Chapter 9

Which one of the following characteristics is not correct for physical adsorption? (a) Adsorption on solids reversible (b) Adsorption increases with the increase in temperature (c) Adsorption is spontaneous (d) Both enthalpy and entropy of adsorption are negative

Milk is an emulsion in which (a) A liquid is dispersed in a liquid (b) A solid is dispersed in a liquid (c) A gas is dispersed in a liquid (d) Lactose is dispersed in a liquid

Which of the following sols is negatively charged? (a) Arsenious sulphide (b) Aluminum hydroxide (c) Ferric hydroxide (d) Silver iodide in silver nitrate solution

Spontaneous adsorption of a gas on a solid surface is an exothermic process because (a) \(\Delta H\) for the system increases (b) \(\triangle S\) for the gas increases (c) \(\triangle S\) for the gas decreases (d) \(\Delta G\) for the gas incrao

Which of the following gas is adsorbed most by activated charcoal? (a) \(\mathrm{CO}_{2}\) (b) \(\mathrm{N}_{2}\) (c) \(\mathrm{CH}_{4}\) (d) \(\mathrm{Ar}\)

Fog is an example of a colloid system of (a) Liquid particles dispersed in gas (b) Gas particles dispersed in gas (c) Solid particles dispersed in gas (d) Solid particles dispersed in liauid

If the dispersed phase is a solid and the dispersion medium is a liquid, the colloid is known as (a) an emulsion (b) a gel (c) a solid foam (d) a sol

During adsorption (a) \(T \Delta S\) is positive (b) \(\Delta H-T \Delta S\) is negative (c) \(\triangle H\) is positive (d) \(T \triangle S\) and \(\Delta G\) become zero

Freundlich adsorption isotherm gives a straight line on plotting (a) \(x / m\) vs \(P\) (b) \(\log x / m\) vs \(P\) (c) \(\log x / m\) vs \(\log P\) (d) \(x / m\) vs \(l / P\)

The volume of gases \(\mathrm{H}_{2}, \mathrm{CH}_{4}, \mathrm{CO}_{2}\) and \(\mathrm{NH}_{3}\) absorbed by \(1 \mathrm{~g}\) of charcoal at \(288 \mathrm{~K}\) are in the order (a) \(\mathrm{H}_{2}>\mathrm{CH}_{4}>\mathrm{CO}_{2}>\mathrm{NH}_{3}\) (b) \(\mathrm{CH}_{4}>\mathrm{CO}_{2}>\mathrm{NH}_{3}>\mathrm{H}_{2}\) (c) \(\mathrm{CO}_{2}>\mathrm{NH}_{3}>\mathrm{H}_{2}>\mathrm{CH}_{4}\) (d) \(\mathrm{NH}_{3}>\mathrm{CO}_{2}>\mathrm{CH}_{1}>\mathrm{H}_{2}\)

Hardy-Schulze law states that (a) Larger the size of the coagulating ions, greater is the coagulating power, having opposite sign of solution (b) Solution must have zero gold number (c) Disperse phase and dispersion medium must be of the same sign (d) Micelles coagulate in the presence of surfactants

The blue colour of the sky is due to (a) scattering of light from particles of dust in the atmosphere (b) scattering of light from the sun (c) scattering of light due to the ozone layer (d) all of these

The coagulating power of an effective ion carrying the charge opposite to the sol particles is given by (a) Brownian movement (b) Gold number (c) Tyndall effect (d) Hardy-Schulze law

On adding few drops of dilute HCl to freshly precipitated ferric hydroxide, a red coloured colloidal solution is obtained. This phenomenon is known as (a) Peptization (b) Dialysis (c) Protective action (d) Dissolution

Zeta potential (or electrokinetic potential) is the (a) potential required to bring about coagulation of a colloidal sol (b) potential required to give the particles a speed of \(1 \mathrm{~cm} / \mathrm{s}\) in the sol (c) potential difference between fixed charged layer and diffused layer having opposite charge (d) potential energy of the colloidal particles

Which of the following statements is correct for a lyophilic sol? (a) It is not easily solvated. (b) It carries charges. (c) The coagulation of this sol is irreversible in nature. (d) It is quite stable in a solvent.

