Class 12 Engineering Chemistry - Surface Chemistry

What is adsorption?

The phenomenon in which the molecules of a substance are attracted and adhered to the surface of a solid or liquid is called adsorption.

Name the two groups into which phenomenon of catalysis can be divided. Given an example of each group with the chemical equation involved.

The phenomenon of catalysis is basically the ability to increase the rate of a chemical reaction, or more specifically the rate at which equilibrium is attained. This is achieved by employing a catalyst. Catalysis can be divided into two classes;

(i) Homogeneous catalysis:

When the reactant and catalyst are in the same phase

$2SO_2 (g)+ O_2(g) \overset {NO(g)}{\longrightarrow} 2SO_3(g)$

(ii) Heterogeneous catalysis:

When the reactant and catalyst are in a different phase

$N_2(g) + 3H_2(g) \overset {Fe(s)}{\longrightarrow} 2NH_3(g)$

The catalyst used for hydrogenation of oils is __________.

Hydrogenation is the general process to treat with hydrogen which is a chemical reaction between molecular hydrogen ( $H_2$ ) and another compound or element, usually in the presence of a catalyst such as nickel, palladium or platinum. The process is commonly employed to reduce or saturate organic compounds.

How is Soap industrially manufactured?

Industrially, soaps are manufactured by saponification. Fat is hydrolyzed by using sodium or potassium hydroxide solution.

Write briefly about the preparation of colloids by chemical methods.

i) Double decomposition
An Arsenic sulphide Sol is prepared by passing a slowstream of hydrogen sulphide gas through a cold solution of arsenious oxide. This is continued till the yellow colour of sol attains maximum intensity.

$As_2O_3 +3H_2S \rightarrow \underset{yellow}{As_2S_3}+3H_2O$
Excess hydrogen sulphide is removed by passing in a stream of hydrogen.
ii) Oxidation : A colloidal solution of sulphur is obtained by passing

$H_2S$ into solution of sulphur dioxide.

$2H_2S+SO_2\rightarrow 2H_2O+3S$
iii) Reduction : Silver.sols and gold sols can be obtained by treating dilute solution of silver or gold chloride with organic reducing agents like tannic acid or formaldehyde.

$AgNO_3 \rightarrow tannic \,\, acid\rightarrow AgSol$

$AgCul_3 \rightarrow tannic \,\, acid\rightarrow AuSol$
iv) Hydrolysis : Colloidal solutions of the hydroxides of FelCr, Al etc, can be prepared by hydrolysis of their salts. A colloida solution of ferric hydroxide, is obtained by boiling a dilute solution of ferric chloride.

$FeCl_3 +3H_2O\rightarrow \underset{red \,\, sol}{Fe(OH)_3}+3HCl$

What is catalysis? Give an example.

A catalyst is a substance which alters the speed of a chemical reaction without itself undergoing any chemical change and the phenomenon is known as catalysis.

Name the adsorbent used to removal of colouring matter from solution.

Activated charcoal is the adsorbent used to removal of colouring matter from solution. The colouring matter is adsorbed on activated charcoal.

The conductance of an emulsion increases on adding common salt. What type of emulsion is this?

This is oil in water type emulsion. The The conductivity increases by adding ionic compounds which dissociate in water. Here,

$NaCl$ gives

$Na^+$ and

$Cl^-$ which increases conductance of emulsion.

The emulsifying agent forms an interfacial film between suspended particles and the medium. The principal emulsifying agents for $O/W$ emulsions are?

Emulsions can exist as Oil in water or Water in oil of emulsions.

The type of emulsion depends upon the properties of the dispersed phase and continuous phase. If the oil phase is dispersed in a continuous aqueous phase the emulsion is known as Oil in water.

Explain cleaning action?

Cleansing action of soaps :

The dirt present on clothes is organic in nature and insoluble in water. Therefore, it cannot be removed by only washing with water. When soap is dissolved in water, its hydrophobic ends attach themselves to the dirt and remove it from the cloth. Then, the molecules of soap arrange themselves in micelle formation and trap the dirt at the centre of the cluster. These micelles remain suspended in the water. Hence, the dust particles are easily rinsed away by water.

Describe the cleansing action of soap?

Cleansing action of soaps :

The dirt present on clothes is organic in nature and insoluble in water. Therefore, it cannot be removed by only washing with water. When soap is dissolved in water, its hydrophobic ends attach themselves to the dirt and remove it from the cloth. Then, the molecules of soap arrange themselves in micelle formation and trap the dirt at the centre of the crustel. These micelles remain suspended in the water. Hence, the dust particles are easily rinsed away by water.

Name the temperature above which the formation of micelles takes place.
What type of semiconductor is obtained when silicon is doped with arsenic ?

The temperature at which the formation of micelles takes place is called as Kraft temperature.

n-type Semiconductor is formed when silicon is doped with arsenic.

During the decomposition of hydrogen peroxide glycerine acts as positive catalyst. If this is true enter 1 and if false enter 0.

A positive catalyst is nothing but the substance which increases the rate of reaction.In case of hydrogen peroxide decomposition as soon as the catalyst is added, an eruption of foam flies out of the top of the gas column and then the decomposition becomes easy.Hence we use potassium iodide solution as the catalyst but not glycerine.Hence given statement is false.

Explain the mechanism of cleaning action of soap.

1) Soap molecules are the long chain of carboxylic acids with sodium or potassium at one end.

2) Since the dirt is mostly oily in nature which does not dissolve in water, the carbon chain dissolves in oily dirt and ionic end dissolves in water.

Match the List I with the List II.

1) Homogeneous catalysts as reactant and product phases are different and it is a example of Positive catalyst.

2) Heterogeneous catalysts as reactant and product phases are different and it is a example of Negative catalyst.

3) Heterogeneous catalysts as reactant and product phases are different and it is a example of Negative catalyst.

4) Homogeneous catalysts as reactant and product phases are different and it is a example of Positive catalyst.

_________ (Adsorption/Chemisorption) process is involved in the decolourisation of sugar cane juice.

Activated charcoal is used in the decolorization of sugar cane juice. It adsorbs the coloured impurities on its surface.

Therefore adsorption is the process, involved in the decolourisation of sugar cane juice.

Match list I with list II.

A Catalyst is a substance which acclerates the rate of a chemical reaction without undergoing any change in its chemical composition or massduring the reaction. A catalyst acclerates the rate of a reaction by lowering the activation energy.

They are of 2 types

Homogeneous Catalysis : When catalysts and reactants are in same phase then the process is said to be homogeneous catalysis

Eg : (i)

$2SO_2(g)+O_2(g) \overset{No(g)}{\longrightarrow} 2SO_3(g)$

(ii)

$CH_3COOCH_3(l) \overset{HCI(l)}{\longrightarrow} CH_3COOH(aq)$

(iii)

$C_{12}H_{22}O_{11}(aq.)+H_2O(l) \overset{H_2SO_4(l)}{\longrightarrow} C_6H_{12}O_6(aq.)+C_6H_{12}O_6(aq.)$

Glucose Fructose

Heterogenous Catalysis : When catalysts and reactants are in different phases, then process a know as heterogenous catalysis and catalyst is called heterogeneous catalyst

Eg : (i)

$2SO_3(g) +O_2(g)\overset{Pt(s)}{\longrightarrow}2SO_3(g)$

(ii)

$N_2(g)+3H_2(g)\overset{Fe(s)}{\longrightarrow} 2NH_3(g)$

(iii)

$4NH_3(g)+5O_2(g)\overset{Pt(s)}{\longrightarrow} 4NO(g)+6H_2O(g)$

(iv)

$Vegetable\, oil (l)+H_2(g) \overset{Ni(s)}{\longrightarrow} Vegetable \, ghee(s)$ .

The reaction having catalyst and reactants phase $\geq$ ____________ is heterogeneous catalysis.
$1$
$2$
$3$
$0$

Heterogeneous catalysis involves the use of a catalyst in a different phase from the reactants. Typical examples involve a solid catalyst with the reactants as either liquids or gases. So, this involves atleast two different phases.

The reaction in which reactants and the catalyst have one phase is _________ .
heterogeneous catalysis
homogeneous catalysis
solid state catalysis
solution catalysis

A Catalyst is a substance which accelerates the rate of a chemical reaction without undergoing any change in its chemical composition or mass during the reaction. A catalyst accelerates the rate of a reaction by lowering the activation energy.

Catalysts are of 2 types

i) Homogeneous catalyst: When reactant and catalyst are in same phase. In this catalysis, the catalyst combines with one of the reactants to form some intermediate compound, which is unstable and decomposes easily to form the product.

ii) Heterogeneous catalyst: When reactant and catalyst are in different phases. These are surface catalyst which acts through adsorption.

So, homogeneous catalysis has the catalyst in the same phase as the reactants. Typically everything will be present as a gas or contained in a single liquid phase.

The phenomenon when a reaction influences the rate of other reaction is ___.

homogenous catalysis
heterogeneous catalysis
induced catalysis
competitive catalysis

When one reaction influences the rate of other reaction, which does not occur under ordinary conditions, then this phenomenon is induced catalysis.

Example:

Sodium sulphite solution oxidises in the air but sodium arsenite solution does not oxidise by passing air.But when both solutions are mixed and the air is passed through the solution, then both the substances get oxidised.

The substance that __________ the activity of catalysts is poisoner.
increases
decreases
maintains
none

Promoters/Activators : Substance which themselves are not catalyst but its presence can increase the catalytic activity of catalyst. A promoters increase the number of active sites on the surface.

Catalytic Poisons/ Anti catalysts/ Catalyst Inhibitor are those substances which themselves are not catalyst but whose presence decreases the activity of the catalyst. Poisoning is due to preferential adsorption of poison on the surface of the catalyst.

The substance that _________ the activity of catalysts is called promoter.
Increases
Decreases
Maintains
None of the above

Promoters/Activators : Substance which themselves are not catalyst but its presence can increase the catalytic activity of catalyst. A promoters increase the number of active sites on the surface.

Match the following.
List-A
List-B
List-C
(A) Lyophilics
Froth floatation
a. Charge depends on pH
(B) Lyophobics
Organic substances
b. Charge is independent of pH
(C) Protection
Artificial rain
c. Digestion of food
(D) Smoke
Inorganic substances
d. Spray of Agl
(E) Coagulation
Blue tinge
e. Gelatin
(F) Emulsification
Gold number
f. Tyndall effect

If A matches with a and with number $2$ . What number does F match with?

If A matches with a and with number

$2$ , F matches with number

$1$ .
The principle of emulsification is used in froth floatation process.

Rivers on meeting with oceans form ____________ .
estuaries
swamps
deltas
none of the above

Choose the correct option.

A river delta is a landform that forms at the mouth of a river where the river flows into an ocean, sea, estuary, lake or reservoir.

Deltas form from deposition of sediment carried by a river as the flow leaves its mouth. Over long periods, this deposition builds the characteristic geographic pattern of a river delta.

Electrostatic precipitation of carbon from smoke is used to control what type of pollution?
Air
Soil
Both 1 and 2
None of the above

Electrostatic precipitator, a device that uses an electric charge to remove certain impurities either solid particles or liquid droplets from air or other gases in smoke stacks and other flues. The precipitator functions by applying energy only to the particulate matter being collected without significantly impeding the flow of gases. Originally designed for recovery of valuable industrial-process materials, electrostatic precipitators are used for air pollution control, particularly for removing particles from waste gases at industrial facilities and power-generating stations.

In oil solution of soap, the head is towards the surface of the oil and the tail is pointing away from the oil.
If the given statement is true, enter 1, else enter 0.

In oil solution of soap, the tail is towards the surface of the oil and the head is pointing away from the oil. The head is polar and the tail is non-polar. Water is polar and oil is non-polar. As we know that like attracts like, the polar head is towards the water and non-polar tail is towards oil.

Draw the diagram showing micelle formation by the following detergent.
$CH_3(CH_2)_{10}CH_2OS\overline{O}_3\overset {+}{N}a$

Micelle is formed such that hydrophobic tails form core and hydrophillic part are immersed in surrounding liquid.

1175543_237599_ans_736b8dbf84ca4b5588e0260b6de14ff7.PNG

Explain the mechanism of the cleansing action of soaps?

A molecule of soap has two dissimilar ends. At one end it is the hydrocarbon chain, which is water repellent and the other end is carboxylate anion which is a polar end. When soap is dissolved in water, many molecules come together and form a group called micelle. These micelles are formed because their hydrocarbon chains come together and the polar ends are projected outward. When a cloth with a spot of oil is soaked into a soap solution, soap dissolves tiny oil droplets by the hydrophobic end in the middle of the micelle. Due to the outer polar ends, these micelles dissolve in water and are washed away. In this way cloth gets cleaned
2067814_245574_ans_a365303da53045f983713393c19635da.jpg

2067814_245574_ans_a365303da53045f983713393c19635da.jpg

In aqueous solution of soap, head is towards the surface of water and tail is pointing away from the water.
if true, enter 1, else enter 0.

In aqueous solution of soap, the head is towards the surface of water and tail is pointing away from the water. Head is polar and the tail is non-polar. Water is polar and oil is non-polar. As we know that like attracts like, the polar head is towards the water and the non-polar tail is towards oil.

Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents like ethanol also?

Hint: Micelle contains a hydrophobic tail which is insoluble in water and a hydrophilic head which is soluble in water.

Explanation:

· The molecules of soap have two ends. One end of the molecule is hydrophilic, whereas the other is hydrophobic.

