CBSE Class 12 Chemistry Surface Chemistry Worksheet Set 04

Question. Which one of the following is not applicable to the phenomenon of adsorption? 
(A) ΔH > 0
(B) ΔG < 0
(C) ΔS < 0
(D) ΔH < 0
Answer : A

Question. Which of the following is an example of absorption? 
(A) Water on Silica gel
(B) Water on Calcium Chloride
(C) Hydrogen on highly divided Nickel
(D) Oxygen on Metal surface
Answer : B

Question. Which is the example of emulsions? 
(A) Smoke
(B) Starch
(C) Gold Sol
(D) Hair Cream
Answer : D

Question. Which of the following is the most effective in coagulating positively charged methylene blue sol?
(A) Na₃PO₄
(B) K₄ [Fe(CN)₆]
(C) Na₂SO₄
(D) Al₂(SO₄)₃
Answer : B

Question. On the basis of data given below predict which of the following gases shows least adsorption on a definite amount of charcoal?
Gas CO₂ SO₂ CH₄ H₂
Critical temp/K 304 630 190 33
(A) CO₂
(B) SO₂
(C) CH₄
(D) H₂
Answer : D

Question. Extent of adsorption of adsorbate from solution phase increases with: 
(A) increase in amount of adsorbate in solution.
(B) decrease in surface area of adsorbent.
(C) increase in temperature of solution.
(D) decrease in amount of adsorbate in solution.
Answer : A

Question. In physisorption, adsorbent does not show specificity for any particular gas because :
(A) involved Van der Waals forces are universal.
(B) gases involved behave like ideal gases.
(C) enthalpy of adsorption is low.
(D) it is a reversible process.
Answer : A

Question. Which of the following is not a favourable condition for Physical adsorption? 
(A) High pressure
(B) Negative dH
(C) Higher critical temperature of adsorbate
(D) High temperature
Answer : D

Question. Which of the following interface cannot be obtained? 
(A) Liquid-liquid
(B) Solid-liquid
(C) Liquid-gas
(D) Gas-gas
Answer : D

Question. Method by which lyophobic sol can be protected :
(A) by addition of oppositely charged sol.
(B) by addition of an electrolyte.
(C) by addition of lyophilic sol.
(D) by boiling.
Answer : C

Question. Which of the following is most effective in coagulating negatively charged hydrated Ferric Oxide sol?
(A) NaNO₃
(B) MgSO₄
(C) AlCl₃
(D) KCl
Answer : C

Question. 10. Which of the following is most effective in coagulating positively charged hydrated Ferric Oxide sol?
(A) NaNO₃
(B) Na₂SO₄
(C) (NH₄)₃PO₄
(D) LiAlH₄
Answer : C

Question. Freshly prepared precipitate sometimes gets converted to colloidal solution by: 
(A) coagulation.
(B) electrolysis.
(C) diffusion.
(D) peptisation.
Answer : D

Question. A colloidal system having a solid substance as a dispersed phase and a liquid as a dispersion medium is classified as . 
(A) Solid sol
(B) Gel
(C) Emulsion
(D) Sol
Answer : D

Question. The values of colligative properties of colloidal solution are of small order in comparison to those shown by true solutions of same concentration because of colloidal particles _____________. 
(A) exhibit enormous surface area.
(B) remain suspended in the dispersion medium.
(C) form lyophilic colloids.
(D) are comparatively less in number.
Answer : D

Question. Which of the following will show Tyndall effect? 
(A) Aqueous solution of soap below critical micelle concentration.
(B) Aqueous solution of soap above critical micelle concentration.
(C) Aqueous solution of sodium chloride.
(D) Aqueous solution of sugar.
Answer : B

Assertion and Reason Based MCQs

Directions: In the following questions, a statement of Assertion (A) is followed by a statement of Reason (R).
Mark the correct choice as:
(A) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(B) Both (A) and (R) are true, but (R) is not the correct explanation of (A).
(C) (A) is true, but (R) is false.
(D) (A) is false, but (R) is true.

Question. Assertion (A): Extent of adsorption of adsorbate from solution phase increases with increase in amount of adsorbate in solution.
Reason (R): Freundlich’s equation describes the behaviour of adsorption from a solution.
Answer : A

Question. Assertion (A): Colloidal solutions show colligative properties.
Reason (R): Colloidal particles are large in size.
Answer : B

Question. Assertion (A): Coagulation power of Al³⁺ is more than Na⁺ in the coagulation of negative sol.
Reason (R): Greater the valency of the flocculating ion added, greater is its power to cause precipitation (Hardy-Schulze rule).
Answer : A

Question. Assertion (A): An ordinary filter paper impregnated with colloidal solution stops the flow of colloidal particles.
Reason (R): Pore size of the filter paper becomes more than the size of colloidal particle. 
Answer : C

Question. Assertion (A): Activated adsorption is also known as chemical adsorption or chemisorption.
Reason (R): Adsorption involves formation of chemical bonds between adsorbent and reactants.
Answer : A

Question. Assertion (A): At the equilibrium position in the process of adsorption ∆H = T∆S.
Reason (R): Adsorption is accompanied by decrease in surface energy. R
Answer : B

Question. Assertion (A): Extent of physisorption of a gas increases with decrease in temperature.
Reason (R): Extent of physiorption increases due to decrease in strength of Van der Waals forces. 
Answer : C

Question. Assertion (A): Colloidal solutions do not show brownian motion.
Reason (R): Brownian motion is responsible for stability of Sols. 
Answer : D

