Explore topic-wise InterviewSolutions in .

(a) Dialysis- it is a process of removing a dissolved substance from a colloidal solution by membrane. 

(b) Electro dialysis- when dialysis is carried out with an electric field applied around the membrane. 

(c) Ultra filtration- Use of special filters which are permeable to all ionic substances except colloidal particles. 

Types of Colloids:

(1) On the basis of nature of interaction between dispersed phase and dispersion medium. 

(a) Lyophobic colloid- solvent , hating colloid, these colloids can not be prepared by simply mixing of dispersed phase into dispersion medium. e.g. metallic sols. 

(b) Lyophillic colloid- solvent loving these colloids can be prepared by simply mixing of dispersion phase into dispersion medium. e.g. Starch sol. 

(2) On the basis of types of particles of the dispersed phase 

(a) Multimolecular colloid- on dissolution, a large number of atoms or smaller molecules of a substance aggregate together to form species having size in colloidal range. The species thus formed are called Multimolecular colloids. e.g. Sulphur sol. 

(b) Macromolecular colloids -macromolecules are suitable solvent from solution in which size of the particles are in range of colloidal range. e.g. starch sol. 

(c) Associated colloids (micelles)- some substances in law concentration behaves as normal strong electrolyte but at higher concentration exhibit colloidal behavior due to formation of aggregates. The aggregated particles are called micelles and also known as associated colloids. 

(3) Kraft temperature- Temp. above which formation of micelles takes places. 

(4) Critical micelle concentration (cmc) - concentration above which micelle formation takes place is known as cmc. 

A colloid is a heterogeneous system in which one substance is dispersed(dispersed phase)in another substance called dispersion medium and size of dispersed phase is from 1 nm -1000 nm. 

Characteristic of enzyme catalysis – 

a. Enzymes are specific to substrate. 

b. Enzymes are highly active under optimum temperature. 

c. Enzymes are specific to pH.e.g. Pepsin act in acidic medium 

d. Enzymes are inhabited by the presence of certain substance. 

Mechanism of enzyme catalysis – 

1. Binding of enzyme to substrate to form an activated complex. 

E + S � → ES* 

2. Decomposition of activated complex to form product. 

ES → E + P 

Enzymes are protein molecules of high molecular mass which catalyse the biochemical reaction. 

e.g. Inversion of cane sugar by invertase enzyme. 

The substances that enhance the activity of a catalyst are called promoters.

(i) Same reactants may give different product by using different catalysts.

(ii) Catalyst does not change ΔH of reaction.

When gaseous molecules come in contact with the surface of a solid catalyst, a weak chemical combination takes place between the surface of the catalyst and the gaseous molecules, which increases the concentration of reactants on the surface. Different moelcules adsorbed side by side have better chance to react and form new molecules. This enhances the rate of reaction. Also, adsorption is an exothermic process. The heat released in the process of adsorption is utilised in enhancing the reaction rate.

The optimum temperature range for enzymatic activity is 298- 310 K. On either side of this temperature range, enzymatic activity gets affected. Thus, during fever, when temperature rises above 310 K, the activity of enzymes may be affected.

Physisorption is exothermic in nature. Therefore, in accordance with Le-Chateliere’s principle, it decreases with an increase in temperature. This means that physisorption occurs more readily at a lower temperature.

Ester hydrolysis can be represented as: Ester + water → Acid + Alcohol. The acid produced in the reaction acts as a catalyst and makes the reaction faster, substances that act as catalysts in the same reaction in which they are obtained as products are known as anticatalysts.

The molecules of dispersion medium due to their kinetic motion strike against the colloidal particles (dispersed phase) from all sides with different forces causing them to move.

Suspension > colloidal > true solution. 

(v) Assertion is incorrect but reason is correct.

The process of dialysis used for the purification of colloids can be accelerated by applying an electric field. The oppositely charged ions of the electrolyte present in the colloids migrate towards the respective electrodes easily.

Haber’s process for the manufacture of ammonia,iron is used as catalyst. Contact process for the manufacture of sulphuric acid, V₂O₅ is used as catalyst.

(ii) associated colloid

Correct answer is (i) (b), (c)

When an ester is treated with mineral acid, gives an acid and alcohol. The organic acid undergoes dissociation to give hydrogen ions. These hydrogen ions act as catalyst and hence and the hydrolysis becomes faster.

(a) Zeolites are aluminosilicates having three dimensional structure. Zeolites are highly porous have cavities of different sizes. The catalytic behaviour of zeolite catalysts depends upon the size of the cavities in them, which usually varies from 260-740 pm. The reaction molecules of a particular shape and size can only enter and get absorbed. Thus Zeolites are called shape selective catalysts. 

(b) Colloidal particles move towards one or other electrode. Phenomenon is called electrophoresis.

It is defined as the scattering of light by the colloidal particles present in a colloidal solution.

(d) all of these

(a)  4 1 2 3

(a)  3 1 4 2

Chemisorption. Because of the formation of chemical bond.

(a) Both magnitude and sign of the charge on the ion.

Physisorption

Important characteristics of physisorption:

1. It is reversible 

2. It has low heat of adsorption 

3. It has weak van der Waals forces of attraction with adsorbent. 

4. It increases with increase in pressure. 

5. It forms multimolecular layer.

(d) (iv) (iii) (ii) (i)

(ii), (iii)

(ii) Micelle formation by soap in aqueous solution occurs above a particular concentration.

(iii) On dilution of soap solution micelles may revert to individual ions.

(iv) Absorption of ionic species from solution.

SO₂ is liquefiable gas

N₂ is a permanent gas.

(b) A is correct and R is the correct explanation of A

NH₃ gases is not a permanent gas.

(b) CH₃ – (CH₂)₁₅ – NH₂ 

(b) III > II > I > IV

Higher the critical temperature of the gas. Greater is the ease of liquefaction. i.e. greater Vander walls forces of attraction and hence large adsorption will occur. 

Adsorption is a surface phenomena while absorption is bulk phenomena.

1. The nature of adsorbate can influence the adsorption. Gases like NH₃ CO₂ are easily liquefiable as have greater van der Waals forces of attraction and hence readily adsorbed due to high critical temperature.

2. But permanent gases like H₂ , N₂ can not be easily liquefied and having low critical temperature and adsorbed slowly.

Freundlinch adsorption isotherm

\(\frac{x}{m}\) = kp^1/n 

where x is the amount of adsorbate or adsorbed on ‘m’ gm of adsorbent at a pressure of p. k and n arc constants.

(a) When light rays travel through colloidal solution:

When light rays are allowed to pass through a true solution then this light does not seen in solution till the eyes have not close in the path of direction of light. But when light beam is passed through colloidal solution then this light is seen in the form of bright line. The phenomenon is called Tyndall effect.

(b) Electric current is passed through colloidal solution:

Electric current is passed through colloidal solution then the movement of colloidal particles observe towards oppositely charged electrodes in presence of electric field. This phenomenon is called electrophoresis.

The answer is (a) AlCl₃

Characteristics of enzyme catalysis:

1. Highly effective:
Enzyme catalysts increase the rate of reactions by 10⁸ to 10²⁰ times as compared to the uncatalysed reaction.

2. Temperature and pH:
The enzyme catalysis is active at average temperature (37°C or 25-37°C) and certain pH (pH = 7)

3. Small amount:
Very small amount of enzyme increases the rates of reactions by 10% to 106 times.

4. Specificity:
Enzymes are very specific in nature. One enzyme can act as catalyst in reaction.