· When soap is dissolved in water and garments are soaked in it, soap molecules converge in a predictable pattern to form a structure known as a micelle.

· The micelle is a spherical structure formed by the hydrophobic ends of various molecules surrounding a grease particle.

· The hydrophilic end is on the outside of the sphere, whereas the hydrophobic end is closer to the center.

· Micelle production occurs when soap is applied to water for this reason.

· Micelle can only form around suspended oil molecules in a mixture, and soap in the form of a micelle can clean because the oily debris is trapped inside.

· Diagrammatically the formation of a micelle is shown as below;

How Does Soap Work? - Ida's Soap Box

Adsorption is a phenomenon of accumulation of higher concentration of one substance on the surface of another.
State whether True or False.

The phenomenon of accumulation of higher concentration of one substance on the surface of another than in bulk is known as adsorption. For example: silica gel adsorbs water vapors. Charcoal adsorbs ammonia.

Peptization is a process of converting a freshly prepared precipitate into a colloidal form by the addition of a suitable electrolyte.

State whether the statement is True or False.

The process of converting a freshly prepared precipitate into colloidal form by the addition of a suitable electrolyte is called peptization.

The electrolytes used for the purpose are called peptizing agents. So, the correct statement is true.

Water which gives good lather readily with soap is known as hard water.

If this is true enter 1, if false enter 0.

Hard water is often indicated by a lack of lather formation when soap is agitated in water. Hard water is water that has high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone and chalk which are largely made up of calcium and magnesium carbonates.

Adsorption is surface phenomenon and absorption is bulk phenomenon
If this is true enter 1, if false enter 0.

Answer 1

Adsorption is surface phenomenon and absorption is bulk phenomenon.

The molecules undergoing absorption are taken up by the volume, but in the case for adsorption, its done by surface.

If both absorption and adsorption occur simultaneously it is called sorption
If this is true enter 1, if false enter 0.

When both Adsorption and Absorption processes take place simultaneously, the process is called sorption.

Match various processes in surface chemistry from List 1 with their definition from List 2.

In surface chemistry,

1. Dissipation/ Desorption is the process of removing an adsorbed substance from a surface on which it is absorbed.

2. Absorption is a process in which the substance (adsorbate) is uniformly distributed throughout the bulk.

3. Sorption is a process where both the phenomenon of adsorption and absorption take place simultaneously.

4. Physisorption is a type of adsorption where weak Van der Waals forces act between the adsorbate and adsorbent.

Thus the correct combination of an answer will be A-2, B-3, C-4, D-1

The liquid or solid on the surface of which the molecule of the substance are adsorbed is called adsorbate.
If this is true enter 1, if false enter 0.

Answer 0

The liquid or solid on the surface of which the molecule of the substance are adsorbed is called absorbent. It has power or capacity or tendency to absorb or soak up something. Absorbate is a material that has been or is capable of being absorbed.

The substance whose molecules are adsorbed is called adsorbent.
If this is true enter 1, if false enter 0.

Answer 0

The substance whose molecules are adsorbed is called Absorbate which is a material that has been or is capable of being absorbed.. The liquid or solid on the surface of which the molecule of the substance are adsorbed is called absorbent.

Label the hydrophilic and hydrophobic parts in the following compounds.
(i) $CH_3(CH_2)_{10}CH_2OS\overline{O}_3\overset{+}{N}a$
(ii) $CH_3(CH_2)_{15}\overset{+}{N}(CH_3)_3\overline{B}r$
(iii) $CH_3(CH_2)_{16}COO(CH_2CH_2O)_nCH_2CH_2OH$

The hydrophilic and hydrophobic parts in the following compounds are as shown.

$\underbrace {CH_3(CH_2)_{10}CH_2}_{hydrophobic \, part}$

$\underbrace {OS\overset{-}{O_{3}}\overset{+}{N}a}_{hydrophilic \, apart}$

$\underbrace {CH_3(CH_2)_{15}}_{hydrophobic \,part}$

$\underbrace {\overset{+}{N}(CH_3)_3\overset{-}{B}r}_{hydrophilic \, part}$

$\underbrace {CH_3(CH_2)_{16}}_{hydrophobic \, part}$

$\underbrace {COO(CH_2CH_2O)_nCH_2CH_2OH}_{hydrophilic \, part}$

Explain the cleansing action of soaps.

Polar end (end with sodium or potassium ion) of soap is hydrophilic (attracted towards water) and the non polar end (the hydrocarbon part) is hydrophobic (attracted towards hydrocarbons).
On dissolution in water, the hydrophobic ends attach themselves to dirt and remove it from the cloth.
Soap molecules form micelle and trap the dirt at the center of the cluster. They remain suspended in water like particles of colloidal solution. The trapped dust particles are easily rinsed away with water.

(i) Differentiate between adsorption and absorption.
(ii) Out of $Mg{Cl}_{2}$ and $Al{Cl}_{3}$ , which one is more effective in causing coagulation of negatively charged sol and why?
(iii) Out of sulphur sol and proteins, which one forms multimolecular colloids?

(i) Absorption is the process in which a fluid is dissolved by a liquid or a solid (absorbent). Adsorption is the process in which atoms, ions or molecules from a substance (it could be gas, liquid or dissolved solid) adhere to a surface of the adsorbent. Adsorption is a surface-based process where a film of adsorbate is created on the surface while absorption involves the entire volume of the absorbing substance.

(ii) According to Hardy Schulze rule,

$AlCl_3$ with high positive charged cation

$(Al^{3+})$ will coagulate more effectively than

$MgCl_2$ . Effectiveness of the salt in causing flocculation depends on the charge of the ion. Trivalent ions are much more effective than divalent ions as according to the Hardy – Schultz Law, “Greater the valency of oppositely charged ions of the electrolyte being added, the faster is coagulation”.

(iii) Sulphur sol form multimolecular colloids. Multimolecular Colloids are in which large number of atoms or smaller molecules of a substance on dissoluton aggregate together to form species having size in the colloidal range (diameter <1 nm). Aa sulphur sol consists of particles containing a thousand or more of

$s_8$ sulphur molecules. Proteins have large molecular masses and called Macromolecular colloids.

Give one example each of lyophobic sol and lyophillic sol.

Metal sols like Gold sol and metal sulphide sols like

$As_{2}S_{3}$ sol are the examples of lyophobic sols.

The sols of proteins, starch in water, rubber in benzene, cellulose nitrate or cellulose acetate in acetone are examples of lyophilic sols.

Explain the following terms giving one example for each:
(i) Micelles
(ii) Aerosol

(i) Micelles is an organized auto-assembly formed in a liquid and composed of amphiphilic macromolecules. Surfactant molecules dispersed in a liquid colloid. A typical micelle in aqueous solution forms an aggregate with the hydrophilic "head" regions in contact with surrounding solvent, sequestering the hydrophobic single-tail regions in the micelle centre. This phase is caused by the packing behavior of single-tail lipids in a bilayer. For example when greasy dirt is mixed with soapy water, the soap molecules arrange themselves into tiny clusters called micelles.

(ii) An aerosol is a colloid of fine solid particles or liquid droplets, in air or another gas. Aerosols can be natural or artificial. Examples of natural aerosols are fog, forest exudates and geyser steam. Examples of artificial aerosols are haze, dust, particulate air pollutants and smoke.

What are the dispersed phase and dispersion medium in milk?

Give one example each of 'oil in water' and 'water in oil' emulsion.

A colloidal system in which one liquid is dispersed in another liquid immiscible with it is called an emulsion.

Types of emulsion:
(1) Emulsion of oil in water
Disperse phase is oil. Dispersion medium is water.
For example, milk consists of liquid fat particles dispersed in water.

(2) Emulsion of water in oil
Disperse phase is water and the dispersion medium is oil.
For example, cod liver oil consists of particles of water dispersed in oil.

A delta is formed at the meeting point of sea water and river water. Why?

River water is a colloidal solution of clay and sea water contains a number of electrolytes. When river water meets the sea water, the electrolytes present in the sea water coagulate the colloidal solution of clay resulting in its deposition with the formation of delta.

What are emulsions? What are their different types? Give one example of each type.

An emulsion is a mixture of two or more liquids that are normally immiscible (non-mixable or unblendable). It means that in an emulsion the dispersed phase and dispersion medium are both liquids.

There are two basic types of emulsions: oil in water and water in oil.

In every emulsion, there is a continuous phase (dispersion medium) that suspends the droplets of the other element which is called the dispersed phase.

(i) Oil-in-water emulsions (O/W): The emulsion in which oil is present as the dispersed phase and water as the dispersion medium (continuous phase) is called an oil-in-water emulsion. Milk is an example of the oil-in-water type of emulsion. In milk liquid fat globules are dispersed in water. Other examples are vanishing cream etc.
ii) Water-in-oil emulsion (W/O) : The emulsion in which water forms the dispersed phase, and the oil acts as the dispersion medium is called a water-in-oil emulsion. These emulsions are also termed oil emulsions. Butter and cold cream are typical examples of these types of emulsions. Other examples are cod liver oil etc.

Define peptization.

Peptization is the process responsible for the formation of stable dispersion of colloidal particles in the dispersion medium. In other words, it may be defined as a process of converting a precipitate into a colloidal sol by shaking it with dispersion medium in the presence of a small amount of electrolyte.

Ex: A reddish-brown colored colloidal solution is obtained by adding a small quantity of ferric chloride solution to the freshly precipitated ferric hydroxide.

A precipitate of silver iodide can be peptized by shaking with a dilute solution of silver nitrate or KI.

What are emulsions? What are their different types? Give one example of each type.

A colloidal system in which one liquid is dispersed in another liquid immiscible with it is called an emulsion.
Types of emulsion:
(1) Emulsion of oil in water:
Disperse phase is oil. Dispersion medium is water.
For example, milk consists of liquid fat particles dispersed in water.
(2) Emulsion of water in oil:
Disperse phase is water and dispersion medium is oil.
For example, cod liver oil consists of particles of water dispersed in oil.

What is meant by 'shape selective catalysis'?

A catalytic reaction which depends upon the pore structure of the catalyst, on the size of the reactant and the product molecules is called shape selective catalysis. Shape-selective catalysis is important for synthesis of organic chemicals and for processing of petroleum fractions and fuels.

For example, catalysis by zeolites is called shape selective catalysis. The pore size in zeolites ranges from 260-740pm. Thus, molecules having pore size more than this cannot enter the zeolite and undergo the reaction.

Define the following terms with an example in each case:
(i) Macromolecular sol (ii) Peptization (iii) Emuslion

i. Macromolecular sol: They are molecules of large size having high molecular masses. Due to long chain, the vander waal's forces are stronger, e.g., rubber, nylon etc.

ii. Peptization is the process responsible for the formation of stable dispersion of colloidal particles in dispersion medium. In other words, it may be defined as a process of converting a precipitate into colloidal sol by shaking it with dispersion medium in the presence of small amount of electrolyte.
iii. Emulsion is a fine dispersion of minute droplets of one liquid in another in which it is not soluble or miscible, e.g. milk.

What is the difference between oil/water (O/W) type and water/oil (W/O) type emulsions? Give an example of each type.

In an oil-in-water emulsion, the continuous phase is the water and the dispersed phase is the oil while in a water-in-oil emulsion the oil is the continuous phase. Oil-in-water emulsions are common in food products.
a. Cream (foam) in espresso – coffee oil in water (brewed coffee).
b. Homogenized milk – an emulsion of milk fat in water and milk proteins.
Water-in-oil emulsions are less common in food.
c. Butter – an emulsion of water in butterfat.

What are the characteristics of the following colloids? Give one example of each
(i) Multimolecular colloids (ii) Lyophobic sols (iii) Emulsions

1. They are formed by the aggregate of a large number of atoms or molecules which generally have diameters less than 1 nm, e.g., sols of gold, sulphur etc.

2. Lyophobic sols: These sols are usually formed by the inorganic materials like metals, their sulphides etc.They are irreversible in nature i.e. once precipitated cannot return the colloidal sol by simply addition of the dispersion medium.

3. Emulsions: An emulsion is a mixture of two or more liquids that are normally immiscible. There are two basic types of emulsions: oil-in-water (O/W) and water-in-oil (W/O). In an emulsion, one liquid (the dispersed phase) is dispersed in the other (the continuous phase). Examples of emulsions include vinaigrette, milk, mayonnaise.

Explain the cleansing action of soap.

When soap is dissolved in water, its hydrophobic ends attach themselves to dirt and remove it from the cloth. First, the molecules of soap arrange themselves in micelle formation and trap the dirt at the centre of the cluster. These micelles remain suspended in water like particles in a colloidal solution.

The various micelles present in water do not come together to form a precipitate as each micelle repels the other because of the ion-ion repulsion. Thus, the dust particles remain trapped in micelles (which remain suspended) and are easily rinsed away with water.

Hence, soap micelles remove dirt by dissolving it in water.

Give one example (equation) of a homogeneously catalysed reaction and name the catalyst.

Hydrolysis of ethyl acetate to give ethanol and acetic acid is catalysed by dil

$H_2SO_4$ .

$\underset{ethyl \,acetate}{CH_3COO.C_2H_5} + \underset{water}{HOH}\xrightarrow[dil. H_2SO_4]{Catalyst} \underset{acetic \,acid}{CH_3COOH} + \underset{ethanol}{C_2H_5OH}$

(a) What is enzyme catalysis? Write an example.
(b) Which type of emulsion is milk? Explain.
(c) Explain Electrophoresis with labelled diagram.

