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Class Twelve Chemistry

Surface Chemistry-NCERT Exemplar Problems & Solution

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MCQs-Type-I

Question: 1. Which of the following process does not occur at the interface of phases?

(i) crystallisation

(ii) heterogenous catalysis

(iii) homogeneous catalysis

(iv) corrosion

Answer: (iii) homogeneous catalysis

Question: 2. At the equilibrium position in the process of adsorption ___________.

(i) `DeltaH\ >\ 0`

(ii) `DeltaH = TDeltaS`

(iii) `DeltaH\ >\ TDeltaS`

(iv) `DeltaH\ <\ TDeltaS`

Answer: (ii) `DeltaH = TDeltaS`

Question: 3. Which of the following interface cannot be obtained?

(i) liquid-liquid

(ii) solid-liquid

(iii) liquid-gas

(iv) gas-gas

Answer: (iv) gas-gas

Question: 4. The term 'sorption' stands for ____________.

(i) absorption

(ii) adsorption

(iii) both absorption and adsorption

(iv) desorption

Answer: (iii) both absorption and adsorption

Question: 5. Extent of physisorption of a gas increases with ___________.

(i) increase in temperature.

(ii) decrease in temperature.

(iii) decrease in surface area of adsorbent.

(iv) decrease in strength of van der Waals forces.

Answer: (ii) decrease in temperature.

Question: 6. Extent of adsorption of adsorbate from solution phase increases with ________.

(i) increase in amount of adsorbate in solution.

(ii) decrease in surface area of adsorbent.

(iii) increase in temperature of solution.

(iv) decrease in amount of adsorbate in solution.

Answer: (i) increase in amount of adsorbate in solution.

Question: 7. Which one of the following is not applicable to the phenomenon of adsorption?

(i) `DeltaH\ >\ 0`

(ii) `DeltaG\ <\ 0`

(iii) `DeltaS\ <\ 0`

(iv) `DeltaH\ <\ 0`

Answer: (i) `DeltaH\ >\ 0`

Question: 8. Which of the following is not a favourable condition for physical adsorption?

(i) high pressure

(ii) negative `DeltaH`

(iii) higher critical temperature of adsorbate

(iv) high temperature

Answer: (iv) high temperature

Question: 9. Physical adsorption of a gaseous species may change to chemical adsorption with ______________.

(i) decrease in temperature

(ii) increase in temperature

(iii) increase in surface area of adsorbent

(iv) decrease in surface area of adsorbent

Answer: (ii) increase in temperature

Question: 10. In physisorption adsorbent does not show specificity for any particular gas because ______________.

(i) involved van der Waals forces are universal.

(ii) gases involved behave like ideal gases.

(iii) enthalpy of adsorption is low.

(iv) it is a reversible process.

Answer: (i) involved van der Waals forces are universal.

Question: 11. Which of the following is an example of absorption?

(i) Water on silica gel

(ii) Water on calcium chloride

(iii) Hydrogen on finely divided nickel

(iv) Oxygen on metal surface

Answer: (ii) Water on calcium chloride

Question: 12. On the basis of data given below predict which of the following gases shows least adsorption on a definite amount of charcoal?

Gas `CO_2` `SO_2` `CH_4` `H_2`
Critical temp./K 304 630 190 33

(i) `CO_2`

(ii) `SO_2`

(iii) `CH_4`

(iv) `H_2`

Answer: (iv) `H_2`

Question: 13. In which of the following reactions heterogenous catalysis is involved?

(a) `2SO_2(g)+O_2(g) stackrel"NO(g)"->2SO_3(g)`

(b) `2SO_2(g) stackrel"Pt(s)"->2SO_3(g)`

(c)`N_2(g)+3H_2(g) stackrel"Fe(s)"->2NH_3(g)`

(d) `CH_3COOCH_3(l)+H_2O stackrel"HCl(l)"->CH_3COOH(aq)+CH_3OH(aq)`

(i) (b), (c)

(ii) (b), (c), (d)

(iii) (a), (b), (c)

(iv) (d)

Answer: (i) (b), (c)

Question: 14. At high concentration of soap in water, soap behaves as ____________.