The isoelectric point of colloidally dispersed material is the \(\mathrm{pH}\) value at which (a) the dispersed phase migrates in an electric field (b) the dispersed phase does not migrate in an electric field (c) the dispersed phase has \(\mathrm{pH}\) equal to 7 (d) the dispersed phase has \(p \mathrm{H}\) equal to zero

Adsorption is accompanied by the evolution of heat. So acconding to Le- Chatelier principle the amount of substance adsorbed should (a) increase with decrease in temperature (b) increase with increase in temperature (c) decrease with decrease in temperature (d) decrease with decrease in temperature

The critical micelle concentration \((\mathrm{CMC})\) is (a) the concentration at which micellization starts (b) the concentration at which the true solution is formed (c) the concentration at which one molar electrolyte is present per \(1000 \mathrm{~g}\) of the solution (d) the concentration at which \(\Delta H=0\)

An emulsifier is a substance which (a) stabilizes the emulsion (b) homogenises the emulsion (c) coagulates the emulsion (d) accelerates the dispersion of liquid in liquid

The Rubin number which was proposed by Ostwald as an alternative to the Gold number in order to measure the protective efficiency of a lyophilic colloid may be defined as the (a) mass in milligrams of a colloid per \(100 \mathrm{c.c}\). of solution which just prevents the colour change of standard sol of dye Congo-Rubin from red to violet when \(0.16 \mathrm{~g}\) eq. \(\mathrm{KCl}\) is added to it. (b) mass in grams of a colloid per \(100 \mathrm{c.c}\). of solution which just prevents the colour change of standard sol of dye Congo-Rubin from red to violet when \(0.1 \mathrm{M}\) is added to it. (c) mass in grams of a colloid per \(100 \mathrm{c.c}\), of solution which just prevents the color change of standard sol of dye Congo-Rubin from red to violet when \(0.2 \mathrm{M} \mathrm{KCl}\) is added to it. (d) mass in grams of a colloid per 100 c.c. of solution which just prevents the color change of standard sol of dye Congo-Rubin from red to violet when \(1 \mathrm{M} \mathrm{KCl}\) is added to it.

A colloidal solution is subjected to an electrical field. The particles move towards anode. The coagulation of same sol is studied using \(\mathrm{NaCl}, \mathrm{BaCl}_{2}\) and \(\mathrm{AICl}_{3}\) solutions, Their coagulating power should be (a) \(\mathrm{NaCl}>\mathrm{BaCl}_{2}>\mathrm{AlCl}_{3}\) (b) \(\mathrm{BaCl}_{2}>\mathrm{AlCl}_{3}>\mathrm{NaCl}\) (c) \(\mathrm{A} \mathrm{Cl}_{3}>\mathrm{BaCl}_{2}>\mathrm{NaCl}\) (d) \(\mathrm{BaCl}_{2}>\mathrm{NaCl}>\mathrm{AlCl}_{3}\)

Random motion of colloid particle is known as (a) Dialysis (b) Brownian movement (c) Electro-osmosis (d) Tyndall effect

In the hydrogenation of oils the catalyst used is (a) Iron (b) Platinum (c) Nickel (d) Molybdenum

Rate of physisorption increases with (a) decrease in temperature (b) increase in temperature (c) decrease in pressure (d) decrease in surface area

Adsorption of gases on solid surface is generally exothermic because (a) Enthalpy is positive (b) Entropy decreases (c) Entropy increases (d) Free energy increases

Chergy increases Pick out the one which does not belong to the family of enzymes (a) Lipase (b) Pepsin (c) Ptylin (d) Cellulose

(d) Cellulose Which of the following forms cationic micelles above certain concentration? (a) Sodium dodecyl sulphate (b) Sodium acetate (c) Urea (d) Cetyltrimethyl ammonium

y ammonium bromide Which of the following will have the highest coagulation power for \(\mathrm{As}_{2} \mathrm{~S}_{3}\) colloids? (a) \(\mathrm{PO}_{4}^{3}{\underline{\phantom{xx}}}^{3}\) (b) \(\mathrm{SO}_{4}^{2}\) (c) \(\mathrm{Al}^{3+}\) (d) \(\mathrm{Na}^{+}\)

According to the adsorption theory of catalysis, the speed of the reaction increases because (a) adsorption lowers the activation energy of the reaction. (b) the concentration of reactant molecules at the active centers of the catalyst becomes high due to adsorption. (c) in the process of adsorption, the activation energy of the molecules becomes large. (d) adsorption produces heat which increases the speed of the reaction.

fcaction. Alum helps in purifying water by (a) forming Si complex with clay particies. (b) sulphate part which combines with dirt and removes it. (c) aluminum which coagulates the mud particle. (d) making mud water-soluble.

Identify the correct statement regarding enzymes? (a) Enzymes are specific biological catalysts that can normally function at very high temperature \((T-1000 \mathrm{~K})\). (b) Enzymes are specific biological catalysts that possess well defined active sites. (c) Enzymes are specific biological catalysts that cannot be poisoned. (d) Enzymes are normally heterogenous catalysts that are very specific in their action.