CUET Chemistry MCQs Unit V Surface Chemistry

Question : The colloid is :

(a) urea          

(b) blood

(c) cane sugar

(d) NaCl

Answer : B

Question :  Which of the following statements is not correct ?

(a) Physical adsorption is due to van der Waal’s forces

(b) Chemical adsorption first decreases with increase in temperature.

(c) Physical adsorption is reversible

(d) Adsorption energy for a chemical adsorption is generally greater than that of physical adsorption.

Answer : B

Question : The physical adsorption of gases on the solid surface is due to:

(a) Covalent bond

(b) Hydrogen bond

(c) Ionic bond

(d) Van der waal's forces

Answer : D 

Question : The movement of colloidal particles, under applied electric current is known as :

(a) electrodialysis 

(b) dialysis

(c) electrophoresis

(d) none of the above

Answer : C

Question : The density of gold is 19 g/cm³. If 1.9 × 10^–4 g of gold is dispersed in one litre of water to give a sol having spherical gold particles of radius 10 nm, then the number of gold particles per mm³ of the sol will be

(a) 1.9 × 10¹²

(b) 6.3 × 10¹⁴

(c) 6.3 × 10¹⁰

(d) 2.4 × 10⁶

Answer : D 

Question : Gold numbers of protective colloids A, B, C and D are 0.50, 0.01, 0.10 and 0.005, respectively. The correct order of their protective powers is 

(a) D < A < C < B

(b) C < B < D < A
(c) A < C < B < D

(d) B < D < A < C

Answer : C

Question :  Adsorption is always

(a) endothermic

(b) exothermic

(c) exothermic in case of physical and endothermic in case of chemical

(d) Either (a) or (b)

Answer : B

Question :  Adsorption of gases on solid surface is exothermic reaction because

(a) free energy increases

(b) enthalpy is positive

(c) entropy increases 

(d) enthalpy is negative

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 :  Which of the following is an example of absorption ?

(a) Water on silica gel .

(b) Water on calcium chloride.

(c) Hydrogen on finely divided nickel.

(d) Oxygen on metal surface.

Answer : B

Question :  If dispersed phase is a liquid and the dispersion medium is a solid, the colloid is known as

(a) a sol         

(b) a gel

(c) an emulsion  

(d) a foam

Answer : B

Question :  The role of a catalyst in a reversible reaction is to

(a) increase the rate of forward reaction

(b) decrease the rate of backward reaction

(c) alter the equilibrium constant of the reaction

(d) allow the equilibrium to be achieved quickly 

Answer : D 

Question :  Which of the following kind of catalysis can be explained by the adsorption theory ?

(a) Homogeneous catalysis

(b) Acid - base catalysis

(c) Heterogeneous catalysis

(d) Enzyme catalysis

Answer : C

Question :  A catalyst can affect reversible reaction by

(a) changing equilibrium constant

(b) slowing forward reaction

(c) attaining equilibria in both directions

(d) None of these 

Answer : C

Question :  Hydrolysis of urea is an example of

(a) homogenous catalysis

(b) heterogenous catalysis

(c) biochemical catalysis 

(d) zeolite catalysis 

Answer : C

Question :  Milk is a colloid in which a

(a) liquid is dispersed in a liquid

(b) solid is dispersed in a liquid

(c) gas is dispersed in a liquid

(d) sugar is dispersed in a liquid 

Answer : A 

Question :  An example of dispersion of a liquid in a gas is :

(a) milk

(b) vegetable oil

(c) foam 

(d) mist

Answer : D 

Question : The electrical charge on a colloidal particle is observed by:

(a) Ultramicroscope

(b) Scattering

(c) Brownian movement

(d) Electrophoresis

Answer : D 

Question : The size of colloidal particle is

(a) 10–3 to 10–9 m

(b) 10–3 to 10–12 m

(c) 10–6 to 10–9 m

(d) 10–12 to 10–19 m

Answer : C

Question :  Adsorbed acetic acid on activated charcoal is:

(a) adsorber

(b) absorber

(c) adsorbent 

(d) adsorbate

Answer : D 

Question :  The gas which is least adsorbed on charcoal (under identical conditions) is

(a) HCl 

(b) O₂

(c) CO₂ 

(d) NH₃

Answer : B

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

(a) High pressure

(b) Negative △H

(c) Higher critical temperature of adsorbate

(d) High temperature

Answer : D 

Question :  Hair cream is an example of

(a) gel

(b) sol

(c) aerosol 

(d) foam

Answer : D 

Question :  Which of the following is related to adsorption?

