Chapter 11

Adsorption of gases on solid surface is generally exothermic because (a) enthalpy is positive (b) entropy decreases (c) entropy increases (d) free energy increases

Which of the following is true in respect of adsorption? (a) \(\Delta \mathrm{G}<0 ; \Delta \mathrm{S}>0 ; \Delta \mathrm{H}<0\) (b) \(\Delta \mathrm{G}<0 ; \Delta \mathrm{S}<0 ; \Delta \mathrm{H}<0\) (c) \(\Delta \mathrm{G}>0 ; \Delta \mathrm{S}>0 ; \Delta \mathrm{H}<0\) (d) \(\Delta \mathrm{G}<0 ; \Delta \mathrm{S}<0 ; \Delta \mathrm{H}>0\)

Which of the following is true in respect of adsorption? (a) \(\Delta \mathrm{G}<0 ; \Delta \mathrm{S}>0 ; \Delta \mathrm{H}<0\) (b) \(\Delta \mathrm{G}<0 ; \Delta \mathrm{S}<0 ; \Delta \mathrm{H}<0\) (c) \(\Delta \mathrm{G}>0 ; \Delta \mathrm{S}>0 ; \Delta \mathrm{H}<0\) (d) \(\Delta \mathrm{G}<0 ; \Delta \mathrm{S}<0 ; \Delta \mathrm{H}>0\)

Langmuir's adsorption equation which describes the amount of gas adsorbed on a solid surface is written as \(\frac{\mathrm{p}}{\mathrm{x} / \mathrm{m}}=\frac{1}{\mathrm{ab}}+\frac{\mathrm{p}}{\mathrm{b}}\) Here \(\mathrm{x} / \mathrm{m}\) is the extent of adsorption, a and \(\mathrm{b}\) are constants, and \(\mathrm{p}\) is the gas pressure. On the basis of the above equation indicate which of the following statements is correct? (1) At low value of p, \(\mathrm{x} / \mathrm{m} \propto \mathrm{p}\). (2) At high value of \(\mathrm{p}, \mathrm{x} \longrightarrow \mathrm{b}\) (adsorption is independent of pressure). (3) Between the low and high value of \(\mathrm{p}\), the above equation becomes \(\mathrm{x} / \mathrm{m}=\mathrm{kp}^{1 / \mathrm{n}}\), which is the Freundlich equation (here \(\mathrm{k}\) and \(\mathrm{n}\) are constants) (a) 1 and 2 (b) 2 and 3 (c) 1 and 3 (d) 1,2 and 3

What is the correct sequence of the increasing effectiveness of the following electrolyte for the coagulation of ferric hydroxide sol? 1\. \(\mathrm{K}_{4}\left[\mathrm{Fe}(\mathrm{CN})_{6}\right]\) 2\. \(\mathrm{AlPO}_{4}\) 3\. \(\mathrm{CaSO}_{4}\) 4\. \(\mathrm{SnCl}_{4}\) Select the correct answer using the codes given below: (a) \(4,2,1,3\) (b) \(4,3,2,1\) (c) \(1,2,3,4\) (d) \(3,4,2,1\)

Which of the following statements are correct? (1) Electro-osmsis is the movement of the particles of dispersion medium under the influence of an electric field. (2) On the application of an electric field, the particles of a lyophobic sol may move in either direction or not move at all. (3) Surface tension of lyophobic sols is similar to that of the dispersion medium. (a) 1 and 2 (b) 1 and 3 (c) 2 and 3 (d) 1,2 and 3

Which of the following statements are correct? (1) The smaller the gold number of a lyophilic colloid, the larger will be its protective power. (2) Lyophilic sols in contrast to lyophobic sols, are easily coagulated on addition of small amounts of electrolytes. (3) Ferric chloride solution is used to stop bleeding from a fresh cut because it coagulates blood. (4) The flocculation value of arsenious sulphide sol is independent of the anion of the coagulating electrolyte. Select the correct answer using the codes given below: (a) 1,2 and 4 (b) 1,2 and 3 (c) 1,3 and 4 (d) 2,3 and 4

On breaking a cubic solid (edge \(=1 \mathrm{~m}\) ) into fine cubic particles of edge \(1 \mu \mathrm{m}\) surface becomes (a) remains same (b) 100 times (c) 1000 times (d) 1000,000 times

The adsorption of a gas, on a solid surface, varies with pressure of the gas in which of the following manner? (a) slow \longrightarrow fast \(\longrightarrow\) independent of the pressure (b) fast \(\longrightarrow\) slow \(\longrightarrow\) independent of the pressure (c) independent of the pressure \(\longrightarrow\) slow \(\longrightarrow\) fast (d) independent of the pressure \(\longrightarrow\) fast \(\longrightarrow\) slow

Lyophilic sols are more stable than lyophobic sols because the particles (1) are positively charged (2) are negatively charged (3) are solvated (4) repel each other (5) are heavy (a) 2,3 and 4 (b) 2 and 3 (c) 1,2 and 5 (d) 3 only