(i) molecular colloid

(ii) associated colloid

(iii) macromolecular colloid

(iv) lyophilic colloid

Answer: (ii) associated colloid

Question: 15. Which of the following will show Tyndall effect?

(i) Aqueous solution of soap below critical micelle concentration.

(ii) Aqueous solution of soap above critical micelle concentration.

(iii) Aqueous solution of sodium chloride.

(iv) Aqueous solution of sugar.

Answer: (ii) Aqueous solution of soap above critical micelle concentration.

Question: 16. Method by which lyophobic sol can be protected.

(i) By addition of oppositely charged sol.

(ii) By addition of an electrolyte.

(iii) By addition of lyophilic sol.

(iv) By boiling.

Answer: (iii) By addition of lyophilic sol.

Question: 17. Freshly prepared precipitate sometimes gets converted to colloidal solution by ___________.

(i) coagulation

(ii) electrolysis

(iii) diffusion

(iv) peptisation

Answer: (iv) peptisation

Question: 18. Which of the following electrolytes will have maximum coagulating value for `AgI//Ag^+` sol?

(i) `Na_2S`

(ii) `Na_3PO_4`

(iii) `Na_2SO_4`

(iv) `NaCl`

Answer: (ii) `Na_3PO_4`

Question: 19. A colloidal system having a solid substance as a dispersed phase and a liquid as a dispersion medium is classified as ____________.

(i) solid sol

(ii) gel

(iii) emulsion

(iv) sol

Answer: (iv) sol

Question: 20. 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 __________________.

(i) exhibit enormous surface area.

(ii) remain suspended in the dispersion medium.

(iii) form lyophilic colloids.

(iv) are comparatively less in number.

Answer: (iv) are comparatively less in number.

Question: 21. Arrange the following diagrams in correct sequence of steps involved in the mechanism of catalysis, in accordance with modern adsorption theory.

(a) class 12 exemplar problems and solution surface chemistry1

(b) class 12 exemplar problems and solution surface chemistry2

(c) class 12 exemplar problems and solution surface chemistry3

(d) class 12 exemplar problems and solution surface chemistry4

(e) class 12 exemplar problems and solution surface chemistry5

(i) a→b→c→d→e

(ii) a→c→b→d→e

(iii) a→c→b→e→d

(iv) a→b→c→e→d

Answer: (ii) a→c→b→d→e

Question: 22. Which of the following process is responsible for the formation of delta at a place where rivers meet the sea?

(i) Emulsification

(ii) Colloid formation

(iii) Coagulation

(iv) Peptisation

Answer: (iii) Coagulation

Question: 23. Which of the following curves is in accordance with Freundlich adsorption isotherm?

(i) class 12 exemplar problems and solution surface chemistry6

(ii) class 12 exemplar problems and solution surface chemistry7

(iii) class 12 exemplar problems and solution surface chemistry8

(iv) class 12 exemplar problems and solution surface chemistry9

Answer: (iii) class 12 exemplar problems and solution surface chemistry8

Question: 24. Which of the following process is not responsible for the presence of electric charge on the sol particles?

(i) Electron capture by sol particles.

(ii) Adsorption of ionic species from solution.

(iii) Formation of Helmholtz electrical double layer.

(iv) Absorption of ionic species from solution.

Answer: (iv) Absorption of ionic species from solution.

Question: 25. Which of the following phenomenon is applicable to the process shown in the Figure?

class 12 exemplar problems and solution surface chemistry10

(i) Absorption

(ii) Adsorption

(iii) Coagulation

(iv) Emulsification

Answer: (ii) Adsorption

Multiple Choice Questions (Type-II)

Note : In the following questions two or more options may be correct.

Question: 26. Which of the following options are correct?

(i) Micelle formation by soap in aqueous solution is possible at all temperatures.

(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) Soap solution behaves as a normal strong electrolyte at all concentrations.

