$$(ZnCl_2)$$ and hydrogen gas are formed.
$$\bullet$$ The chemical reaction involved is as follows:
$$Zn + 2HCl\rightarrow ZnCl_2 + H_2$$
(c)
When iron(Fe) reacts with dilute sulphuric acid$$(H_2SO_4)$$, ferrous sulphate$$(FeSO_4)$$ with the evolution of hydrogen gas is formed.
$$\bullet$$ The chemical reaction involved is as follows:
$$Fe + H_2SO_4\rightarrow FeSO_4 + H_2$$
(d)
$$\bullet$$
When magnesium(Mg) reacts with very dilute nitric acid
$$(HNO_3)$$
, it forms magnesium nitrate$$[Mg(NO_3)_2]$$ and hydrogen gas is evolved.
$$\bullet$$ The chemical reaction involved is as follows:
$$Mg + 2HNO_3\rightarrow Mg(NO_3)_2 + H_2$$
Barium chloride on reacting with ammonium sulphate forms barium sulphate and ammonium chloride. Which of the following correctly represents the type of the reaction involved?
(i) Displacement reaction
(ii) Precipitation reaction
(iii) Combination reaction
(iv) Double displacement reaction
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(i) only
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(ii) only
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(iv) only
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(ii) and (iv)
Explanation
$$BaCl_{2} + (NH_{4})_{2}SO_{4}$$ $$\rightarrow$$ $$BaSO_{4} + 2NH_{4}Cl $$
Above reaction is a double displacement reaction as ions (both cations and anions) of the reacting molecules are exchanged. Barium ion ($$Ba^{2+}$$) combines with sulphate ion ($$SO_{4}^{2-}$$) to form Barium sulphate ($$BaSO_{4}$$) and ammonium ion $$ (NH_{4}^{+})$$ combines with chloride ion$$(Cl^{-}$$) ion to form ammonium chloride ($$NH_{4}Cl$$).
The above reaction is also classified as a precipitation reaction because barium and sulphate ions combine to form precipitates of barium sulphate.
$$Ba^{2+} (aq) + SO_{4}^{2-} (aq) \rightarrow BaSO_{4}$$(s)
Option D is correct.
Identify an element combination reaction from the following.
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$$2Pb(NO_{3})_{2} \rightarrow 2PbO + 4NO_{2} + O_{2}$$
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$$2Al_{2}O_{3} \rightarrow 4Al + 3O_{2}$$
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$$S + O_{2} \rightarrow SO_{2}$$
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$$2CO + O_{2} \rightarrow 2CO_{2}$$
Explanation
A reaction in which two or more reactants combine to form a single product is known as a combination reaction. Among the given options, option C is an element combination reaction since Sulphur reacts with oxygen to form $$SO_2.$$
$$\therefore$$ The correct option is $$C$$.
Lead nitrate on decomposition gives:
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lead oxide
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nitrogen dioxide
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oxygen
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nitrogen
Explanation
Lead nitrate decomposes in the presence of heat to give lead oxide, nitrogen dioxide, and oxygen.
$$2Pb(NO_3 )_2 \xrightarrow{\Delta} 2PbO + 4NO_2 + O_2$$
A magnesium ribbon is burnt in oxygen to give a white compound $$X$$ accompanied by
the emission
of light. If the burning ribbon is now placed in an atmosphere of nitrogen, it continues to burn and forms a compound $$Y$$.
Write the chemical formula of $$X$$ and $$Y$$:
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$$x \rightarrow MgO ; y\rightarrow MgN$$
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$$x \rightarrow 2MgO ; y\rightarrow Mg_{2}N_{3}$$
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$$x \rightarrow MgO ; y\rightarrow Mg_{3}N_{2}$$
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None of these
Explanation
Magnesium ribbon burns in oxygen($$O_{2}$$) to form magnesium oxide ($$MgO$$).
$$2Mg + O_{2} \rightarrow 2MgO$$
Therefore $$X$$ is $$MgO$$.