Potassium stearate is obtained by the saponification of an oil or fat. It has the formula \(\mathrm{CH}_{3}-\left(\mathrm{CH}_{2}\right)_{16}-\mathrm{COO}^{-} \mathrm{K}^{+} .\)The molecule has a lyopho- bic end \(\left(\mathrm{CH}_{3}\right)\) and a lyophilic and \(\mathrm{COO}^{-} \mathrm{K}^{+}\). Potassium stearate is an example of (1) lyophobic colloid (2) associated colloid or micelle (3) multimolecular colloid (4) macromolecular colloid (a) 2 only (b) 1 and 2 (c) 3 and 4 (d) 4 only

Which of the following factors are responsible for the increase in the rate of a surface catalysed reaction? 1\. A catalyst provides proper orientation for the reactant molecules to react. 2\. Heat of adsorption of reactants on a catalyst helps reactant molecules to overcome activation energy. 3\. The catalyst increases the activation energy of the reaction. 4\. Adsorption increases the local concentration of reactant molecules on the surface of the catalyst. Select the correct answer using the code given below: (a) 1 and 2 (b) 1 and 3 (c) 2,3 and 4 (d) 1,2 and 4 .

Choose the incorrect statement for chemical adsorption (1) value of adsorption enthalpy is above \(-20.0 \mathrm{kJmol}^{-1}\) (2) van der Waals forces exist between the adsorbent and the adsorbate (3) usually monomolecular layer is formed on the adsorbent (4) multimolecular layer may be formed on the adsorbent (a) 1,2 and 3 (b) 2,3 and 4 (c) 1,2 and 4 (d) \(1,2,3\) and 4

Which of the following process does not occur at the interface of phases (a) Hetergenous catalysis (b) Homogeneous catalysis (c) Corrosion (d) Crystallisation

Which of the following interface cannot be obtained? (a) Solid-liquid (b) Liquid-liquid (c) Liquid-gas (d) Gas-gas

The term soption stands for (a) Adsorption (b) Absorption (c) Desorption (d) Both absorption and adsorption

Extent of physisorption of a gas increases with (a) Increase in temperature (b) Decrease in temperature (c) Decrease in strength of van der Walls forces (d) Decrease in surface area of adsorbent.

Extent of adsorption of adsorbate from solution phase increases with (a) Decrease in surface area of adsorbent (b) Increase in temperature or solution (c) Increase in amount of adsorbate in solution (d) Decrease in amount of adsorbate in solution

Which one of the following is not applicable to the phenomenon of adsorption? (a) \(\Delta \mathrm{G}<0\) (b) \(\Delta \mathrm{S}<0\) (c) \(\Delta \mathrm{H}<0\) (d) \(\Delta H>0\)

Which of the following is not a favourable condition for physical adsorption? (a) Negative \(\Delta \mathrm{H}\) (b) High pressure (c) High temperature (d) Higher critical temperature of adsorbate

Physical adsorption of a gaseous species may change to chemical adsorption with (a) Increase in temperature (b) Decrease in temperature (c) Decrease in surface area of adsorbent (d) Increase in surface area of adsorbent

In physisorption adsorbent does not show specificity for any particular gas because (a) Enthalpy of adsorption is low (b) It is a reversible process (c) Gases involved behave like ideal gases (d) Involved van der Waals forces are universal.

Which of the following is an example of absorption? (a) Oxygen on metal surface (b) Hydrogen on finely divided nickel (c) Water on calcium chloride (d) Water on silica gel

On the basis of data given below predict which of the following gases shows least adsorption on a definite amount of charcoal? \(\begin{array}{lllll} \text { Gas } & \mathrm{CO}_{2} & \mathrm{SO}_{2} & \mathrm{CH}_{4} & \mathrm{H}_{2} \\ \text { Critical temp./K } & 304 & 630 & 190 & 33 \end{array}\) (a) \(\mathrm{SO}_{2}\) (b) \(\mathrm{CH}_{4}\) (c) \(\mathrm{H}_{2}\) (d) \(\mathrm{CO}_{2}\)

In which of the following reactions heterogenous catalysis is involved? (i) \(2 \mathrm{SO}_{2}(\mathrm{~g})+\mathrm{O}_{2}(\mathrm{~g}) \stackrel{\mathrm{No}(\mathrm{g})}{\longrightarrow} 2 \mathrm{SO}_{3}(\mathrm{~g})\) (ii) \(2 \mathrm{SO}_{2}(\mathrm{~g}) \stackrel{\mathrm{Pt}(\mathrm{S})}{\longrightarrow} 2 \mathrm{SO}_{3}(\mathrm{~g})\) (iii) \(\mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \stackrel{\mathrm{Fe}(\mathrm{S})}{\longrightarrow} 2 \mathrm{NH}_{3}(\mathrm{~g})\) (iv) \(\mathrm{CH}_{3} \mathrm{COOCH}_{3}(\mathrm{I})+\mathrm{H}_{2} \mathrm{O}(\mathrm{I}) \stackrel{\mathrm{HCl}(\mathrm{l})}{\longrightarrow} \mathrm{CH}_{3} \mathrm{COOH}\) \(+(\) aq \()+\mathrm{CH}_{3} \mathrm{OH}(\mathrm{aq})\) (a) (ii), (iii) (b) (ii), (iii), (iv) (c) (i), (ii), (iii) (d) (iv)