(a) Enzyme catalysis: refers to various reactions (catalysed by enzymes) that occurs in the bodies of animals and plants to maintain life processes. An example of enzyme catalysis is inversion of can sugar

$\displaystyle C_{12}H_{22}O_{11} + H_2O \xrightarrow {\text {invertase}} C_6H_{12}O_6 \text {(glucose)}+C_6H_{12}O_6 \text {(fructose)}$

(b) Milk id oil in water type emulsion. The dispersed phase is oil and the dispersion medium is water.
(c) Electrophoresis: Charged colloidal particles migrate to electrode having opposite charge under the influence of an electric field.

a) Explain bragg's spectrometer method.
b) Write about the preparation of colloids by chemical methods.

a) Bragg's spectrometer method is used for studying crystals using X-rays.
The apparatus consists of a X-ray tube from which a narrow beam of X-rays is allowed to fall on the crystal mounted on a rotating table. The rotating table is provided with scale and vernier from which the angle of incidence

$\theta$ can be measured.
An arm which is rotating about the same axis as the crystal table, carries an ionization chamber. The rays reflected from crystal enter into the ionization chamber and ionize the gas present inside. Due to the ionization, current produced is measured by electrometer. The current of ionization is a direct measure of intensity of reflected beam from the crystal. For different angles of incidence, the corresponding ionization current is measured from the electrometer. These values are plotted in the form of graph.
For sodium chloride, the maximum reflection for peaks for 100 plane occurred at

$\theta =5.9^{0},11.85^{0}$ and

$18.15^{0}$ . The sines of these angles are

$0.103,0.205$ and

$0.312$ which are in the ratio

$1:2:3$ . These peaks represent the first, second and third order reflection. The ratio confirms the correctness of Bragg's equation.
b) Preparation of colloids by chemical methods:
The chemical methods involve chemical reaction in a medium in which the dispersed phase is sparingly soluble. Some of the methods are

i) Double decomposition
An arsenic sulphide sol is prepared by passing a slow stream of hydrogen sulphide gas through a cold solution of arsenous oxide. This is continued till the yellow colour of the sol attains maximum intensity.

$As_{2}O_{3}+3H_{2}S\rightarrow As_{2}S_{3}+3H_{2}O$

$($ Yellow

$)$
Excess

$H_{2}S$ is removed by passing in a stream of hydrogen.
ii) Oxidation: A colloidal solution of sulphur is obtained by passing

$H_{2}S$ Into a solution of

$SO_{2}$

$2H_{2}S+SO_{2}\rightarrow 2H_{2}O+3S$
iii) Reduction: Silver sol and gold sol can be obtained by treating dilute solution, of silver nitrate or gold chloride with organic reducing agents like tannic acid or formaldehyde.

$AgNO^{3}+$ Tannic Acid

$\rightarrow AgSol$

$AuCl^{3}+$ Tannic Acid

$\rightarrow AuSol$
iv) Hydrolysis: Colloidal solutions of the hydroxides of

$Fe, Cr, Al$ etc. can be prepared by hydrolysis of their salts. A colloidal solution of ferric hydroxide is obtained by boiling a dilute solution of ferric chloride.

$FeCl_{3}+3H_{2}O\rightarrow Fe\left ( OH \right )_{3}+3HCl$

What is peptization? Explain.

Peptization refers to the formation of stable colloidal solution. A precipitate is converted into colloidal solution. This is achieved by shaking precipitate with dispersion medium in the presence of small amount of electrolyte.

Explain the mechanism of cleansing action of soaps.

A soap molecule consists of two parts:
A long chain hydrocarbon tail. It is hydrophobic in nature.
Head: It is hydrophilic in nature.
When soap is added to an oily or greasy part of cloth, the hydrocarbon part of soap dissolves in oil, keeping the head away from the oil. Big molecules of oil and soap break by rubbing into small emulsified oil droplets in water, which are washed away by stream of water. The soap molecules which form micelles assist in dissolving the dirt in water, thus, we can wash our clothes.

What is emulsifying agent? Give one example?

Emulsifying agent:
To prevent breaking of emulsions, a small amount of third substance called an emulsifying agent or emulsifier is added to the emulsion during its preparation. Usually, soaps, detergents, long chain sulphonic acids, lyophilic colloids, alkyl sulphates etc. are used as emulsifying agents. They form a protective layer surrounding the disperse phase and inhibits the particles to come closer and thus reduce the tendency of particles to coagulate. As an example, milk (an emulsion of liquid fats in water) is stabilized by casein (an emulsifying agent) which is a protein containing phosphate groups.

What is emulsion? How are emulsions classified? Give example?

Emulsion:
A colloidal system in which one liquid is dispersed in another liquid immiscible with it is called an emulsion.

The emulsions are classified into following two types.
(i) Emulsion of oil in water:
The disperse phase is an oil and the dispersion medium is water. For example, milk containing particles of liquid fat dispersed in water.
(ii) Emulsion of water in oil:
The disperse phase is water and the dispersion medium is an oil. For example, cod liver oil containing water particles dispersed in oil.

What are emulsions? How they are classified? Give one example of each.

An emulsion is a colloidal system in which one liquid is dispersed in another liquid immiscible with it.
There are two types of emulsions
(1) Emulsion of oil in water
An oil is disperse phase and water is dispersion medium. For example, milk consists of particles of liquid fat dispersed in water.
(2) Emulsion of water in oil
Water is disperse phase and an oil is dispersion medium. For example, cod-liver oil, containing particles of water dispersed in oil.

What is Emulsion?

An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable). Emulsions are part of a more general class of two-phase systems of matter called colloids. Although the terms colloid and emulsion are sometimes used interchangeably, emulsion should be used when both phases, dispersed and continuous, are liquids. In an emulsion, one liquid (the dispersed phase) is dispersed in the other (the continuous phase). Examples of emulsions include vinaigrettes, homogenized milk, mayonnaise, and some cutting fluids for metal working.

Write the chemical method by which $Fe(OH)_{3}$ sol is prepared from $FeCl_{3}$ .

Ferric hydroxide forms a hydrophobic sol. Hence it is prepared indirectly by the hydrolysis of ferric chloride with boiling water. The reaction takes place as follows:

$FeCl_3+3H_2O\rightarrow Fe(OH)_3+3HCl$

Draw a graph of potential energy v/s reaction coordinate showing the effect of a catalyst on activation energy.

The graph of potential energy v/s reaction coordinate showing the effect of a catalyst on activation energy is as shown. A catalyst provides an alternate pathway having lower activation energy.

What is Heterogeneous catalysis? Give an example.

The catalysis in which the catalyst and the reactants are present in different phases is called heterogeneous catalysis. A catalyst which exists in different phases from the reactants is known as heterogeneous catalyst.

Example: Hydrogenation of unsaturated compounds catalysed by finely divided metals like Ni, Pd, Pt.

$\displaystyle H_2C=CH_2(g) +H_2(g) \xrightarrow [or \: Ni]{Pt \: or \: Pd} H_3C-CH_3(g)$
Here catalyst is in solid phase whereas reactants and products are in gas phase.

Conversion of precipitate into colloidal solution is known as______.

Peptization is the process responsible for the formation of stable dispersion of colloidal particles in dispersion medium. In other words it may be defined as a process of converting a precipitate into colloidal sol by shaking it with dispersion medium in the presence of small amount of electrolyte. The electrolyte used in this process is called as peptizing agent.

This is particularly important in colloid chemistry or for precipitation reactions in an aqueous solution. When colloidal particles bear a same sign electric charge, they mutually repel each other and cannot aggregate together. Freshly precipitated aluminium or iron hydroxide is extremely difficult to filter because the very fine colloidal particles directly pass through a paper filter. To facilitate the filtration, the colloidal suspension must be first flocculated by adding a concentrated solution of salt to the system.

Catalysts which increase rate of a reaction are called ___________ catalyst.

Catalysts which increase rate of a reaction are called positive catalyst. Such catalyst provides an alternate pathway of lower activation energy.
Catalysts which decrease rate of a reaction are called negative catalyst.

Peptisation is a method of preparation of sols. Write a general procedure for peptization.

Peptization is the process responsible for the formation of stable dispersion of colloidal particles in dispersion medium.

In this method a precipitate is converted into colloidal sol by shaking it with dispersion medium in the presence of small amount of electrolyte. The electrolyte used in this process is called as peptizing agent.

What is peptization?

Explanation:

It is a method of producing stable colloids using an electrolyte.
Peptization utilizes the charge to produce colloids from the precipitate.
The electrolyte used in the process is called a peptizing agent.
Peptization process for Iron hydroxide is shown as below;

Who used the word 'catalyst' for the first time?

Jöns Jacob Berzellious (Swedish chemists ) used the word 'catalyst' for the first time. He invented catalysis.

For the coagulation of $100mL$ of arsenious sulphide solution, $5mL$ of $1M$ $NaCl$ is required. What is the coagulating power of $NaCl$ ?

Total volume after addition of

$5mL$ of

$1M$

$NaCl$ solution

$=105mL$
Thus,

$105\times$ molarity of

$NaCl$ in colloidal solution =

$5\times 1$
Molarity of

$NaCl$ in colloidal solution

$=\cfrac { 5 }{ 105 }$
Concentration in millimole

$=\cfrac { 5 }{ 105 } \times 100$

$=47.6$

Match the terms in List 1 with those of List 2.

1	Colloidal sol of graphite is Oil dag.
2	Detergent is Emulsifier as well as Collidal electrolyte.
3	Cellophane is a type of Xerogel.
4	Dextrin is a type of Emulsifier.

Match the phenomena in Column-I with example in Column-II:
Column-I
Column-II
(a) Persorption (p) $H_2$ on Ni surface
(b) Sorption (q) $CH_3OH$ in chabazite
(c) Negative adsorption (r) $NH_3 \,in\, H_2O$
(d) Occlusion (s) Dil. NaCl on blood charcoal

1546179_664649_ans_a49f62368c9c4259a368be116cc8e77f.jpg

Define Semipermeable membrane.

The membrane which allows the solvent molecules, but not the solute molecules, to pass through it is called semipermeable membrane. Cellulose, cellulose nitrate, animal bladder, etc can be used as semipermeable membranes.

What is a catalyst? give one example.

A catalyst is substance i.e a element or a compound that increases the rate of chemical reaction.

Examples:

1) Nickel, Ni is used in hydrogenation of palm oil into margarine.

2) Iron, Fe is used in Haber process. (Manufacturing of ammonia)

What is scum and how is it formed?

When a soap is used in hard water, a solid substance we call scum forms. This is because charged calcium and magnesium particles (called ions ) present in the water react with soap to form an insoluble substance.Scum builds up on clothes, baths and sinks. Detergents do not form scum.

What are the causes of Peptization?

As electrolyte is added to a freshly precipitated substance, the particles of the precipitate preferentially adsorbs one particular type of ions of the electrolyte. As a result they get dispersed due to electrostatic repulsions. This gives the particles of colloidal size.

526.3 mL of 0.5 M HCI is shaken with 0.5 g of activated charcoal and filtered. The concentration of the filtrate is reduced to 0.4M. What is the amount of adsorption (x/M)?

$n_i = 0.5 \times 526.3\ ml \times 10^{-3}$

$n_f = 0.4 \times 526.3\ ml \times 10^{-3}$

$\therefore \Delta n = 0.1 \times 526.3\ ml \times 10^{-3}$

$= 52.63\ mol \times 10^{-3}$

$\therefore ads./g = \dfrac{52.63 \times 10^{-3}}{0.5}$

$= 0.10526\ mol /g$

What are emulsions ? Give examples

The emulsion is a colloidal solution two or more liquid.

Two liquids can form different type of emulsion.

Ex :- Oil in water --- Oil in water emulsion.

Oil is depressed phase and water is dispersed medium.

Choose the correct set of identifications for the reaction
$Substrate(S) \longrightarrow Product (P)$
Whose mechanism is
$E+S \rightleftharpoons ES$
$ES \rightleftharpoons EP$
$EP \rightleftharpoons E+ P$

1352116_1138453_ans_4fff50ec584b487f926dc7f77feb46da.jpg

Name the catalyst used in contact process.

Catalyst used in contact process is vanadium pentoxide

$(V_2O_5)$

process:

(i)Burning of sulphur sulphide in air to greater

$SO_2$

(ii)Conversion of

$SO_2$ to

$SO_3$ by the reaction with oxygen in the presence of

$V_2O_5$

(iii)Absorption of

$SO_3$ in

$H_2SO_4$ to give oleum

$(H_2S_2O_7)$

Name the catalyst generally used in the hydrogenation of oils.

Nickel is the catalyst generally used in the hydrogenation of oil.

The nickel increases the rate of reaction of hydrogenation of oil by decreasing activation energy.

Based on the type of dispersed phase,what type of colloids are micelles?

Micelles are associated collides. Micelles are basically aggregate molecules which are present in a colloidal solution.

A typical micelle in aq solution forms an aggregate with a hydrophilic regions in contact with surrounding solvent. They are spherical in shape.

Why does physisorption decrease with the increase of temperature?

Physisorption is exothermic in nature. Therefore in accordance with the Le-Chatelier principle, it decreases with an increase in temperature. This means physisorption occurs at a low temperature more readily.

Physisorption is reversible in nature.

Give an example of a liquid in liquid type solution.

1375558_1227999_ans_480d5e7590da4c24a79dfbc5cdcc73c0.jpg

50 ml of 1 M oxalic acid (mol. wt. =126) is shaken with 0.5 g of wood charcoal. The final concentration of solution after adsoption is 0.5 M. Calculate the amount of oxalic acid adsorbed per gram of charcoal.