Burning magnesium ribbon reacts with nitrogen($$N_{2}$$) to form
magnesium nitride($$Mg_{3}N_{2}$$).
$$3Mg + N_{2} \rightarrow Mg_{3}N_{2}$$
Therefore, $$Y$$ is $$Mg_{3}N_{2}$$
Hence the correct option is C.
Identify the type reaction from the following.
$$H_2CO_3 (aq) \rightarrow H_2O(l) + CO_2(g)$$
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Combustion reaction
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Decomposition reaction
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Displacement
reaction
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Double displacement reaction
Explanation
$$H_2CO_3 (aq) \rightarrow H_2O(l) + CO_2(g)$$
In this reaction, carbonic acid decomposes to form water and carbon dioxide gas. Hence, this is the example of a decomposition reaction.
When sodium hydroxide solution is added to copper sulfate solution, a blue precipitate of copper hydroxide is formed along with sodium sulfate solution. What kind of chemical reaction takes place between them?
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Chemical combination reaction
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Chemical decomposition reaction
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Chemical displacement reaction
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Chemical double decomposition reaction
Explanation
Copper sulfate solution reacts with sodium hydroxide solution to form a precipitate of copper hydroxide along with sodium sulfate solution.
It is a chemical double decomposition reaction.
According to the equation:
$$2NaOH+CuSO_4→Na_2SO_4+Cu(OH)_2↓$$
$$KMnO_4+H_2SO_4+FeSO_4 \rightarrow K_2SO_4 + MnSO_4+Fe_2(SO_4)_3+H_2O$$
Coefficients of sulphuric acid and ferric sulphate in the balanced equation of above reaction are______and ______respectively.
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8, 4
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5, 8
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4, 3
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8, 5
Explanation
The balanced equation can be written as:
$$2KMnO_{4} + 8H_{2}SO_{4} + 10FeSO_{4} \rightarrow K_{2}SO_{4} + 2MnSO_{4} + 5Fe_{2}(SO_{4})_{3} + 8H_{2}O$$
Coefficient of Sulphuric acid, $$H_2SO_4 = 8$$
Coefficient of
Ferric sulphate, $$Fe_2(SO_4)_3 = 5$$
Therefore option D is correct answer.
Sodium bicarbonate on decomposition forms:
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$$NaHCO_3$$
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$$Na_2CO_3$$
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$$Na_2CO_3 . 10H_2O$$
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None of these
Explanation
Sodium bicarbonate on decomposition forms sodium carbonate, water, and carbon dioxide.
$$\displaystyle 2NaHCO_3 \xrightarrow {heat} Na_2CO_3+H_2O+CO_2$$
Which of the following pairs will give displacement reactions?
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$$NaCl$$ solution and copper metal
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$$Mg{ Cl }_{ 2 }$$ solution and aluminium metal
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$$FeS{ O }_{ 4 }$$ solution and silver metal
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$$AgN{ O }_{ 3 }$$ solution and copper metal.
Explanation
Metal above in activity series are more reactive and can displace the less reactive metal.
(a) $$NaCl$$ solution and copper metal
$$Na$$ is more reactive than $$Cu$$, thus it will not give diplacement reaction.
(b) $$MgCl_2$$ solution and aluminium metal.
$$Al$$ can not replace $$Mg$$ because it is lower on the reactivity series.
(c) $$FeSO_4$$ solution and silver metal
$$Ag$$ can not replace $$Fe$$ because it is lower on the reactivity series.
(d) $$AgNO_3$$ solution and copper metal.
$$Ag$$ can be replaced by $$Cu$$ as it is above silver in the reactivity series. Therefore, this pair will give displacement reaction.
$$AgNO_3 + Cu \rightarrow Cu(NO_3)_2 + Ag$$
Hence, option $$D$$ is correct.
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