CBSE Questions for Class 12 Engineering Chemistry Surface Chemistry Quiz 10 - MCQExams.com

According to adsorption theory of catalysis, the reaction rate increase, because
  • Adsorption produces heat which increases the rate of reaction.
  • In the process of adsorption, the kinetic energy of the molecules increases.
  • The concentration of reactants at the active centres becomes high due to adsorption.
  • The activation energy of the reaction becomes high due to adsorption.
Which of the following acts as negative catalyst?
  • Tetraethyl lead as antiknock compound
  • Glycerol in decomposition of $$H_{2}O_{2}$$
  • Ethanol in the oxidation of chloroform
  • Lindlar's catalyst
The dispersed phase in colloidal iron(III) hydroxide and colloidal gold is positively and negatively charged, respectively. Which of the following statement(s) is/are not correct?
  • Magnesium chloride solution coagulates the gold sol more readily than the iron(III) hydroxide sol.
  • Sodium sulphate solution causes coagulation in both sols.
  • Mixing of the sols has no effect.
  • Coagulation in both sols can be brought about by electrophoresis.
Sticking of one substance at the surface of another is called 
  • Absorption
  • Chemisorption
  • Adsorption
  • Desorption
Solid acts as an adsorbent because it has 
  • A definite shape
  • Small pores in it
  • Unsaturated valencies
  • A high lattice energy
A chemical reaction is catalyzed by a catalyst X . Hence X 
  • Reduces enthalpy of the reaction
  • Decrease rate constant of the reaction
  • Increases activation energy of the reaction
  • Does not affect equilibrium constant of reaction
Adsorption is multilayer in the case of 
  • Physical adsorption
  • Chemisorption
  • Both
  • None of both
Point out the wrong statement , Physical adsorption is characterised by 
  • Attraction due to weak van der Waal's forces
  • lrreversible nature of adsorption
  • Multimolecular adsorption layers
  • Decreases in adsorption with increase in temperature
Physical adsorption 
  • involves the weak attractive interaction between the adsorbent and adsorbate
  • involves the chemical interactions between the adsorbent and adsorbate
  • is irreversible in nature
  • increases with increases of temperature
In physical adsorption the gas molecules are held on solid surface by 
  • Chemical forces
  • Electrostatic forces
  • Gravitational forces
  • Vander waal's forces
Which of the following processes does not involve catalysis
  • Haber's process
  • Thermite process
  • Ostwald process
  • Contact process
A catalyst in a chemical reaction
  • Does not initiate a reaction
  • Increases the activation energy of the reaction
  • Changes the equilibrium constant of reaction
  • Dose not change the rate of the reaction
Gelatin is added to ice-creams.
  • As a coagulant
  • For taste
  • For colour
  • As a protective colloid
Sodium sterate forms in water
  • True solution
  • A suspencion
  • An emulsion
  • A colloidal solution
Which of the following statements about a catalyst is true 
  • It lowers the energy of activation
  • The catalyst altered during the reaction
  • It does not alter the equilibrium
  • All of these
Which one of the following statements is incorrect in the case of heterogeneous catalysis
  • The catalyst lower the energy activation
  • The catalyst actually forms a compound with the reactant
  • The surface of the catalyst plays a very important role
  • There is no change in the energy of activation
Regarding criteria of catalysis which one of the following statements is not true
  • the catalyst is unchanged chemically at the end of the equilibrium position
  • a small quantity of catalyst is sufficient to bring about a considerable amount of reaction
  • in a reversible the catalyst alters the equilibrium position
  • the catalyst accelerates the reaction
An emulsifier
  • Accelerates the dispresion
  • Homogenises the emulsion
  • Stabilizes the emulsion
  • Aids the flocculation of emulsion
Which of the following is an example of 'Water in oil' type emulsion
  • Butter
  • Milk
  • Cream
  • Face cream
Protons accelerate the hydrolysis of esters. This is an example of
  • A heterogeneous catalysis
  • An acid-base catalysis
  • A promoter
  • A negative catalyst
Emulsifier is mixed to
  • Increase the stability of emulsion
  • Decrease the stability of emulsion
  • Change oil into water like emulsion
  • None of these
Emulsifiers are generally
  • Soap
  • Synthetic detergents
  • Lyophilic sols
  • All of these
White of an egg is partly coagulated by heating which can be again obtained back by some pepsin and little HCl. This process is called
  • Peptization
  • Coagulation
  • Precipitation
  • None of these
In a homogeneous catalysis 
  • The catalyst and the reactants should be gases
  • The catalyst and the reactants should from a single phase
  • Catalyst and the reactants are all solids
  • The catalyst and the reactions are all liquids
A catalyst is a substance which
  • Increases the rate if reaction
  • Increases the amount of the products formed in a reaction
  • Decreases the temperature required for the reaction
  • Alters the speed of the reaction remaining unchanged chemically at the end of the reaction
A catalyst remains unchanged at the end of th reaction regarding 
  • Mass
  • Physical state
  • Physical state and chemical composition
  • Mass and chemical composition
Which of the following statement regarding catalyst is not true
  • A catalyst remains unchanged in composition and quantity at the end of the reaction
  • A catalyst does not alter the equilibrium in a reversible reaction
  • Catalyst are sometimes very specific in respect of reaction
  • Catalyst are sometimes very specific in respect of reaction