Amount of oxalic acid present $=(-50$ $mL\times 1$ $M)\times 10^{-3}$ $moles=5\times 10^{-2}$ $moles$ Number of moles absorbed $=(50\times 0.5)\times 10^{-3}$ $moles=25\times 10^{-3}=2.5\times 10^{-2}$ $moles$ Mass of oxalic acid absorbed $=(2.5\times 10^{-2})\times 126=315\times 10^{-2}=3.15$ $gm$

$3.15$ $gm$ oxalic acid $-0.5$ $g$ char coal.

$6.3$ $gm$ oxalic acid absorbed $-1$ $g$ charcoal.

Explain the preparation of Gold Sol by Bredig's arc method ?

Bredig's arc method consists of both dispersion and condensation.

An arc is struck between electrodes, under the surface of water containing some stabilizing agent such as traces of KOH (potassium hydroxide).

The intense heat of the arc vaporizes (Dispersion) some of the metal which then condenses under cold water. The water is kept cold as an ice bath

On increasing the temperature, the solubility of the solute in the solvent________.

Increases

Explain Adsorption theory of Heterogeneous Catalysis.

Adsorption theory of Heterogeneous Catalysis :

1. The reactants diffuse to the surface of the catalysts. In this process, the reactants first get in contact with the external surface out of which some of them get enter into interior through the cracks on the external surface.

2. These molecules then get adhered to the suitable sites available for adsorption.

3. The reactants, when bound to the surface have a higher probability of reacting with each other, and after the reaction, they form an intermediate compound.

4. After this process, the intermediate compound gets desorbed from the surface, which again becomes available for adsorption for other molecules to come.

5. The intermediate compound then disintegrates to form the final products, which then diffuse out of the internal pores and the external surface of the catalyst.

Define Adsorption theory of Heterogeneous Catalysis.

The modern adsorption theory is a combination of the old theory of adsorption and the intermediate theory of compound formation, the process of heterogeneous catalysis takes place in five steps-

The reactants diffuse to the surface of the catalysts.

These molecules then get adhered to the suitable sites available for adsorption.

The reactants, when bound to the surface have a higher probability of reacting with each other, and after the reaction, they form an intermediate compound.

The intermediate compound gets desorbed from the surface, which again becomes available for adsorption for other molecules to come.

The intermediate compound then disintegrates to form the final products, which then diffuse out of the internal pores and the external surface of the catalyst.

What is the role of promoters and poisons in catalysis?

Promoter increases the activity of catalyst and poison decreases the activity of catalyst.

For example:

In the formation of ammonia along with finely divided Fe as a catalyst we also use Mn as a promoter.

$N_2+3H_2\xrightarrow{Fe/Mn} 2NH_3$

What is observed when an emulsion is centrifuged?

When an emulsion is centrifuged, it breaks into constituent liquids, i.e., demulsification takes place.

In the reaction below the substance acting as a catalyst : -
${ 2KCIO }_{ 3 }\rightarrow 2KCI+{ 3O }_{ 2 }$

1358115_1560895_ans_ddc6566948d0494ab3117a364c260a03.jpg

Classify into alkanes, alkenes and alkynes :
Ethane, ethene, methane, ethyne, propene, propyne

$Alkanes$ -Ethane,Methane,

$Alkenes$ -Ethene, Propene

$Alkynes$ -Ethyne, Propyne

Name the structure shown in the figure. Also label $1$ and $2$

It is a structure of Micelle. The water-loving (hydrophilic) part of the soap molecules sticks to the water and points outwards, forming the outer surface of the micelle. The oil-loving (hydrophobic) parts stick to the oil and trap oil in the center where it can't come into contact with the water.

What are Emulsions? How are they classified?

Emulsion

$\rightarrow$ The colloidal solution in which both the dispersed phase and dispersion medium are liquids is called an emulsion.

Emulsions are classified as-

Oil in water type- The emulsion in which oil is present as the dispersed phase and water as the dispersion medium (continuous phase) is called an oil-in-water emulsion

E.g.- Milk is an example of the oil-in-water type of emulsion.

Water in oil type- The emulsion in which water forms the dispersed phase, and the oil acts as the dispersion medium is called a water-in-oil emulsion.

E.g.- Butter is an example of the water-in-oil type of emulsion.

(a) Explain the process of preparation of soap in laboratory.
(b) Why is common salt (sodium chloride) added during the preparation of soap?
(c) Why is soap not suitable for washing clothes when the water is hard?

(a) Soap can be prepared in the laboratory as follows:
1. Take about

$20\ ml$ of castor oil (cottonseed oil, linseed oil or soya bean oil) in a beaker.
2. Add

$30\ ml$ of

$20\%$ sodium hydroxide solution to it.
3. Heat the mixture with constant stirring till a paste of soap is formed.
4. Then add

$5$ to

$10$ grams of common salt (sodium chloride).
5. Stir the mixture well and allow it to cool. On cooling the solution, solid soap separates out.
6. When the soap sets, it can be cut into pieces called 'soap bars'.

(b) Common salt is added to the mixture to make the soap come out of solution. Though most of the soap separates out on its own some of it remains in solution/ Common salt is added to precipitate out all the soap from the aqueous solution.

(c) When soap is used for washing clothes with hard water, a large amount of soap in water is reacting with the calcium and magnesium ions of hard water to form an insoluble precipitate called a scrum, before it can be used for the real purpose of washing.

Define the following term:
Emulsifying agents

Emulsifying agents are those which acts as a stabilizer for emulsions and they prevents liquids from mixing.

(a) What is a soap? Name one soap.
(b) Describe the structure of a soap molecule with the help of a diagram.
(c) Explain the cleansing action of soap. Draw diagrams to illustrate your answer.

(a) A soap is the sodium salt (or potassium salt) of a long chain carboxylic acid (fatty acid) which has cleansing properties in water.
Example : Sodium stearate,

$C_{17}H_{35}COO^{-}Na^{+}$

(b) A soap molecule has two parts: the long-chain organic part and the ionic part containing the

$-COO^{-}Na^{+}$ group. It has to be remembered that this is not an ion, the atoms are all covalently bonded, the electrical charges show how the charges get polarized in the group. A soap molecule has a tadpole-like structure.

Polar end (end with sodium or potassium ion) of soap is hydrophilic (attracted towards the r) and the non-polar end (the hydrocarbon part) is hydrophobic (attracted towards hydrocarbons).

On dissolution in water, the hydrophobic ends attach themselves to dirt and remove it from the cloth.

Soap molecules form micelle and trap the dirt at the centre of the cluster. They remain suspended in water like particles of colloidal solution. The trapped dust particles are easily rinsed away with water.

1574427_1750948_ans_f080cf23f1cd47f1a503677c436e310a.png

(a) How is ethanoic acid obtained from ethanol? Write down the chemical equation of the reaction involved.
(b) How would you distinguish between ethanol and ethanoic acid by chemical test?
(c) Explain the formation of scum when hard water is treated with soap.

(a) Ethanoic acid is obtained from ethanol by the means of

$\textbf{oxidation reaction}$ . When ethanol is heated with alkaline potassium permanganate solution (or acidified potassium dichromates solution), it gets oxidised to ethanoic acid. It is called an oxidation reaction because oxygen is added to it during this conversion.

$CH_3CH_2OH(l) + 2[O]\xrightarrow[{Alkaline\ KMnO_4;\ Heat}]{or\ acidified\ K_2Cr_2O_7} CH_3COOH(l) + H_2O(l)$

(b)

$\textbf{Litmus test }$ : Some blue litmus solution is added to the organic compound (to be tested). If the blue litmus solution turns red, it shows that the organic compound is acidic in nature and hence it is a carboxylic acid (Ethanoic acid). Ethanol has no effect on any litmus solution.

(c) When soap is used for washing clothes with hard water, a large amount of soap in water reacts with the Calcium and Magnesium ions of hard water to form an insoluble precipitate called scum. This makes the cleaning of clothes difficult.

Give only the machanism of cleansing action of soaps.

Soaps are sodium or potassium salts of long-chain carboxylic acids. They contain two ends having different properties: the carboxylic acid part which is hydrophobic and the ionic end

$(Na^{+}or K^{+})$ which is hydrophilic.

The structure of the soap molecule is shown above in the image.

Dirt present in cloths in basically a hydrocarbon. When soap is used in water , the soap molecules tend to surround the dirt such that they form a cluster in which the hydrophobic tails are in the interior of the cluster and the hydrophilic part is on the surface of the cluster (see figure below). The hydrophilic part dissolves in water and the hydrophobic part dissolves in the hydrocarbon (dirt). This formation or cluster is called micelle.

$\text {Formation of micelle-}$

Agitating the water by hand or brush forces the hydrophilic end to move along the direction of agitation of the water, dragging the micelle holding the dirt out of clothes, and the dirt is rinsed away. In short, the cleansing action of soap is achieved by the formation of micelles.

1623437_1772561_ans_e075665f8e29470a8b114125e1e5e78f.png

Complete the following with appropriate reagent :

The complete reaction for conversion is shown above.

So, the reagent used for above conversion is

$\mathrm{CHCl_3 \ \ \& \ \ NaOH}$ .

1785453_1769672_ans_d468fd5c1f0341c2ba4ebf7320636e3b.png

Answer the following question.
Out of silica gel and anhydrous $CaCl_{2}$ , which will adsorb the water vapours?

Silica gel will adsorb the water vapours.

Match the columns

1692544_1767741_ans_efafbba92fed4515b16bdf10b6435051.png

How are emulsions different from Gels ? Give one example of each.

Emulsions are colloids where both dispersed phase and dispersing phase are liquid. In case of gels dispersed phase is liquid and dispersing medium is solid.
Example of emulsion is milk and example of gel is jelly.

How are the following collodial solutions prepared?
i. Sulphur in water
ii. Gold in water.

i. Sulphur sol is prepared by the oxidation of

$H_{2}S$ with

$SO_{2}$

$SO_{2} + 2H_{2}S \xrightarrow {Oxidation} 3S (Sol) + 2H_{2}O$

ii. Gold sol is prepared by the reduction of

$AuCl_{3}$ with formaldehyde.

$2AuCl_{3} + 3HCHO + 3H_{2}O \xrightarrow {Reduction} 2Au (Sol) + 3HCOOH + 6HCl$ .

Answer the following questions.
What happens when a freshly precipitated $Fe(OH)_{3}$ is shaken with water containing a small quantity of $FeCl_{3}$ ?

When a freshly precipitated

$Fe(OH)_{3}$ is shaken with water containing a small quantity of

$FeCl_{3}$ it is converted into the colloidal state.

$Fe(OH)_{3} + FeCl_{3} \rightarrow [Fe(OH)_{3}Fe]^{3+} + 3Cl^{-}$ .

What is the role of diffusion in heterogeneous catalysis?

The gaseous molecules diffuse on to the surface of the solid catalyst and get adsorbed. After the required chemical changes the products diffuse away from the surface of the catalyst leaving the surface free for more reactant molecules to get adsorbed and undergo reaction.

Mention the use of colloids?

1. homogeneous state for practical applications.
2. Preparation of medicines
3. Photographic solutions
4. Preparation of dyes.

Explain what is observed when.
Silver nitrate solution is added to potassium iodide solution.

If silver nitrate solution is added to potassium iodide solution, the precipitated silver iodide adsorbs iodide ions from the dispersion medium and negatively charged colloidal solution results.

$AgI + \underset {(From\ dispersion\ medium)}{I^{-}} \rightarrow \underset {(Negatively\ charged\ Sol)}{AgI/ I^{-}}$ .

Explain the following observation:
Sun looks red at the time of setting.

At the time of setting, the sun is at horizon. The light emitted by the sun has to travel a relatively longer distance through the atmosphere. As a result, blue part of light is scattered away by the particulate in the atmosphere causing red part to be visible.

Complete the missing components/variables given as x in the following reaction:

$C a C O_{3} \stackrel{x}{\longrightarrow} C a O(s)+C O_{2}(g)$

$\rightarrow heat$

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

Define Adsorption

Adsorption is the property due to which a substance absorbs gases, liquids and solids on its surface.

Motor cars are coated with ......

Motor cars are coated with Automotive paint. As it protects the vehicle from corrosion, heat differences, bumps, stone-chips, UV-light, etc. It improves ease of application by making it easier for paints to stick to the surface.

Hence, the correct answer is Automotive paint.

How will you distinguish between dispersed phase and dispersion medium in an emulsion?

On adding dispersion medium, emulsions can be diluted to any extent. The dispersed phase forms a separate layer if added in excess.

Select the correct statements which are related to the influence of catalyst in a reversible reaction.
a. Forward reaction takes place when a catalyst is used in a reversible reaction, $h$ . Attains equilibrium faster,
c. Catalyst does not help to form more pro-duct
d. The catalyst increase the rates of both the forward and the backward reactions to the same extent.
e. Increase the speed of backward reaction.
f. Does not helps to produce more product.

Statements

b,c,db,c,d are correct.

Explain why finely divide substance is more effective adsorbent.

Adsorption is a surface phenomenon. The extent of depend on the surface area, therefore adsorption substance like charcoal, silica gel provide large surface area. Hence, finely divided substance behave as good adsorbent.

Why alum is used to prevent bleeding from wound of body?

Blood is colloidal solution of substance like albumin in water . It has negatively charged particles .The fresh solution of alum or ferric chloride is added on flowing blood which coagulates blood by

$Al^{3+} or Fe^{3+}$ ions and stop flow of blood.

Which type of colloid is cheese?