(i) △H = – ve (ii) △S = – ve

(iii) –T△S = – ve (iv) △G = – ve

(a) (i), (ii) and (iv) 

(b) (ii) and (iii)

(c) (iii) only

(d) (i), (iii) and (iv) 

Answer : A 

Question :  Which one of the following is an example of homogeneous catalysis ?

(a) Haber’s process of synthesis of ammonia

(b) Catalytic conversion of SO₂ to SO₃ in contact process

(c) Catalytic hydrogenation of oils

(d) Acid hydrolysis of methyl acetate. 

Answer : D 

Question :  What is the role of molybdenum in Haber’s process for manufacture of ammonia?

(a) As catalytic poison 

(b) As a catalytic promoter

(c) As a catalyst

(d) As a reactant 

Answer : B

Question :  An aerosol is a :

(a) dispersion of a solid or liquid in a gas

(b) dispersion of a solid in a liquid

(c) dispersion of a liquid in a liquid

(d) solid solution 

Answer : A 

Question : Purple of cassius is colloidal solution of :

(a) Silver

(b) Lead

(c) Gold 

(d) Mercury

Answer : C

Question : Which of the following is a lyophobic colloidal solution ?

(a) Aqueous starch solution

(b) Aqueous protein solution

(c) Gold solution

(d) Polymer solvent in some organic solvents

Answer : C

Question : The disease kala azar is caused by

(a) colloidal antimony

(b) milk of magnesia

(c) argyrols

(d) colloidal gold

Answer : A 

Question :  Adsorption due to strong chemical forces is called

(a) Chemisorption 

(b) Physisorption

(c) Reversible adsorption

(d) Both (b) and (c)

Answer : A 

Question :  The term ‘sorption’ stands for ___________.

(a) absorption

(b) adsorption

(c) both absorption and adsorption

(d) desorption

Answer : C

Question :  In Freundlich adsorption isotherm, the value of 1/n is :

(a) between 0 and 1 in all cases

(b) between 2 and 4 in all cases

(c) 1 in case of physical adsorption

(d) 1 in case of chemisorption 

Answer : A 

Question :  Alloy is an example of

(a) gel

(b) solidified emulsion

(c) solid solution 

(d) sol

Answer : C

Question :  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 centres of the catalyst becomes high due to strong 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 

Answer : A 

Question :  The efficiency of an enzyme in catalysing a reaction is due to its capacity

(a) to form a strong enzyme-substrate complex

(b) to decrease the bond energies of substrate molecule

(c) to change the shape of the substrate molecule

(d) to lower the activation energy of the reaction

Answer : D 

Question :  The size of colloidal particles is between

(a) 10^–7 – 10^–9 cm

(b) 10^–9 – 10^–11 cm

(c) 10^–5 – 10^–7 cm 

(d) 10^–2 – 10^–3 cm 

Answer : C

Question : Milk is colloid in which :

(a) Liquid is dispersed in liquid

(b) Gas is dispersed in liquid

(c) Sugar is dispersed in water

(d) Solid is dispersed in liquid

Answer : A 

Question :  How many layers are adsorbed in chemical adsorption ?

(a) One 

(b) Two

(c) Many

(d) Zero

Answer : A 

Question :  Choose the incorrect statement in respect of physisorption?

(a) It is not specific in nature

(b) It arises because of van der Waal’s force

(c) It is reversible in nature

(d) Enthalpy of adsorption is in the range 80-240 kJ mol^–1

Answer : D 

Question :  The adsorption of a gas on a solid surface varies with pressure of the gas in which of the following manner

(a) Fast → slow → independent of the pressure

(b) Slow → fast → independent of the pressure

(c) Independent of the pressure → fast → slow

(d) Independent of the pressure → slow → fast

Answer : A 

Question :  A catalyst :

(a) lowers the activation energy

(b) changes the rate constant

(c) changes the product

(d) itself destroyed in the reaction 

Answer : A 

Question :  A biological catalyst is

(a) an enzyme 

(b) a carbohydrate

(c) an amino acid

(d) a nitrogenous base 

Answer : A 

Question :  Butter is a colloid formed when

(a) Fat is dispersed in water

(b) Fat globules are dispersed in water

(c) Water is dispersed in fat

(d) None of the above 

Answer : C

Question : Lyophilic colloids are stable due to:

(a) Small size of the particle

(b) Large size of the particle

(c) Layer of dispersion medium on the particle

(d) Charge on the particle

Answer : C

Question : Which one of the following impurities present in colloidal solution cannot be removed by electrodialysis?