At high concentration of soap in water, soap behaves as (a) Molecular colloid (b) Lyophilic colloid (c) Macromolecular colloid (d) Associated colloid

Which of the following will show Tyndall effect? (a) Aqueous solution of soap above critical micelle concentration (b) Aqueous solution of soap below critical micelle concentration (c) Aqueous solution of sugar (d) Aqueous solution of sodium chloride

Method by which lyophobic sol can be protected. (a) By addition of an electrolyte (b) By addition of oppositely charged sol. (c) By addition of lyophilic sol. (d) By bhoiling

Freshly prepared precipitate sometimes gets converted to colloidal solution by (a) Electrolysis (b) Coagulation (c) Peptisation (d) Diffusion

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) Emulsion (c) Sol (d) Gel

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) Remain suspended in the dispersion medium (b) Form lyophilic colloids (c) Are comparatively less in number (d) Exhibit enormous surface area

Which of the following process is responsible for the formation of delta at a place where rivers meet the sea? (a) Coagulation (b) Peptisation (c) Emulsification (d) Colloid formation

Which of the following process is not responsible for the presence of electric charge on the sol particles? (a) Adsorption of ionic species from solution (b) Electron capture by sol particles (c) Absorption of ionic species from solution (d) Formation of Helmholtz electrical doable layer.

A catalyst (a) Increases the frequency of collision of reacting species. (b) Alters the reaction mechanism. (c) Decreases the activation energy (d) Increases the average kinetic energy of the reacting molecules.

Identify the wrong statements. (a) On dissolving a detergent in water, its surface tension is increased. (b) Phenol and benzoic acid can be distinguished using \(\mathrm{NaOH}\) aqueous solution. (c) Langmuir adsorption theory explains chemical adsorption. (d) Valence bond theory of complexes explain the colour of complexes.

Which among the following are lyophilic in nature? (a) Gold (b) Gum (c) Starch (d) Gelatin

Emulsion can be destroyed by (a) The addition of an emulsifier which tends to form an emulsion of the same type. (b) Freezing (c) Electrophoresis with a high potential (d) All of these

Which forms multi-layers during adsorption? (a) Van der Waal's adsorption (b) Chemical adsorption (c) Physical adsorption (d) All of these

Which of the following options are correct? (a) Micelle formation by soap in aqueous solution occurs above a particular concentration (b) Micelle formation by soap in aqueous solution is possible at all temperatures. (c) Soap solution behaves as a normal strong electrolyte at all concentrations. (d) On dilution of soap solution micelles may revert to individuals ions.

Which of the following statements are correct about solid catalyst? (a) Catalyst is required in large quantities to catalyse reactions. (b) Catalytic activity of a solid catalyst does not depend upon the strength of chemisorptions (c) Same reactants may give different product by using different catalysts. (d) Catalyst does not change \(\Delta \mathrm{H}\) of reaction.

Freundlich adsorption isotherm is given by expression \(\frac{x}{m}=k p^{\frac{1}{n}}\) which of the following conclusions can be drawing from this expression (a) When \(\frac{1}{\mathrm{n}}=0\), the adsorption is independent of pressure. (b) When \(\frac{1}{n}=0\), the adsorption is independent of pressure. (c) When \(\mathrm{n}=0\), plot of \(\frac{\mathrm{x}}{\mathrm{m}} \mathrm{Vs} \mathrm{p}\) is a curve. (d) When \(\mathrm{n}=\mathrm{m} 0, \frac{\mathrm{x}}{\mathrm{m}}\) Vs p graph is a line paralle to \(\mathrm{x}\) axis.

\(\mathrm{H}_{2}\) gas is adsorbed on activated charcoal to a very little extend in comparison to easily liquefiable gases due to (a) Very strong van der Waal's interaction (b) Very high critical temperature (c) Very low critical temperature (d) Very weak van der Waals forces

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

An emulsion cannot be broken by and (a) Adding more amount of dispersion medium (b) Heating (c) Adding emulsifying agent (d) Freezing

Which of the following substances will precipitate the negatively changed emulsions? (a) Glucose (b) Urea (c) \(\mathrm{NaCl}\) (d) \(\mathrm{KCl}\)

Which of the following colloids cannot be coagulaten easily? (a) Reversible colloids (b) Lyophillic colloids (c) Irreversible colloids (d) Lyophobic colloids

What happens when a lyophilic sol is added to a lyophobic sol? (a) Lyophilic sol is protected (b) Film of lyophobic sol is formed over lyophilic sol (c) Lyophobic sol is protected (d) Film of lyophltic sol is formed over lyophobic sol.

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

In a reaction, catalyst changes (a) Qualitatively (b) Physically (c) Quantitatively (d) Chemically

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