Cheese is a gel in which dispersed phase is liquid and dispersion medium is solid.

Which catalyst and promoter are used in Haber's process ?

Catalyst and promoter are used in Haber's are Fe and Mo respectively .

Write the name of catalysis which convert methanol into gasoline.

Zeolite catalyst ZSM -5 is used for converting methanol into gasoline.

What is purple of cassius ?

Purple of cassius is a purple pigment formed by the reaction of gold salts with tin (II) chloride. It has been used to impart red colouration as well as to presence of gold as a chemical test.

Define absorption.

When the phenomenon of adsorption and absorption take place simultaneously then the process is called absorption.

Write an example of each type of emulsion.

Oil in water(O/W) : Milk

Water in oil (W /O) : Butter.

Write one example of homogeneous and heterogeneous catalysis.

Example of homogeneous catalysis :

$2SO_{2 (g)} + O_{2(g)} \overset{NO_{(g)}}{\rightarrow} 2SO_{3(g)}$

Example of heterogeneous catalysis:

$N_{2(g)} + 3H_{(g)} \overset{Fe_{(s)}}{\rightarrow} 2NH_{3(g)}$

Give the reasons:

Alum purifies drinking water.

Impure water contains soil particles, bacteria etc. These particles are negatively charged. Alum is added in water to remove them Al ions present in alum precipitation impurities in water. Pure water is separated by decantation.

The volume of nitrogen gas $V_m$ (measured at S.T.P.) required to cover a sample of silica gel with a mono- molecular layer is $129 cm^3 g^{-1}$ of gel. Calculate the surface area per gram of the gel if each nitrogen molecule occupies $16.2 \times 10^{-20} m^2$ .

$22400 \, cm^3$ of

$N_2$ at S.T.P. contain

$= 6.022 \times 10^{23}$ molecules

$\therefore 129 cm^3$ of

$N_2$ at S.T.P. will contain

$= \dfrac{6.022 \times 10^{23} \times 129}{22400} = 3.468 \times 10^{21}$ molecules

Area occupied by a single molecule

$= 16.2 \times 10^{-20} m^2$

$\therefore$ Area occupied by

$3.468 \times 10^{21}$ molecules of

$N_2 = (16.2 \times 10^{-20}) \times (3.468 \times 10^{21}) m^2 = 561.8 m^2$

$\therefore$ Surface area per gram of gel

$= 561.8 m^2$ .

$SnO_2$ forms a positively charged colloidal sol in acidic medium and a negatively charged sol in the basic medium. Why? Explain.

$SnO_2$ is amphoteric in nature. It reacts with acid, e.g., with

$HCl$ to form

$SnCl_4$ in the solution, the common

$Sn^{4+}$ ions are adsorbed on the surface of

$SnO_2$ particles thereby giving them a positive charge.

$SnO_2 + 4 HCl \rightarrow SnCl_4 + 2 H_2O$

$SnO_2 + Sn^{4+} \rightarrow \underset{Positively \, charged \, colloidal \, particles}{[SnO_2] : Sn^{4+}}$

$SnO_2$ reacts with a base, e.g.,

$NaOH$ to form sodium stannate

$(Na_2SnO_3)$ in the solution. The stannate ions are absorbed on the surface of

$SnO_2$ particles giving them a negative charge.

$SnO_2 + 2 NaOH \rightarrow \underset{Sodium \, stannate}{Na_2 SnO_3} + H_2O$

$SnO_2 + SnO_3^{2-} \rightarrow \underset{Negatively \,charged \, colloidal \, particles}{[SnO_2] : SnO_3^{2-}}$

Match the following.

There are some substances which at low concentrations behave as normal strong electrolytes but at higher concentrations exhibit colloidal behaviour due to the formation of aggregated particles. The aggregated particles formed are called micelles. These are also known as associated colloids. The formation of micelles takes place only above a particular temperature called Kraft Temperature (Tk) and above a particular concentration called Critical Micelle Concentration (CMC).
The spontaneous liberation of liquid from a gel is called syneresis or weepingof gels. It is reverse of swelling.
For example : Gelatin, agar-agar show syneresis at low concentration while sillicic acid shows it at high concentration.
The separation of an emulsion into its constituent liquids is called demulsification. Various techniques employed for this are freezing, boiling, centrifugation, electrostatic precipitation or chemical methods which destroys the emulsifying agents.
The colloidal solution in which the particles ofthe dispersed phase have a great affinity (or love) for the dispersion medium, are called lyophilic colloids. These solutions are easily formed and the lyophilic colloids are reversible in nature. In case water acts as the dispersion medium, the lyophilic colloid is called hydrophilic colloid. The common examples of lyophilic colloids are glue, gelatin, starch, proteins, egg albumin, rubber, etc.
The colloidal solutions in which there is no affinity between particles of the dispersed phase and the dispersion medium are called lyophobic colloids. Such solutions are formed with difficulty only by special methods. These sols are readily precipitated(or coagulated) on the addition of small amounts of electrolytes, by heating or by shaking and hence are not stable. Further, once precipitated, they do not give back the colloidal sol by simple addition of the dispersion medium.Hence these sols are also called irreversible sols. They need stabilising agents for their preservation.

Distinguish between the meaning of the terms adsorption and absorption. Give one example of each.

During adsorption, the concentration of one substance on the surface of other substance is much higher than the concentration in the bulk. On the other hand, during absorption, there is uniform distribution of molecules of one substance throughout the body of other substance.
Thus, silica gel adsorbs water vapour while anhydrous calcium chloride absorbs water.

What are emulsions? What are their different types? Give examples of each type.

Emulsions are colloidal solutions with both dispersed phase and dispersion medium being liquid. Thus, finely divided droplets of one liquid are dispersed in another medium. Emulsions can be formed from any two immiscible liquids.

Two types of emulsions include oil in water emulsion and water in oil emulsion.

Oil in water emulsion :
The dispersed phase is oil. It is present in a small amount. The dispersion medium is water. It is present in a large amount.

For example, milk is an emulsion of soluble fats in water.

Water in oil emulsion :

The dispersed phase is water. It is present in a small amount. The dispersion medium is oil. It is present in large amount.

For example, butter is an emulsion of water in oil.

Action of soap is due to emulsification and micelle formation. Comment.

Soap molecules have two parts, on is polar head which is hydrophilic (water soluble) carboxylate group and other is non polar tail, which is hydrophobic (oil soluble) hydrocarbon tail. In water, several soap molecules aggregate to form micelles in which hydrocarbon tails are in the interior of cluster and polar heads are at the surface of clusters. The dirt in cloth is due to presence of dust particles in fat or grease which stick to the cloth. In the soap solution, micelles are formed around oil droplets. The hydrophobic part of soap is in the oil droplet and hydrophilic part projects outside like bristiles. The oil drops and micelle are then pulled in water due to hand rubbing or agitation and are washed away.

What role does adsorption play in heterogeneous catalysis?

Heterogeneous catalysis usually involves gaseous reactants and solid catalyst. Due to physisorption or chemisorption, the reactant molecules are adsorbed on the surface of the solid catalyst. This increases the reactant concentration on the catalyst surface and the rate of the reaction.

One of the reactant molecule fragments on catalyst surface and produces active sites which increase the rate of the reaction. The product molecules with no affinity for the adsorbent desorb and catalyst surface becomes free for adsorption of other catalyst molecules. This is in accordance with the adsorption theory.

How do emulsifying agents stabilise the emulsion?

Emulsifiers stabilize an emulsion by reducing the interfacial tension between two liquids forming the emulsion. Emulsifiers are long-chain molecules with polar groups.

For example, casein (milk protein) is an emulsifier. It forms a protective layer around fat molecules dispersed in water. This reduces interfacial tension and stabilizes the emulsion.

Another example includes soap as an emulsifying agent. Soap molecules form a protective film around each oil droplet. This reduces interfacial tension and stabilizes the emulsion.

Explain the cleaning action of soap. Why do soap not work in hard water?

A soap molecule has different polarities. At one end of it is the long hydrocarbon chain that is non-polar and hydrophobic, i.e. insoluble in water but soluble in oil. At the other end is the short polar carboxylate ion which is hydrophilic i.e.,soluble in water but insoluble in oil and grease.

When soap is shaken with water it becomes a soap solution that is colloidal in nature. Agitating of soap tends to concentrate the solution on the surface and causes foaming. This helps the soap molecules make a unimolecular film on the surface of water and to penetrate the fabric. The long non-polar end of a soap molecule that are hydrophobic, gravitate towards and surround the dirt (fat or oil with dust absorbed in it). The short polar end containing the carboxylate ion, face towards the water away from the dirt. A number of soap molecules surround or encircle dirt and grease in a clustered structure called 'micelles', which encircles such particles and emulsify them.

The subsequent mechanical action of rubbing or tumbling dislodges the dirt and grease from the fabric. These get detached and are washed away with excess of water leaving the fabric clean.

The cleaning action of soap is due to micelle formation and emulsion formation. Inside water a unique orientation forms clusters of molecules in which the hydrophobic tails are in the interior of the cluster and the ionic ends on the surface of cluster. This results in the formation of micelle. Soap in the form of micelle cleans the (dirt) oil as the oil will be collected at the centre of micelle. This property of soap makes it an emulsifier. The dirt suspended in micelles is easily rinsed away. This is known as cleaning action of soap.

Name the two groups into which phenomenon of catalysis can be divided. Give an example of each group with the chemical equation involved.

The two groups into which phenomenon of catalysis can be divided are:

(i) Homogeneous catalysis: When the reactants and the catalyst are in the same phase, the catalysis is said to be homogeneous catalysis.

For example,

$SO_{2}$ is oxidised to

$SO_{3}$ in the presence of nitric oxide,

$NO$ as catalyst.

$2SO_{2}(g) + O_{2}(g) \xrightarrow {NO(g)} 2SO_{3}(g)$

(ii) Heterogeneous catalysis: When the reactants are in a different phase than the catalyst, the catalysis is said to be heterogeneous.

For example, the combination of dinitrogen and dihydrogen to form ammonia in the presence of finely divided iron as a catalyst.

$N_{2}(g) + 3H_{2}(g) \xrightarrow {Fe(s)} 2NH_{3}(g)$ .

Give four examples of heterogeneous catalysis.

Examples of heterogeneous catalysis are as shown.
(1) Ammonia is manufactured from hydrogen and nitrogen in Haber's process. Finely divided iron catalyst is used.

$\displaystyle N_2(g) + 3H_2(g) \xrightarrow {Fe(s)} 2NH_3(g)$
Catalyst is in solid phase and the reactants are in gas phase.
(2) During manufacturing methanol from

$CO$ and hydrogen, a mixture of copper and zinc oxide is used as a catalyst and

$\displaystyle Cr_2O_3$ is used as promoter.

$\displaystyle CO(g) + 2H_2(g) \xrightarrow {Cu, ZnO, Cr_2O_3} CH_3OH(l)$
(3) In the contact's process for manufacturing

$\displaystyle SO_3$ from

$\displaystyle SO_2$ , platinised asbestos or

$\displaystyle V_2O_5$ is used as catalyst.

$\displaystyle 2SO_2 (g) + O_2 (g) \xrightarrow {Pt or V_2O_5} 2SO_3 (g)$
(4) Nickel catalyst is used for the dehydrogenation of ethanol.

$\displaystyle CH_3CH_2OH \xrightarrow {Ni} CH_3CHO + H_2$

Give four uses of emulsions.

The four uses of emulsions are as follows:

(1) Concentration of ores in metallurgy : Some oils (such as pine oil) are used in the froth floatation process for the concentration of sulphide ores of metals. Oil forms emulsion with ore particles. Air is bubbled through emulsion to raise it to the surface and skim it off.
(2) In medicine : Water in oil emulsions are used in several pharmaceuticals and cosmetics that are available in liquid form. Examples include cod-liver oil, B-complex, ointments etc.
(3) Cleansing action of soaps : Oil in water emulsion is the basis for the cleansing action of soaps.
(4) Milk : Milk is an emulsion of fat in water. It is an important constituent in our diet.

Explain the following giving a suitable example for each.
(i) Aerosol (ii) Emulsion (iii) Micelle

(i) An aerosol is a colloid in which dispersed phase is a solid and dispersion medium is a gas, eg., dust, smoke.

(ii) Emulsion is a colloid solution in which both the dispersed phase and dispersion medium are in liquid state, eg., milk and cod liver oil.

(iii) They are associated colloids showing colloidal behavior at high concentration and strong electrolytes as low concentration, eg., soap.

Draw the simple figure of a soap molecule.

Match the pairs (choose the correct answer from section 'B' for section 'A'):

Gold Solution is a Lyophobic colloid. There is no affinity between gold particles (dispersed phase) and the dispersion medium

Gold Number is used for Lyophillic colloids. It is defined as the minimum amount of protective colloid in milligrams which prevents a colour change from red to violet of 10 ml gold sol by the addition of 1 ml of 10% NaCl solution.

Coagulation Power is governed by Hardy-Schulze Rule. Greater is the valency of the oppositely charged ion of the electrolyte being added, the faster is the coagulation.

Physical Adsorption involves weak Van der Waals Forces of attraction.

Corrosion is an Electro-chemical phenomenon. It involves a redox reaction.

Write one difference in each of the following:
(a) Multimolecular colloid and Associated colloid
(b) Coagulation and Peptization
(c) Homogeneous catalysis and Heterogeneous catalysis

(a) Multimolecular colloids: It consists of aggregates of a large number of atoms or smaller molecules. Its size is in the range of 1-1000nm.