(a) Sodium chloride

(b) Potassium sulphate

(c) Urea

(d) Calcium chloride

Answer : C

Question :  Adsorption is accompanied by

(a) decrease in enthalpy and increase in entropy

(b) increase in enthalpy and increase in entropy

(c) decrease in enthalpy and decrease in entropy

(d) increase in enthalpy and decrease in entropy

Answer : C

Question :  For adsorption of a gas on a solid, the plot of log x/m vs log P is linear with slope equal to (n being whole number)

(a) k      

(b) log k

(c) n      

(d) 1/n

Answer : D 

Question :  Catalytic poisons act by :

(a) making the products chemically inactive.

(b) increasing the rate of the backward reaction.

(c) chemical combination with any one of the reactants.

(d) preferential adsorption on the catalyst surface. 

Answer : D 

Question :  The action of enzymes in living system is to :

(a) supply energy to tissues

(b) enhance immunity

(c) circulate oxygen

(d) enhance the rate of biochemical reactions.

Answer : D 

Question : A catalyst

(a) changes the equilibrium constant

(b) lowers the activation energy

(c) increases the forward and backward reactions at different speeds.

(d) follows same mechanism for the reaction.

Answer : B

Question :  Which is not correct regarding the physical adsorption of a gas on surface of solid ?

(a) On increasing temperature, adsorption increases continuously

(b) Enthalpy and entropy changes are negative

(c) Adsorption is more for some specific substance

(d) Reversible

Answer : A 

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

(a) decrease in temperature

(b) increase in temperature

(c) increase in surface area of adsorbent

(d) decrease in surface area of adsorbent

Answer : B

Question :  Active charcoal is a good catalyst because it

(a) is made up of carbon atoms.

(b) is very reactive.

(c) has more adsorption power.

(d) has inert nature toward reagents. 

Answer : C

Question :  Which of the following step(s) is/are not involved in the mechanism of adsorption theory of heterogeneous catalyst?

(i) Diffusion of reactants to the surface of the catalyst.

(ii) Sorption of reactant molecules on the surface of the catalyst.

(iii) Occurrence of chemical reaction on the catalyst’s surface through formation of an intermediate.

(iv) Desorption of reaction products from the catalyst’s surface.

(v) Diffusion of reaction products away from the catalyst’s surface.

(a) (i) only

(b) (ii) and (iv)

(c) (ii) only 

(d) (i), (ii) and (v)

Answer : C

Question : Preparation of Lyophobic sols by chemical method involves

(a) double decomposition

(b) oxidation & reduction

(c) hydrolysis

(d) all of these

Answer : D 

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

(a) involved van der Waal’s 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 :  Catalyst increases the rate of reaction by

(a) decreasing threshold energy

(b) decreasing activation energy

(c) increasing activation energy

(d) decreasing equilibrium constant 

Answer : B

Question : Which of the following electrolyte will have maximum flocculation value for Fe(OH)₃ sol?

(a) NaCl         

(b) Na₂S
(c) (NH₄)₃PO₄

(d) K₂SO₄

Answer : A 

Question :  Extent of physisorption of a gas increases with _______.

(a) increase in temperature.

(b) decrease in temperature.

(c) decrease in surface area of adsorbent.

(d) decrease in strength of van der Waal’s forces.

Answer : B

Question :  Identify the correct statement regarding enzymes

(a) Enzymes are specific biological catalysts that cannot be poisoned.

(b) Enzymes are normally heterogeneous catalysts that are very specific in their action.

(c) Enzymes are specific biological catalysts that can normally function at very high temperatures (T ≈ 1000K).

(d) Enzymes are specific biological catalysts that possess well-defined active sites. 

Answer : D 

Question : Choose the correct option

Assertion: A catalyst is more effective in finely divided form.

Reason: Finely divided form has more surface area. 

(a) If both Assertion and Reason are correct and the Reason is a correct explanation of the Assertion.

(b) If both Assertion and Reason are correct but Reason is not a correct explanation of the Assertion.

(c) If the Assertion is correct but Reason is incorrect.

(d) If both the Assertion and Reason are incorrect.

Answer : A 

Question :  Which is adsorbed in maximum amount by activated charcoal ?

(a) N₂       

(b) CO₂

(c) Cl₂      

(d) O₂

Answer : B

Question :  Which is not correct regarding the adsorption of a gas on surface of solid?

(a) On increasing temperature, adsorption increases continuously

(b) Enthalpy and entropy changes are –ve

(c) Adsorption is more for some specific substance

(d) This Phenomenon is reversible

Answer : A 

Question :  In physical adsorption, gas molecules are bound on the solid surface by

(a) chemical forces

(b) electrostatic forces

(c) gravitational forces 

(d) van der Waal’s forces

Answer : D 

Question :  According to Freundlich adsorption isotherm, the amount of gas adsorbed at very high pressure

(a) reaches a constant limiting value

(b) goes on increasing with pressure

(c) goes on decreasing with pressure

(d) increase first and decreases later with pressure

Answer : B