Answer:

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

And

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

Question: 27. Which of the following statements are correct about solid catalyst?

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

(ii) Catalyst does not change `DeltaH` of reaction.

(iii) Catalyst is required in large quantities to catalyse reactions.

(iv) Catalytic activity of a solid catalyst does not depend upon the strength of chemisorption.

Answer:

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

And

(ii) Catalyst does not change `DeltaH` of reaction.

Question: 28. Freundlich adsorption isotherm is given by the expression `x/m = k\ p^(1/n)` which of the following conclusions can be drawn from this expression.

(i) When `1/n=0`, the adsorption is independent of pressure.

(ii) When `1/n=0`, the adsorption is directly proportional to pressure.

(iii) When `n = 0`, `x/m` vs `p` graph is a line parallel to x-axis.

(iv) When n = 0, plot of `x/m` vs `p` is a curve.

Answer:

(i) When `1/n=0`, the adsorption is independent of pressure.

And

(iii) When `n = 0`, `x/m` vs `p` graph is a line parallel to x-axis.

Question: 29. H2 gas is adsorbed on activated charcoal to a very little extent in comparison to easily liquefiable gases due to ____________.

(i) very strong van der Waal's interaction.

(ii) very weak van der Waals forces.

(iii) very low critical temperature.

(iv) very high critical temperature.

Answer:

(ii) very weak van der Waals forces.

And

(iii) very low critical temperature.

Question: 30. Which of the following statements are correct?

(i) Mixing two oppositely charged sols neutralises their charges and stabilizes the colloid.

(ii) Presence of equal and similar charges on colloidal particles provides stability to the colloids.

(iii) Any amount of dispersed liquid can be added to emulsion without destabilising it.

(iv) Brownian movement stabilises sols.

Answer:

(ii) Presence of equal and similar charges on colloidal particles provides stability to the colloids.

And

(iv) Brownian movement stabilises sols.

Question: 31. An emulsion cannot be broken by __________ and ___________.

(i) heating

(ii) adding more amount of dispersion medium

(iii) freezing

(iv) adding emulsifying agent

Answer:

(ii) adding more amount of dispersion medium

And

(iv) adding emulsifying agent

Question: 32. Which of the following substances will precipitate the negatively charged emulsions?

(i) KCl

(ii) glucose

(iii) urea

(iv) NaCl

Answer:

(i) KCl

And

(iv) NaCl

Question: 33. Which of the following colloids cannot be coagulated easily?

(i) Lyophobic colloids.

(ii) Irreversible colloids.

(iii) Reversible colloids.

(iv) Lyophilic colloids.

Answer:

(iii) Reversible colloids.

And

(iv) Lyophilic colloids.

Question: 34. What happens when a lyophilic sol is added to a lyophobic sol?

(i) Lyophobic sol is protected.

(ii) Lyophilic sol is protected.

(iii) Film of lyophilic sol is formed over lyophobic sol.

(iv) Film of lyophobic sol is formed over lyophilic sol.

Answer:

(i) Lyophobic sol is protected.

And

(iii) Film of lyophilic sol is formed over lyophobic sol.

Question: 35. Which phenomenon occurs when an electric field is applied to a colloidal solution and electrophoresis is prevented?

(i) Reverse osmosis takes place.

(ii) Electroosmosis takes place.

(iii) Dispersion medium begins to move.

(iv) Dispersion medium becomes stationary.

Answer:

(ii) Electroosmosis takes place.

And

(iii) Dispersion medium begins to move.

Question: 36. In a reaction, catalyst changes ____________.

(i) physically

(ii) qualitatively

(iii) chemically

(iv) quantitatively

Answer:

(i) physically

And

(ii) qualitatively

Question: 37. Which of the following phenomenon occurs when a chalk stick is dipped in ink?

(i) adsorption of coloured substance

(ii) adsorption of solvent

(iii) absorption and adsorption both of solvent

(iv) absoprtion of solvent

Answer:

(i) adsorption of coloured substance

And

(iv) absoprtion of solvent

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