Associated colloids: At low concentration, they act as strong electrolytes whereas at high concentrations form aggregates or micelles

(b) Peptization can be defined as dispersing the precipitate into colloidal particles whereas Coagulation can be defined as colloidal particles join to form large-sized particles.

(c) In a heterogeneous reaction, the catalyst is in a different phase from the reactants. In a homogeneous reaction, the catalyst is in the same phase as the reactants.

a) Which types of an emulsion is 'vanishing cream'. Write its appropriate name.
b) Draw neat and labelled diagram of above emulsion.

'Vanishing cream' is a cream or ointment that leaves no visible trace when rubbed into the skin.
It is "oil in water" type emulsion. It contains potassium, ammonium, or sodium stearate with water and free stearic acid, a hygroscopic ingredient such as glycerol, and a small amount of a fatty ingredient.

What happens when an emulsion is centrifuged?

When an emulsion is centrifuged, the two components of emulsion (disperse phase and dispersion medium) will occur. Such process is carried out in ultracentrifuges having 15000 or more revolutions per minute.

What is peptisation? Give an example

Peptisation is the process of converting a precipitate into colloidal particles by adding suitable electrolyte. The electrolyte is known as peptising agent. It is stabilising agent.
For example, the addition of small amount of dil.

$HCl$ to stannic oxide precipitate gives a stable sol of stannic oxide.

Write the difference between absorption and adsorption.

Adsorption	Absorption
It is a surface phenomenon.	It is a bulk phenomenon.
The adsorbent surface retains excess concentration of the adsorbate.	The absorbent surface doe not retains excess concentration of the absorbate. There is uniform distribution of absorbate throughout the body of absorbent.
It is exothermic. Heat is evolved during process.	It is mostly endothermic process.
Initially the rate of adsorption is rapid but falls as the time passes.	The rate of absorption is uniform throughout.

Write short notes on Peptization.

The reaction between amine (

$NH_2$ ) and carboxyl (

$COOH$ ) group of two or more amino acids (same or different) results in the formation of amide linkage (

$-CO-NH-$ ), upon elimination of water molecule. This amide linkage is called peptide linkage and the product is called a peptide. This process is termed as peptization. Depending on the number of amino acids linked together such as 2, 3 or more, they are refered as dipeptide, tripeptide or polypeptides, respectively.

Write down the cleansing action of soap?

The cleansing action of soap depends on wetting action of soap and emulsification power and adsorption of grease and dirt particles.
Soap is rubbed on cloth. Soap emulsifies the grease. The grip of grease on dirt is loosened. The dirt is washed away.
A colloidal solution of soap in water is formed. It adsorbs dirt particles and removes them.

What is a protective colloid ?

Lyophilic sols are more stable than lyophobic sols. This is due to the
fact that lyophilic colloids are extensively solvated, i.e., colloidal particles
are covered by a sheath of the liquid in which they are dispersed.
Lyophilic colloids have a unique property of protecting lyophobic
colloids. When a lyophilic sol is added to the lyophobic sol, the lyophilic
particles form a layer around lyophobic particles and thus protect the
latter from electrolytes. Lyophilic colloids used for this purpose are
called protective colloids.

Write any two characteristics of Chemisorption.

$\bullet$ In Chemisorption, the gas molecules or atom are held to the solid surface by chemical bonds which can be both covalent or ionic.

$\bullet$ Chemisorption is irreversible in nature due to the formation of a surface compound by interaction with gas and solid surface.

Define adsorption with an example. Why is adsorption exothermic in nature? Write the types of adsorption based on the nature of forces between adsorbate and adsorbent.

The accumulation of the molecular species at the surface rather than in the bulk of a solid or liquid is known as adsorption. For example, water vapour are adsorbed by silica gel.

When a gas is absorbed on the surface of a solid its entropy decreases, i.e.,

$\Delta S$ become

$-ve$ . Since adsorption is a spontaneous process, therefore,

$\Delta G (= \Delta H - T\Delta S)$ must be negative. As

$-T\Delta S$ is

$+ve$ ,

$\Delta G$ can be negative only if

$\Delta H$ has sufficiently high

$-ve$ value. Hence, adsorption is exothermic in nature.

There are two types of adsorption based on the nature of forces between adsorbate and adsorbent.

i. Physical adsorption, when the accumulation of gas on the surface of a solid occurs due to weak van der Waal forces.

ii. Chemical adsorption, when the gas molecules or atoms are held to the surface of solid by chemical bonds.

Differentiate between homogeneous and heterogeneous catalysis with one example of each.

Homogeneous catalysis: catalysis in which the reactants and catalyst are in same phase.I.e same physical state.

Example: $2SO_2(g) + O_2(g)\overset{NO(gas)}{\rightarrow}2SO_3(g)$

Heterogeneous catalysis: catalysis in which the reactants and catalyst are in phases .Ie different physical states

Example: $2SO_(g) + O_(g)\overset{Pt(s)}{\rightarrow}2SO_3(g)$

What is the role of desorption in the process of catalysts?

Desorption makes the surface available again for fresh adsorption of reactant molecules.

What is an emulsion?

Emulsion is a colloidal solution in which both the dispersed phase and dispersion medium are liquids. Example: milk, cod liver oil, etc.

Match list I (Colloidal system) with List II (Example)

(A) Dextrin is an example of emulsifier.

(B) Foil of cellophane is an example Xerogel.

(D) Purple of cassius (gold sol) is colloidal solution.

Define the following term:
Protective colloid

Protective colloid are lyophilic colloid when present in small quantities keep lyophobic colloids from precipitating under the coagulating action of electrolytes.

Define desorption.

The process of removal of an adsorbed substance from a surface on which it is absorbed is called desorption.

What is physical adsorption?

If the adsorbate is held on an adsorbent surface by weak van der Waals' forces, the adsorption is called physical adsorption.

Match the columns

1692572_1767753_ans_521f1712981b4f379fe175cd98e9f9f4.png

What is sorption?

Sorption is the process in which adsorption and absorption take place simultaneously. Example: dyeing of cotton fibres by azo dyes.

Match the compounds in Column I with their characteristics/ tests/ reaction(s) / stereochemistry given in Column II. Matching can be more than one.

Why is desorption important for a substance to act as good catalyst?

After the completion of reaction between adsorbed reactants, the process of desorption is important to remove products and further create space for the other reactant molecules to approach the surface and react. So, desorption is important for a substance to act as a good catalyst.

How does a catalyst work?

Catalysts provide an alternate path involving lower activation energy for the reactants.

Answer the following questions.
How does $BF_{3}$ act as a catalyst in industrial process?

$BF_{3}$ acts as a catalyst in the industrial process because

$BF_{3}$ is an electron-deficient compound and helps to generate electrophile.

Answer the following questions.
Why is a finely divided substance more effective as an adsorbent?

Powdered or finely divided substances have greater surface area as compared to their crystalline forms. Greater the surface area, greater is the adsorption.

Give reasons:
Gelatin which is a peptide is added in ice-creams.

Ice-creams are emulsions that get stabilised by emulsifying agents like gelatin. So, gelatin which is a peptide is added in ice-creams.

Indicate a chemical reaction involving a homogeneous catalyst.

$2SO_{2}(g) + O_{2}(g) \xrightarrow {NO(g)} 2SO_{3}(g)$ . Here,

$NO$ is the catalyst.

How will you distinguish between dispersed phase and dispersion medium in an emulsion?

On adding dispersion medium, emulsions can be diluted to any extent. The disperse phase forms a separate layer if added in excess.

A colloidal solution of ferric oxide is prepared by two different methods as shown below. [HOTS]
i. What is the charge on colloidal particles in two test tubes $(A)$ and $(B)$ ?
ii. Give reasons for the origin of charge.

i. Colloidal particles of test tube

$(A)$ are positively charged whereas colloidal particles of test tube

$(B)$ are negatively charged.

ii. In test tube

$(A), Fe^{3+}$ is adsorbed on the precipitate

$Fe_{2}O_{3} . xH_{2}O$ [or

$Fe_{2}O_{3} . xH_{2}O/ Fe^{3+}$ is formed].

In test tube

$(B), OH^{-}$ ion is adsorbed on the precipitate

$Fe_{2}O_{3} . xH_{2}O$ [or

$Fe_{2}O_{3} . xH_{2}O/ OH^{-}$ is formed].

Write two difference between sols and emulsions.

Two differences between sols and emulsions are:

(i) Sols are dispersion of solids in liquids while emulsions are dispersions of liquids in liquids.

(ii) Sols are quite stable whereas emulsions are less stable.

A colloidal solution of $AgI$ is prepared by two different methods as shown in figure below.
i. What is the charge of $AgI$ colloidal particles in the two test tubes $(A)$ and $(B)$ ?
ii. Give reasons for the origin of charge.

i. Test tube

$(A)$ has negative charge whereas test tube

$(B)$ has positive charge on the colloidal particles.

ii. In test tube

$(A), I^{-}$ is adsorbed on precipitate

$AgI$ [or

$AgI/ I^{-}$ is formed] and in test tube

$(B), Ag^{+}$ is adsorbed on precipitate

$AgI$ [or

$AgI/ Ag^{+}$ is formed].

Answer the following questions.
Differentiate between adsorption and absorption.

Sl. no.	Adsorption	Absorption
i.	It is a surface phenomenon. Adsorbate molecules are held at the surface of adsorbent.	Absorption occurs in the bulk of absorbing substances.
ii.	The concentration of the adsorbate at the adsorbent surface is much more than that in the bulk.	Absorbed material is uniformly distributed throughout the bulk. Thus, concentration is same throughout.
iii.	Initially, the rate of adsorption is rapid. It decreases slowly till equilibrium is attained. Example: Water vapours on silica gel.	Absorption occurs with a uniform rate. Example: Water vapours are absorbed by anhydrous $CaCl_{2}$ .

Give reasons for the following:
Rough surface of catalyst is more effective than smooth surface.

Rough surface of a catalyst provides more surface area of adsorption.

Answer the following questions.
Heterogeneous catalysis.

Heterogeneous catalysis: There are many gaseous reactions of industrial importance involving solid catalyst. Manufacture of ammonia using iron as a catalyst, manufacture of

$H_{2}SO_{4}$ by contact process using

$V_{2}O_{5}$ catalyst and use of finely divided nickel in the hydrogenation of vegetable oils are the excellent examples.

The gaseous reactants are adsorbed on the surface of the solid catalyst. As a result, the concentration of the reactants increases on the surface of the catalyst and hence the rate of reaction increases. Since the reactants are gases and catalyst are solid so these are heterogeneous catalysis.

Define the following terms:
Homogeneous catalysis.

In a catalysis process, if the catalyst and the reactants are in the same phase (liquid or gas), the process is said to be homogeneous catalysis. For example, oxidation of

$SO_{2}$ to

$SO_{3}$ with

$O_{2}$ in the presence of

$NO$ as a catalyst.

$2SO_{2}(g) + O_{2}(g) \xrightarrow {NO(g)} 2SO_{3}(g)$ .

How does a solid catalyst enhance the rate of combination of gaseous molecules?

When gaseous molecules come in contact with the surface of a solid catalyst, adsorption of gaseous molecules takes place at the surface of the catalyst. It increases the concentration of reactants on the surface. Different molecules adsorbed side by side have better chance to react and form new molecules. This enhances the rate of adsorption is utilised in enhancing the reaction rate.

What type of collodial sols are formed in the following:
i. Sulphur vapours are passed through cold water.
ii. White of an egg is mixed with water.
iii. Soap solution.

i. Multimolecular because sulphur molecules associate together to form multimolecular colloids.

ii. Macromolecular because protein molecules present in the white of the egg are macromolecules soluble in water.

iii. Associated because

$RCOO^{-}$ ions associate together to form micelles.

Give reasons for the following:
Smoke passed through charged plates before allowing it to come out of chimneys in factories.

Smoke is passed through charged plates so that unburnt charged carbon particles get settled between the charged plate leaving behind air free from pullutants.

What happens when a freshly precipitated $Fe(OH)_{3}$ is shaken with a little amount of dilute solution of $FeCl_{3}$ ?

It is converted into the colloidal state by preferential adsorption of

$Fe^{3+}$ ions.

$Fe(OH)_{3} + FeCl_{3} \rightarrow \underset {Reddish\ brown\ coloured\ colloid}{[Fe(OH)_{3}]Fe^{3+}} + 3Cl^{-}$ .

$SnO_{2}$ forms a positively charged colloidal sol in acidic medium and a negatively charged sol in the basic medium. Why? Explain.

$SnO_{2}$ is amphoteric in nature. It reacts with acids such as

$HCl$ , to form

$SnCl_{4}$ in the solution. The common

$Sn^{4+}$ ions are adsorbed on the surface of

$SnO_{2}$ particles to give a positively charged colloidal sol.

$SnO_{2} + 4HCl \rightarrow SnCl_{4} + 2H_{2}O$

$SnO_{2} + Sn^{4+} \rightarrow \underset {Positively\ charged\ sol}{(SnO_{2}) : Sn^{4+}}$

$SnO_{2}$ is amphoteric in nature. It reacts with a base such as

$HCl$ , to form

$Na_2SnO_3$ in the solution. The

$SnO_3^{2-}$ ions are adsorbed on the surface of

$SnO_{2}$ particles to give a negatively charged colloidal sol.

$SnO_{2} + 2NaOH \rightarrow \underset {Sodium\ stannate}{Na_{2}SnO_{3}} + H_{2}O$

$SnO_{2} + SnO_{3}^{2-} \rightarrow \underset {Negatively\ charged\ sol}{(SnO_{2}) : SnO_{3}^{2-}}$ .