Question. Assertion (A): Detergents with low CMC are more economical to use.
Reason (R): Cleansing action of detergents involves the formation of micelles. These are formed when the concentration of detergents becomes equal to CMC. 
Answer : A

Question. Assertion (A): Colloidal solution are stable sols.
Reason (R): Brownian movement has a stirring effect, which does not allow the particles to settle down. 
Answer : A

Case-based MCQs

I. Read the passage given below and answer the following questions:
The amount of moisture that leather adsorbs or loses is determined by the temperature, relative humidity, degree of porosity and the size of the pores. Moisture has great practical significance because its amount affects the durability of leather and the comfort of the wearer in articles such as shoes, gloves and other garments. High moisture content accelerates deterioration and promotes mildew action. On the other hand, a minimum amount of moisture is required to keep leather properly lubricated and thus, prevent cracking.
The study indicates that adsorption of moisture by leather is a multi-molecular process and is accompanied by low enthalpies of adsorption. Further at 75 percent relative humidity, the adsorption is a function of surface area alone.
Untanned hide and Chrome tanned leathers have the largest surface areas. The leathers tanned with vegetable tanning materials have smaller surface areas since they are composed of less hide substance and the capillaries are reduced to smaller diameters in some cases probably completely filled by tanning materials. This process of tanning occurs due to mutual coagulation of positively charged hide with negatively charged tanning material.
The result of the study indicated that untanned hide and Chrome tanned leather adsorb most of the water vapour. 

In these questions a statement of Assertion followed by a statement of Reason is given. Choose the correct answer out of the following choices.
(A) Assertion and reason both are correct statements and reason is correct explanation for assertion.
(B) Assertion and reason both are correct statements but reason is not correct explanation for assertion.
(C) Assertion is correct statement but reason is wrong statement.
(D) Assertion is wrong statement but reason is correct statement.

Question. Assertion (A): Vegetable tanned leather cannot adsorb a large amount of moisture.
Reason (R): Porous materials have higher surface area. 
Answer : B

Question. Assertion (A): Leathers tanned with vegetable tanning materials have smaller surface areas.
Reason (R): The capillaries present in leather are reduced to smaller diameters. 
Answer : A

Question. Assertion (A): Leather absorbs different amount of moisture.
Reason (R): Some moisture is necessary to prevent cracking of leather.
Answer : B

Question. Assertion (A): Animal hide soaked in tannin results in hardening of leather.
Reason (R): Tanning occurs due to mutual coagulation. 
Answer : A

Question. Assertion (A): Adsorption of moisture by leather is physisorption.
Reason (R): It is a multimolecular process and is accompanied by low enthalpies of adsorption. 
Answer : A

II. Read the passage given below and answer the following questions: U
Some colloids are stable by their nature, i.e., gels, alloys, and solid foams. Gelatin and jellies are the two common examples of a gel. The solid and liquid phases in a gel are interpersed with both phases being continuous. In most systems, the major factor influencing the stability is the charge on the colloidal particles. If a particular ion is preferentially adsorbed on the surface of the particles, the
particles in suspension will repel each other, thereby preventing the formation of aggregates that are larger than colloidal dimensions. The ion
can be either positive or negative depending on the particular colloidal system, i.e., air bubbles accumulate negative ions. Sulphur particles have a net negative charge in a sulphur sol, and the particles in a metal hydroxide sol are positively charged. Accumulation of charge on a surface is not
as usual phenomenon of dust attracted to furniture surfaces by electrostatic forces. When salts are added to lyophobic colloidal systems the colloidal particles begin to form larger aggregates and a sediment forms as they settle. This phenomenon is called flocculation, and the suspension can be referred to as flocculated, or colloidally unstable. If  the salt is removed, the suspension can usually be restored to its original state; this process is called Deflocculation or Peptization. The original and restored colloidal systems are called deflocculated, peptized, or stable sols. Addition of small amount of salt affects the stability of colloidal system because of attractive and repulsive forces that exist between colloidal particles. Van der Waals forces are responsible for the attractions, while the repulsive forces are due to the surface charge on the particles. In a stable colloid, the repulsive forces are of greater magnitude than the attractive forces. The magnitude of the electrical repulsion is diminished by addition of ionized salt, which allows the dispersed particles to aggregate and flocculate. River deltas provide an example of this behaviour.

Question. Gelatin is a ________________ colloidal system.
(A) Solid in solid
(B) Solid in gas
(C) Liquid in solid
(D) Liquid in gas
Answer : C

Question. Settling down of colloidal particles to form a suspension is called:
(A) Flocculation
(B) Precipitation
(C) Aggregation
(D) All of the above
Answer : D

Question. When Van der Waals forces are greater than forces due to the surface charge on the particles:
(A) Flocculation occurs.
(B) The colloid is stable.
(C) Peptization takes place.
(D) Deflocculation occurs.
Answer : A

Question. Colloidal solutions are stable due to:
(A) presence of charges on the colloidal particles.
(B) formation of aggregates by colloidal particles.
(C) preferential adsorption on the surface.
(D) preferential absorption on the surface.
Answer : A

Question. The particles in suspension will repel each other, thereby preventing the formation of aggregates that are larger than colloidal dimensions. This statement explains:
(A) formation of delta.
(B) river water as a colloidal solution of clay particles.
(C) effect of salt on lyophobic colloid.
(D) phenomenon of flocculation.
Answer : A, B

Please click on below link to download CBSE Class 12 Chemistry Surface Chemistry Worksheet Set A