Chemistry

Surface Chemistry

Question:

Method of formation of solution is given in Column I. Match it with the type of solution given in Column II.
ncert-exemplar-problems-class-12-chemistry-surface-chemistry-17

Answer:

(i - »b), (ii —> c), (iii — » d), (iv —> a)
(i) When sulphur vapour passed through cold water, it leads to formation of molecular colloids.
(ii) When soap is mixed with water above critical micelle concentration, it leads to formation of associated colloids.
(iii) White part of egg whipped with water is an example of macro-molecular colloids in which high molecular mass proteneous molecule acts as a colloidal particle.
(iv) Soap mixed with water below critical micelle concentration is known as normal electrolyte solution.

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Surface Chemistry

Q 1.

Why is the ester-hydrolysis slow in the beginning and becomes faster after sometime?

Q 2.

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

Q 3.

Why is chemisorption referred to as activated adsorption?

Q 4.

What type of solutions are formed on dissolving different concentrations of soap in water?

Q 5.

Why do physisorption and chemisorption behave differently with rise in temperature?

Q 6.

In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the following choices:
(a) Both Assertion and Reason are correct and the Reason is the correct explanation for Assertion.
(b) Both Assertion and Reason arc correct but Reason is not the correct explanation for Assertion.
(c) Assertion is correct but Reason is incorrect.
(d) Both Assertion and Reason are incorrect.
(e) Assertion is incorrect but Reason is correct

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

Q 7.

What role does adsorption play in heterogeneous catalysis?

Q 8.

Explain what is observed
(i) when a beam of light is passed through a colloidal sol.
(ii) an electrolyte, NaCI is added to hydrated ferric oxide sol.
(iii) electric current is passed through a colloidal sol.

Q 9.

A colloid is formed by adding FeCl3  in excess of hot water. What will happen if excess sodium chloride is added to this colloid?

Q 10.

What causes Brownian motion in colloidal dispersion?

Q 11.

Why does physisorption decrease with the increase of temperature?

Q 12.

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

Q 13.

Gelatin which is a peptide added in ice-creams. What can be its role?

Q 14.

Give an example where physisorption changes to chemisorption with rise in temperature. Explain the reason for change.

Q 15.

What are the applications of adsorption in chemical analysis?

Q 16.

What are lyophilic and lyophobic sols? Give one example of each type. Why are hydrophobic sols easily coagulated?

Q 17.

Which of the following electrolytes will have maximum coagulating value
ncert-exemplar-problems-class-12-chemistry-surface-chemistry-7

Q 18.

Why is it essential to wash the precipitate with water before estimating it quantitatively?

Q 19.

What is an adsorption isotherm? Describe Freundlich adsorption isotherm.

Q 20.

Give four examples of heterogeneous catalysis.

Q 21.

Why does the white precipitate of silver halide become coloured in the presence of dye eosin.

Q 22.

Why are powdered substances more effective . adsorbents than their crystalline forms?

Q 23.

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

Q 24.

What is collodion?

Q 25.

What happens when dialysis is prolonged?

Q 26.

What is the role of adsorption in froth floatation process used especially for concentration of sulphide ores?

Q 27.

Write any two characteristics of Chemisorption.

Q 28.

What is the role of desorption in the process of catalysis.

Q 29.

Which of the following phenomenon occurs when a chalk stick is dipped in ink?
(a) Adsorption of coloured substance
(b) Adsorption of solvent
(c) Absorption and adsorption both of solvent
(d) Absorption of solvent.

Q 30.

Which of the following phenomenon occurs when a chalk stick is dipped in ink?
(a) Adsorption of coloured substance
(b) Adsorption of solvent
(c) Absorption and adsorption both of solvent
(d) Absorption of solvent.

Q 31.

Why is chemisorption referred to as activated adsorption?

Q 32.

Why is Fe(OH)3colloid positively charged, when prepared by adding FeCl3 to hot water?

Q 33.

What is the role of activated charcoal in gas mask used in coal mines?

Q 34.

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.

Q 35.

What is the role of adsorption in heterogeneous catalysis?

Q 36.

What are enzymes? Write in brief the mechanism of enzyme catalysis.

Q 37.

In a reaction, catalyst changes  
(a) physically (b) qualitatively
(c) chemically (d) quantitatively

Q 38.

Why is it important to have clean surface in surface studies?

Q 39.

What happens when gelatin is mixed with gold sol?

Q 40.

How does a delta form at the meeting place of sea and river water?

Q 41.

Match the types of colloidal systems given in Column I with the name given in Column II.
ncert-exemplar-problems-class-12-chemistry-surface-chemistry-20

Q 42.

What modification can you suggest in the Hardy Schulze, law?

Q 43.

H2 gas is adsorbed on activated charcoal to a very little extent in comparison
to easily liquefiable gases due to
(a) very strong van der Waals interaction
(b) very weak van der Waals forces
(c) very low critical temperature
(d) very high critical temperature.

Q 44.

Which of the following statements are correct?
(a) Mixing two oppositely charged sols neutralizes their charges and stabilizes the colloid.
(b) Presence of equal and similar charges on colloidal particles provides stability to the colloids.
(c) Any amount of dispersed liquid can be added to emulsion without destabilizing it.
(d) Brownian movement stabilizes sols.

Q 45.

What do you understand by shape selective catalysis? Why are zeolites good shape selective catalysts?

Q 46.

What do you understand by activation of adsorbent? How is it achieved?

Q 47.

How do emulsifires stabilise emulsion? Name two emulsifiers.

Q 48.

What do you mean by activity and selectivity of catalysts?

Q 49.

Which of the following phenomenon is applicable to the process shown in the figure?
ncert-exemplar-problems-class-12-chemistry-surface-chemistry-13

Q 50.

Which phenomenon occurs when an electric field is applied to a-colloidal solution and electrophoresis is prevented?
(a) Reverse osmosis takes place.
(b) Electroosmosis takes place.
(c) Dispersion medium begins to move.
(d) Dispersion medium becomes stationary.