Write one difference in each of the following:
Homogeneous catalysis and Heterogeneous catalysis.

Sl. no.	Homogeneous catalysis	Heterogeneous catalysis
i.	Reactants and catalyst are in the same phase.	Reactants and catalyst are not in the same phase.
ii.	$2SO_{2}(g) + O_{2}(g)\xrightarrow {NO(g)} 2SO_{3}(g)$	$N_{2}(g) + 3H_{2}(g) \xrightarrow {Fe(s)} 2NH_{3} (g)$

Match the items of Column I and Column II.

(i) Dialysis: Process used for the purification of colloid.

(ii)Peptization: Peptisation may be defined as the process of converting a precipitate into a colloidal sol by shaking it with dispersion medium in the presence of a small amount of electrolyte.

(iii) Emulsification: Process of the cleansing of oil and dirt from soap by
emulsification.

(iv) Electrophoresis: The movement of colloidal particles under an applied electric potential is called electrophoresis.

Hence,

A matches with 4

B matches with 3

C matches with 1

D matches with 2

Give two examples of emulsifying agents for $O/W$ and $W/O$ type of emulsions.

Emulsions are liquid-liquid colloidal systems i.e. the dispersion of finely divided droplets in another liquid. Generally, one of the two liquids is water. There are two types of emulsions:-

(i) Oil dispersed in water type (o/w) (ii) water dispersed in oil type (w/o)

Emulsions of oil in water are unstable and sometimes they separate into two layers on standing. For stabilization of an emulsion, a third component called emulsifying agent is added.

Principal emulsifying agents for o/w emulsions are proteins, gums, synthetic soaps etc and for w/o emulsions, heavy metal salts of fatty acids, long-chain alcohols etc.

Both soap and detergent are some type of salts. what is the difference between them Describe in brief the cleansing action of soap. why do soaps not form lather in hard water List two problems that arise due to the use of detergents instead of soaps.

Soaps are sodium or potassium salts of long-chain carboxylic acids. Detergents are generally ammonium or sulphate salts of long chain carboxylic acids.
For cleansing action of soaps, Soaps do not form lather in hard water because hard water contains calcium and magnesium salts. Soap molecules react with calcium and magnesium salts to form an insoluble precipitate called scum.
Two problems which arise because of the use of detergents are:
Detergents are non-biodegradable; hence, detergents accumulate in the enviorment and cause problems.
Certain phosphate additives are added to detergents which form a thick green scum over the river water and harm the animal life in the river.

What is the function of catalyst in a chemical reaction?

Catalyst alters the speed of a chemical reaction.

Name the catalyst which facilitates change of vegetable oil to vegetable ghee.

Hydrogenation is the process of converting vegetable oil to vegetable ghee.

During hydrogenation, vegetable oils are reacted with hydrogen gas at about 60°C. A

$Nickel$ catalyst is used to speed up the reaction.

Differentiate between following :
Catalyst promoter and catalyst poison.

A catalyst promoter increases the efficiency of a catalyst, but a catalyst poison suppresses the function of the catalyst.

Explain different types of catalyst.

On the basis of physical state

Homogeneous Catalyst: When the catalyst, reactants, and products all are in the same physical state.

Example:

$2SO_2(g)+O_2(g)\xrightarrow []{NO(g)} 2SO_3(g)$

Heterogeneous Catalyst: When the catalyst, reactants, and products are in different physical states.

Examples:

$N_2(g)+3H_2(g)\xrightarrow []{Fe(s)}2NH_3(g)$

On the basis of action:

Positive catalyst: When catalyst enhances the speed of reaction

Example :

$2KClO_3\xrightarrow [\Delta]{MnO_2}2KCl+3O_2$

Negative catalyst: When catalyst reduces the speed of reaction.

Example

$2H_2 O_2 \xrightarrow []{glycerol} 2H_2O +O_2$

What do you know about types of catalyst and about characteristics of catalyst?

Following are different types of catalyst:

1) Homogeneous Catalyst: When the catalyst, reactants and products, all are in the same physical state, the catalyst is called homogenous catalyst.

$CH_3COOCH_3(l)+H_2O (l) \xrightarrow []{HCl(aq)}CH_3COOH (aq)+CH_3OH(aq)$

$2SO_2(g)+O_2(g) \xrightarrow []{NO(g)}2SO_3 (g)$

2) Heterogenous catalyst: When catalyst, reactants and products are in different physical states, the catalyst is called hetereogenous catalyst.

Following are some example of heterogeneous catalyst.

$N_2(g) +3H_2 (g) \xrightarrow []{Fe(s)}2NH_3 (g)$

Vegetable oil

$(l)+H_2(g)\xrightarrow []{Ni(s)}$ vegetable ghee

$(s)$

Moreover, catalysts are categorized on other criteria as well. Other types are : slow catalyst, fast catalyst, auto-catalyst, bio-catalyst, etc.

On the basis of action

1) Positive catalyst: When catalyst enhances the speed of reaction.

Example

$2KClO_3 \xrightarrow [\Delta]{MnO_2}2KCl+3O_2$

2) Negative catalyst: When catalyst reduces the speed of reaction:

Example:

$2H_2O_2 \xrightarrow []{glycerol}2H_2O+O_2$

Characteristics of catalyst:

A) Catalyst only alter the speed of a reaction but never participates in the reaction.

B) A minute quantity of catalyst is enough.

C) Each reaction has a specific catalyst and a catalyst cannot work for all reactions.

D) Catalyst doesn't initiate a reaction.

E) Catalyst has same action on forward reaction and backward reaction.

Mention the dispersed phase and dispersion medium present in the following colloids
(A) Paint (B) Froths of air

A colloid is a heterogeneous system in which one substance is dispersed (dispersed phase) as very fine particles in another substance called dispersion medium.

Depending upon whether the dispersed phase and the dispersion medium are solids, liquids or gases, different colloidal systems are possible.

A) Paint -

Type of colloid

$\rightarrow$ sol

Dispersed phase

$\rightarrow$ solid

Dispersion medium

$\rightarrow$ liquid

B) Froths of air -

Dispersed phase

$\rightarrow$ Gas

Dispersion medium

$\rightarrow$ liquid

Type of colloid

$\rightarrow$ foam

Write short notes of Catalytic poison. Give example.

Catalytic poisons are those substances which inhibit or distroy the activity of the catalyst by their presence.

Example :-

1) The platinum catalyst used in the oxidation of hydrogen is poisoned by CO.

2) The activity of Iron catalyst is distroyed by the presence of

$H_2S$ or

$CO$ in synthesis of ammonia by Haber's process.

3) The presence of traces of

$AS_2O_3$ in the reacting gases reduces the activity of platinized asbestos which is used as catalyst in manufacture of

$H_2SO_4$ in contact process.

What are Catalyst?

$Catalyst$ is a substance which does not take part in chemical reaction, but change the rate of a reaction.

What is the purpose of catalyst promoter and catalyst poison?

Catalyst promoter enhances the action of a catalyst, while catalyst poison supresses the action of a catalyst.

Name different types of catalyst.

Homogeneous catalyst, heterogeneous catalyst, positive catalyst, negative catalyst, autocatalyst, bio-catalyst.

Auto catalyst: When product of the reaction enhances the speed of the reaction.

Example :

$CH_3COOC_2H_5+H_3O^+\to CH_3COOH+C_2H_5OH$

Bio-catalyst : Substance that catalyze biochemical reaction.

Example: Maltose

$\xrightarrow []{Maltase}$ Glucose

It is found that when litmus is shaken with animal charcoal adsorption takes place.

Find out the adsorbent and adsorbate in this process.

Litmus is the adsorbate and charcoal is the adsorbent.

Classify the following into homogenous and heterogenous catalysis
Hydrolysis of an organic ester

$CH_{3}COOC_{2}H_{5}(aq)+H_{2}O(l)\overset{H^+(aq)}{\rightarrow}CH_3COOH(aq)+C_{2}H_{5}OH(aq)$

: Homogeneous catalysis

It is found that when Litmus is shaken with animal charcoal adsorption takes place
explain the terms adsorbent and adsorbate.

The material providing the surface upon which adsorption occurs, is known as the adsorbent and substance adsorbed is called adsorbate.

Classify the following into homogenous and heterogenous catalysis
Catalytic decomposition of ozone by chlorine

$2O_{3}(g)\overset{Cl_2({g})}{\longrightarrow}3O_{2}(g)$

Homogeneous catalysis

What are emulsions? What are their different types? Give example of each type.

The colloidal solution in which the dispersed phase and dispersion medium are liquids is called an emulsion.

There are two types of emulsion:

1) Oil in water type:

Here, oil is the dispersed phase while water is the dispersion medium. For example milk, vanishing cream, etc.

2) Water in oil type:

Here, water is the dispersed phase while oil is the dispersion medium. For example cold cream, butter, etc.

Give reason why a finely divided substance is more effective as an adsorbent.

Adsorption is a surface phenomenon. Therefore, adsorption is directly proportional to the surface area. A finely divided substance has a large surface area. Both physiorption and chemisorption increase with an increase in the surface area. Hence, a finely divided substance behaves as a good absorbent.

Differentiate between following :
Homogeneous and heterogeneous catalysts.

When physical state of catalyst, reactants and products is same, it is a homogeneous catalyst.

When physical states of catalyst, reactants and products are different, it is a heterogeneous catalyst.

What is Colloid?

A colloid is a heterogeneous mixture in which size is too small to be individually seen by naked eyes.

Explain the cleansing action of soaps and detergents with the help of micelle formation.

Soaps and detergents consist of a large hydrocarbon tail with negatively charged head. The hydrocarbon tail is hydrophobic (water repelling) and the negatively charged head is hydrophilic (water-attracting).

The dirt in the cloth is due to the presence of dust particles in fat or grease which stick to the cloth. When soap or detergent is dissolved in water the molecules gather together as clusters called micelles when the dirty cloth is dipped in soap or detergent solution. The soap and dirt particles come in contact with each other.

The non-polar tails of the soap begin to dissolve in non – polar oil or grease. While the polar head part remains in the water. As more and more soap particles enter the grease each fat or oil particle is surrounded by a number of negatively charged ends. Since the similar charges repel each other the oil or grease droplets break off into small globules of oil. These are still surrounded by the negatively charged polar heads of the soap molecules.

This prevents the small globules from coming together to form bigger particles. The rubbing by hands or mechanical stirring also helps to break the grease particles. In this manner, the grease particles can be completely broken up and it forms an emulsion of grease or oil contained in dirt and the droplets are washed away with water.

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Why does physisorption decrease with the increase of temperature ?

Since the adsorption process is exothermic, the physical adsorption occurs readily at low temperature and decreases with increasing temperature (Le-Chatelier’s principle)..

Action of soap is due to emulsification and micelle formation. Comment .

The cleansing action of soap is due to emulsification and micelle formation.

Soaps are basically sodium and potassium salts of long-chain fatty acids,

$R-COO^{-}Na^{+}.$ The end of the molecule to which the sodium it attached is polar in nature, while the alkyl - end is non-polar.

Thus, a soap molecule contains a hydrophilic (polar) and a hydrophobic (non-polar) part.

When soap added to water containing dirt, the soap molecules surround the dirt particles in such a manner that their hydrophobic parts get attached to the dirt molecule, and the hydrophilic parts point away from the dirt molecules. This is known as micelle formation.

Thus we can say that the polar group dissolves in water while the non-polar group dissolves in the dirt particle.

Now, as these micelles are negatively charged, they do not coalesce and a stable emulsion is formed.

Give four uses of emulsions.

Four uses of emulsions :

1. Cleansing action of soap is based on the formation of emulsions.

2. Digestion of fats in intestine takes place by the process of emulsification.

3. Antiseptics and disinfectants when added to water form emulsions.

4. The process of emulsification is used to make medicines.

What is demulsification ? Name two demulsifiers.

The process of decomposition of an emulsion into its constituent liquids is called demulsification .

Examples of demulsifiers are surfactants , ethylene oxide, etc.

It is found that when Litmus is shaken with animal charcoal adsorption takes place
Explain the term "sorption"

The phenomenon in which adsorption and adsorption occur together is called sorption.

Why are powdered substance more effective adsorbent than their crystalline forms?

Powdered substance are more effective adsorbents than their crystalline forms because when a substance is powdered , its surface area increase and physisorption is directly proportional to the surface area of the adsorbent.

Write two difference in adsorption and absorption.

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Describe the following methods for the formation of colloidal solutions:

Bredig - Arc method

The colloidal solution are metals are obtained by this method, The metal, whose sol is to be prepared, is made as two electrodes in a dispersion medium such as water. The dispersion medium is kept cool by surrounding it with a freezing mixture.

An electric arc is struck between the electrodes. The tremendous heat generated by the arc vaporised the metals which are condensed immediately in the liquid to give the colloidal solution. The colloidal solution of the metals is water repellent so a small quantity of KOH is mixed for their stability.

Which adsorbent is used to remove hardness of water ?

The group e.g

$-COOH , -SO_{3}H, -NH_{2}$ etc present in organic polymers are capable of adsorbing specific ions from solution or water. They used to soften the hard water.