Which of the following statement is wrong
  • Catalysts can aid a rapid reaching of the equilibrium position, but do not change the position of the equilibrium
  • Homogeneous catalysis generally involves an equilibrium reaction between at least one of the reactants and the catalyst
  • Heterogeneous catalysis involves chemisorption on the surface of the catalyst
  • Positive catalysts raise the energy of activation of the reaction they catalyse
A cleared solution which is again converted into colloidal solution, the process is called
  • Peptisation
  • Electrolytic addition
  • Electrophoresis
  • None of these
Liquid - liquid sols are known as
  • Aerosols
  • Emulsions
  • Foam
  • Gel
Milk is an example of 
  • Pure solution
  • Emulsion
  • Gel
  • Suspension
Which of the following methods is used for the destruction of colloids
  • Dialysis
  • Condensation
  • By ultrafilteration
  • By adding electrolyte
Which one of the following characteristics is not correct for physical adsorption
  • Adsorption on solids is reversible
  • Adsorption increases with increase in temperature
  • Adsorption is spontaneous
  • Both enthalpy and entropy of adsorption are negative
Colloidal solutions of gold prepared by different methods have different colours owing to
  • The difference in the size of the colloidal particles
  • The fact that gold exhibhits a variable valency of +1 and +3
  • Different concentrations of gold
  • Presence of different types of forign particles depending upon the method of preperation of the colloid
$$ Fe(OH)_{3} $$ when treated with $$ Fe(OH)_{3} $$ solution a reddish-brown solution is formed. The process involved is
  • Dispersion
  • Exchange of solvent
  • Peptization
  • None of these
Physical adsorption is essentially quite appreciable
  • At room temperature
  • At higher temperature
  • At lower temperature
  • None of these
A catalyst is a substance which______________
  • is always in the same phase as in the reactants
  • alters the equilibrium in a reaction
  • does not participate in the reaction but alters the rate of reaction
  • participates in the reaction and provide an easier pathway for the same
The catalyst used for the polymerisation of olefins is:
  • Ziegler Natta catalyst
  • Wilkinsons catalyst
  • Pd-catalyst
  • Zeises salt catalyst
Colloidal solution of gold cannot be prepared by
  • Bredig's are method
  • Mechanical dispersion
  • Reduction of gold chloride
  • Exchange of solvents
Milk is an emulsion.
  • True
  • False
Milk is an emulsion. 
  • True
  • False
Which are not purely surface phenomena?
  • Adsorption , surface tension
  • Surface tension , viscosity
  • Adsorption , viscosity
  • Absorption , viscosity
A reaction is catalysed by $$H^{+}$$ ion. In the presence of an acid $$HA$$, the rate constant is $$2\times10^{-3}min^{-1}$$ and in the presence of an acid $$HB$$, the rate constant is $$1\times10^{-3}min^{-1}$$. Given $$HA$$ and $$HB$$ both being strong acids, we may conclude that:
  • equilibrium constant is 2
  • $$HA$$ is stronger acid than $$HB$$
  • relative strength of $$HA$$ and $$HB$$ is $$2$$
  • $$HA$$ is weaker acid than $$HB$$ and their relative strength is $$0.5$$
Which of the following metal sols cannot be prepared by Bredig's arc method?
  • Silver
  • Potassium
  • Gold
  • Platinum
Which of the following statement is incorrect regarding physisorption?
  • It occurs because of Van der Waals' forces.
  • More easily liquiefiable gases are adsorbed readily.
  • Under high pressure, it results into multi molecular layer on adsorbent surface.
  • Enthalpy of adsorption $$(\Delta \mathrm{H}_{\mathrm{a}\mathrm{d}\mathrm{s}\mathrm{o}\mathrm{r}\mathrm{p}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}})$$ is low and positive.
Among the following, the surfactant that will form micelles in aqueous solution at the lowest molar concentration at ambient conditions is :
  • $$\mathrm{C}\mathrm{H}_{3}(\mathrm{C}\mathrm{H}_{2})_{15}\mathrm{N}^{+}(\mathrm{C}\mathrm{H}_{3})_{3}\mathrm{B}\mathrm{r}^{-}$$
  • $$\mathrm{C}\mathrm{H}_{3}(\mathrm{C}\mathrm{H}_{2})_{11}\mathrm{O}\mathrm{S}\mathrm{O}_{3}^{-}\mathrm{N}\mathrm{a}^{+}$$
  • $$\mathrm{C}\mathrm{H}_{3}(\mathrm{C}\mathrm{H}_{2})_{6}\mathrm{C}\mathrm{O}\mathrm{O}^{-}\mathrm{N}\mathrm{a}^{+}$$
  • $$\mathrm{C}\mathrm{H}_{3}(\mathrm{C}\mathrm{H}_{2})_{11}\mathrm{N}^{+}(\mathrm{C}\mathrm{H}_{3})_{3}\mathrm{B}\mathrm{r}^{-}$$
A catalyst:
(i) increases the average kinetic energy of reacting molecules
(ii) decrease the activation energy
(iii) alters the reaction mechanism
(iv) increases the frequency of collisions of reacting species.
The true statements are:
  • i, ii, iii
  • all are correct
  • ii, iv
  • ii, iii
During the course of the reaction:
  • catalyst undergoes changes in oxidation state
  • catalyst increases the rate constant
  • catalyst is regenerated in its orginal form when the reactants form the products
  • all are correct
 Choose the correct reason(s) for the stability of the lyophobic colloidal particles.
  • Preferential adsorption of ions on their surface from the solution
  • Preferential adsorption of solvent on their surface from the solution
  • Attraction between different particles having opposite charges on their surface
  • Potential difference between the fixed layer and the diffused layer of opposite charges around the colloidal particles
For a given reaction, energy of activation for forward reaction $$(E_{af})$$ is $$80kJ.mol^{-1}.$$ $$\Delta H = -40kJ.mol^{-1}$$ for the reaction. A catalyst lowers $$E_{af}$$ to $$20 kJ.mol^{-1}.$$ The ratio of energy of activation for reverse reaction before and after addition of catalyst is :
  • 1.0
  • 0.5
  • 1.2
  • 2.0
0:0:1


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