List-A	List-B	List-C
(A) Lyophilics	Froth floatation	a. Charge depends on pH
(B) Lyophobics	Organic substances	b. Charge is independent of pH
(C) Protection	Artificial rain	c. Digestion of food
(D) Smoke	Inorganic substances	d. Spray of Agl
(E) Coagulation	Blue tinge	e. Gelatin
(F) Emulsification	Gold number	f. Tyndall effect

Column-I	Column-II
(a) Persorption	(p) $H_2$ on Ni surface
(b) Sorption	(q) $CH_3OH$ in chabazite
(c) Negative adsorption	(r) $NH_3 \,in\, H_2O$
(d) Occlusion	(s) Dil. NaCl on blood charcoal

Surface Chemistry - Class 12 Engineering Chemistry - Extra Questions

What is adsorption?

Name the two groups into which phenomenon of catalysis can be divided. Given an example of each group with the chemical equation involved.

The catalyst used for hydrogenation of oils is __________.

How is Soap industrially manufactured?

Write briefly about the preparation of colloids by chemical methods.

What is catalysis? Give an example.

Name the adsorbent used to removal of colouring matter from solution.

The conductance of an emulsion increases on adding common salt. What type of emulsion is this?

The emulsifying agent forms an interfacial film between suspended particles and the medium. The principal emulsifying agents for O/WO/W emulsions are?

Explain cleaning action?

Describe the cleansing action of soap?

Name the temperature above which the formation of micelles takes place. What type of semiconductor is obtained when silicon is doped with arsenic ?

During the decomposition of hydrogen peroxide glycerine acts as positive catalyst. If this is true enter 1 and if false enter 0.

Explain the mechanism of cleaning action of soap.

Match the List I with the List II.

_________ (Adsorption/Chemisorption) process is involved in the decolourisation of sugar cane juice.

Match list I with list II.

The reaction having catalyst and reactants phase ≥\geq ____________ is heterogeneous catalysis.1 1223300

The reaction in which reactants and the catalyst have one phase is _________ .heterogeneous catalysishomogeneous catalysissolid state catalysissolution catalysis

The phenomenon when a reaction influences the rate of other reaction is ___.homogenous catalysisheterogeneous catalysisinduced catalysiscompetitive catalysis

When one reaction influences the rate of other reaction, which does not occur under ordinary conditions, then this phenomenon is induced catalysis.

Example: Sodium sulphite solution oxidises in the air but sodium arsenite solution does not oxidise by passing air.But when both solutions are mixed and the air is passed through the solution, then both the substances get oxidised.

The substance that __________ the activity of catalysts is poisoner.increasesdecreasesmaintainsnone

The substance that _________ the activity of catalysts is called promoter.IncreasesDecreasesMaintainsNone of the above

Rivers on meeting with oceans form ____________ .estuariesswampsdeltasnone of the aboveChoose the correct option.

Electrostatic precipitation of carbon from smoke is used to control what type of pollution?AirSoilBoth 1 and 2None of the above

In oil solution of soap, the head is towards the surface of the oil and the tail is pointing away from the oil.If the given statement is true, enter 1, else enter 0.

Draw the diagram showing micelle formation by the following detergent.CH3(CH2)10CH2OS¯O3+NaCH_3(CH_2)_{10}CH_2OS\overline{O}_3\overset {+}{N}a

Explain the mechanism of the cleansing action of soaps?

In aqueous solution of soap, head is towards the surface of water and tail is pointing away from the water.if true, enter 1, else enter 0.

Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents like ethanol also?

Adsorption is a phenomenon of accumulation of higher concentration of one substance on the surface of another.State whether True or False.

Peptization is a process of converting a freshly prepared precipitate into a colloidal form by the addition of a suitable electrolyte.State whether the statement is True or False.

Water which gives good lather readily with soap is known as hard water.If this is true enter 1, if false enter 0.

Adsorption is surface phenomenon and absorption is bulk phenomenonIf this is true enter 1, if false enter 0.

If both absorption and adsorption occur simultaneously it is called sorptionIf this is true enter 1, if false enter 0.

Match various processes in surface chemistry from List 1 with their definition from List 2.

The liquid or solid on the surface of which the molecule of the substance are adsorbed is called adsorbate.If this is true enter 1, if false enter 0.

The substance whose molecules are adsorbed is called adsorbent.If this is true enter 1, if false enter 0.

Explain the cleansing action of soaps.

(i) Differentiate between adsorption and absorption.(ii) Out of MgCl2Mg{Cl}_{2} and AlCl3Al{Cl}_{3}, which one is more effective in causing coagulation of negatively charged sol and why?(iii) Out of sulphur sol and proteins, which one forms multimolecular colloids?

Give one example each of lyophobic sol and lyophillic sol.

Explain the following terms giving one example for each:(i) Micelles(ii) Aerosol

What are the dispersed phase and dispersion medium in milk?

Give one example each of 'oil in water' and 'water in oil' emulsion.

A delta is formed at the meeting point of sea water and river water. Why?

What are emulsions? What are their different types? Give one example of each type.

Define peptization.

What are emulsions? What are their different types? Give one example of each type.

What is meant by 'shape selective catalysis'?

Define the following terms with an example in each case:(i) Macromolecular sol (ii) Peptization (iii) Emuslion

What is the difference between oil/water (O/W) type and water/oil (W/O) type emulsions? Give an example of each type.

What are the characteristics of the following colloids? Give one example of each(i) Multimolecular colloids (ii) Lyophobic sols (iii) Emulsions

Explain the cleansing action of soap.

Give one example (equation) of a homogeneously catalysed reaction and name the catalyst.

(a) What is enzyme catalysis? Write an example.(b) Which type of emulsion is milk? Explain.(c) Explain Electrophoresis with labelled diagram.

a) Explain bragg's spectrometer method.b) Write about the preparation of colloids by chemical methods.

What is peptization? Explain.

Explain the mechanism of cleansing action of soaps.

What is emulsifying agent? Give one example?

What is emulsion? How are emulsions classified? Give example?

What are emulsions? How they are classified? Give one example of each.

What is Emulsion?

Write the chemical method by which Fe(OH)3Fe(OH)_{3} sol is prepared from FeCl3FeCl_{3}.

Draw a graph of potential energy v/s reaction coordinate showing the effect of a catalyst on activation energy.

What is Heterogeneous catalysis? Give an example.

Conversion of precipitate into colloidal solution is known as______.

Catalysts which increase rate of a reaction are called ___________ catalyst.

Peptisation is a method of preparation of sols. Write a general procedure for peptization.

What is peptization?

Who used the word 'catalyst' for the first time?

For the coagulation of 100mL100mL of arsenious sulphide solution, 5mL5mL of 1M1M NaClNaCl is required. What is the coagulating power of NaClNaCl?

Match the terms in List 1 with those of List 2.

Match the phenomena in Column-I with example in Column-II:Column-IColumn-II(a) Persorption (p) H2H_2 on Ni surface(b) Sorption (q) CH3OHCH_3OH in chabazite(c) Negative adsorption (r) NH3inH2ONH_3 \,in\, H_2O (d) Occlusion (s) Dil. NaCl on blood charcoal

Define Semipermeable membrane.

What is a catalyst? give one example.

What is scum and how is it formed?

What are the causes of Peptization?

526.3 mL of 0.5 M HCI is shaken with 0.5 g of activated charcoal and filtered. The concentration of the filtrate is reduced to 0.4M. What is the amount of adsorption (x/M)?

The emulsifying agent forms an interfacial film between suspended particles and the medium. The principal emulsifying agents for $O/W$ emulsions are?

Name the temperature above which the formation of micelles takes place.
What type of semiconductor is obtained when silicon is doped with arsenic ?

The reaction having catalyst and reactants phase $\geq$ ____________ is heterogeneous catalysis.
$1$
$2$
$3$
$0$

The reaction in which reactants and the catalyst have one phase is _________ .
heterogeneous catalysis
homogeneous catalysis
solid state catalysis
solution catalysis

The phenomenon when a reaction influences the rate of other reaction is ___.

homogenous catalysis
heterogeneous catalysis
induced catalysis
competitive catalysis

Example:

Sodium sulphite solution oxidises in the air but sodium arsenite solution does not oxidise by passing air.But when both solutions are mixed and the air is passed through the solution, then both the substances get oxidised.

The substance that __________ the activity of catalysts is poisoner.
increases
decreases
maintains
none

The substance that _________ the activity of catalysts is called promoter.
Increases
Decreases
Maintains
None of the above

Rivers on meeting with oceans form ____________ .
estuaries
swamps
deltas
none of the above

Choose the correct option.

Electrostatic precipitation of carbon from smoke is used to control what type of pollution?
Air
Soil
Both 1 and 2
None of the above

In oil solution of soap, the head is towards the surface of the oil and the tail is pointing away from the oil.
If the given statement is true, enter 1, else enter 0.

Draw the diagram showing micelle formation by the following detergent.
$CH_3(CH_2)_{10}CH_2OS\overline{O}_3\overset {+}{N}a$

In aqueous solution of soap, head is towards the surface of water and tail is pointing away from the water.
if true, enter 1, else enter 0.

Adsorption is a phenomenon of accumulation of higher concentration of one substance on the surface of another.
State whether True or False.

Peptization is a process of converting a freshly prepared precipitate into a colloidal form by the addition of a suitable electrolyte.

State whether the statement is True or False.

Water which gives good lather readily with soap is known as hard water.

If this is true enter 1, if false enter 0.

Adsorption is surface phenomenon and absorption is bulk phenomenon
If this is true enter 1, if false enter 0.

If both absorption and adsorption occur simultaneously it is called sorption
If this is true enter 1, if false enter 0.

The liquid or solid on the surface of which the molecule of the substance are adsorbed is called adsorbate.
If this is true enter 1, if false enter 0.

The substance whose molecules are adsorbed is called adsorbent.
If this is true enter 1, if false enter 0.

(i) Differentiate between adsorption and absorption.
(ii) Out of $Mg{Cl}_{2}$ and $Al{Cl}_{3}$ , which one is more effective in causing coagulation of negatively charged sol and why?
(iii) Out of sulphur sol and proteins, which one forms multimolecular colloids?

Explain the following terms giving one example for each:
(i) Micelles
(ii) Aerosol

Define the following terms with an example in each case:
(i) Macromolecular sol (ii) Peptization (iii) Emuslion

What are the characteristics of the following colloids? Give one example of each
(i) Multimolecular colloids (ii) Lyophobic sols (iii) Emulsions

(a) What is enzyme catalysis? Write an example.
(b) Which type of emulsion is milk? Explain.
(c) Explain Electrophoresis with labelled diagram.

a) Explain bragg's spectrometer method.
b) Write about the preparation of colloids by chemical methods.

Write the chemical method by which $Fe(OH)_{3}$ sol is prepared from $FeCl_{3}$ .

For the coagulation of $100mL$ of arsenious sulphide solution, $5mL$ of $1M$ $NaCl$ is required. What is the coagulating power of $NaCl$ ?

Match the phenomena in Column-I with example in Column-II:
Column-I
Column-II
(a) Persorption (p) $H_2$ on Ni surface
(b) Sorption (q) $CH_3OH$ in chabazite
(c) Negative adsorption (r) $NH_3 \,in\, H_2O$
(d) Occlusion (s) Dil. NaCl on blood charcoal

In the reaction below the substance acting as a catalyst : -
${ 2KCIO }_{ 3 }\rightarrow 2KCI+{ 3O }_{ 2 }$

Classify into alkanes, alkenes and alkynes :
Ethane, ethene, methane, ethyne, propene, propyne

Name the structure shown in the figure. Also label $1$ and $2$

(a) Explain the process of preparation of soap in laboratory.
(b) Why is common salt (sodium chloride) added during the preparation of soap?
(c) Why is soap not suitable for washing clothes when the water is hard?

Define the following term:
Emulsifying agents

(a) What is a soap? Name one soap.
(b) Describe the structure of a soap molecule with the help of a diagram.
(c) Explain the cleansing action of soap. Draw diagrams to illustrate your answer.

(a) How is ethanoic acid obtained from ethanol? Write down the chemical equation of the reaction involved.
(b) How would you distinguish between ethanol and ethanoic acid by chemical test?
(c) Explain the formation of scum when hard water is treated with soap.

Answer the following question.
Out of silica gel and anhydrous $CaCl_{2}$ , which will adsorb the water vapours?

How are the following collodial solutions prepared?
i. Sulphur in water
ii. Gold in water.

Answer the following questions.
What happens when a freshly precipitated $Fe(OH)_{3}$ is shaken with water containing a small quantity of $FeCl_{3}$ ?

Explain what is observed when.
Silver nitrate solution is added to potassium iodide solution.

Explain the following observation:
Sun looks red at the time of setting.

Complete the missing components/variables given as x in the following reaction:

$C a C O_{3} \stackrel{x}{\longrightarrow} C a O(s)+C O_{2}(g)$

Give the reasons:

Alum purifies drinking water.

The volume of nitrogen gas $V_m$ (measured at S.T.P.) required to cover a sample of silica gel with a mono- molecular layer is $129 cm^3 g^{-1}$ of gel. Calculate the surface area per gram of the gel if each nitrogen molecule occupies $16.2 \times 10^{-20} m^2$ .

$SnO_2$ forms a positively charged colloidal sol in acidic medium and a negatively charged sol in the basic medium. Why? Explain.

Explain the following giving a suitable example for each.
(i) Aerosol (ii) Emulsion (iii) Micelle

Write one difference in each of the following:
(a) Multimolecular colloid and Associated colloid
(b) Coagulation and Peptization
(c) Homogeneous catalysis and Heterogeneous catalysis

a) Which types of an emulsion is 'vanishing cream'. Write its appropriate name.
b) Draw neat and labelled diagram of above emulsion.