CBSE Questions for Class 12 Engineering Chemistry Surface Chemistry Quiz 5 - MCQExams.com

Peptization is a characteristic property of sols.
  • True
  • False
The cleansing action of soaps happens with the formation of micelles above the Critical Micelle Concentration. This occurs at:
  • Above Critical Micelle Temperature
  • Below Critical Micelle Temperature
  • Equal Critical Micelle Temperature
  • None of the above
Select the correct statement(s).
  • The order of a reaction may be changed with change in the experimental conditions.
  • The rate of reaction, either exothermic or endothermic, both decreases with decrease in the temperature.
  • A reaction mixture thermodynamically stable should be kinetically unstable.
  • A negative catalyst increases the energy of activation.
Which of the following is/are the characteristic(s) of a catalyst?
  • It changes equilibrium point.
  • It alter the rate of reaction.
  • it initiates the reaction.
  • It increases the average kinetic energy of molecules.
Which of the following statements is/are not correct?
  • A catalyst always increases the speed of a reaction.
  • A catalyst does not take part in the reaction.
  • A catalyst may affect the nature of the products formed.
  • A catalyst is always an external substance added to the reaction mixture.
Identify the true statement(s) ?
  • A catalyst is chemically uncharged at the end of a reaction.
  • A catalyst may appear in the kinetic rate equation of the reaction.
  • A catalyst will not affect the composition of an equilibrium mixture.
  • A catalyst cannot cause a non-spontaneous $$(\Delta G\, >\, 0)$$ reaction to proceed.
Emulsion can be destroyed by:
  • the addition of emulsifier which tends to form another emulsion
  • electrophoresis with high potential
  • freezing
  • all
Butter is an emulsion of type :
  • water in oil
  • oil in water
  • oil and oil
  • none of the above
Which is incorrect for a catalyst?
  • A catalyst can initiate a reaction
  • A catalyst remains unchanged in quality and composition at the end of reaction
  • It does not alter the position of equilibrium in a reversible reaction
  • Catalysts are sometimes very specific in reaction
Which of the following examples is/are oil-in-water-type emulsion?
  • Ink
  • Detergent
  • Soap
  • Milk
Which one of the following is/are correct statement(s) for physisorption?
  • It is a reversible process
  • It requires less heat of adsorption
  • It requires activation energy
  • It takes place at low temperature
An emulsifier is an agent which :
  • accelerates the dispersion
  • homogenises an emulsion
  • stabilizes an emulsion
  • aids the flocculation of an emulsion
Efficiency of the catalyst does not depend on its :
  • molecular weight
  • number of free valencies
  • physical state
  • amount used
Example of an intrinsic colloid is:
  • $$As_2S_3 sol$$
  • S sol
  • Egg albumin
  • $$Fe(OH)_2sol$$
Soaking of water by a sponge is an example of :
  • simple adsorption
  • physical adsorption
  • chemisorption
  • absorption
Which of the following statements is/are correct in the case of heterogeneous catalyst?
  • The catalyst lowers the energy of 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.
Which one of the followings is/are an example of homogeneous catalysis?
  • Formation of $$SO_3$$ in the chamber process.
  • Formation of $$SO_3$$ in the contact process.
  • Hydrolysis of an ester in the presence of acid.
  • Decomposition of $$KClO_3$$ in the presence of $$MnO_2$$.
A freshly formed precipitate of $$SnO_2$$ is peptized by a small amount of NaOH. These colloidal particles may be represented as :
  • $$[SnO_2]SnO_3^{2-}; 2Na^{\oplus}$$
  • $$[SnO_2]Sn^{4+}; O^{2-}$$
  • $$[SnO_2]Na^{\oplus}; OH^{\ominus}$$
  • $$[SnO_2]Sn^{4+}; OH^{\oplus}$$
Adsorption is the phenomenon in which substance :
  • accumulates on the surface of the other substance
  • goes into the body of the other substance
  • remains close to the other substance
  • none is the above
In adsorption, the substance which accumulates on the surface of the other substance is termed as:
  • adsorbate
  • adsorbent
  • accumulator
  • none
A catalyst promoter ___________ the efficiency of a catalyst while a poison ________ the efficiency of the catalyst.
  • decreases, increases
  • decreases, decreases
  • increases, increases
  • increases, decreases
In the adsorption of oxalic acid on activated charcoal, the activated charcoal is called :
  • adsorbent
  • adsorbate
  • adsorber
  • absorber
Physical adsorption is appreciable at ............. temperature.
  • low
  • high
  • very high
  • moderate
Adsorption is a process in which a substance accumulates on the ............. of the other substance.
  • surface
  • core
  • membrane
  • plasma
True statement is:
  • Positive catalyst increases the rate of reaction
  • During the course of the reaction, specific reaction rate remains constant.
  • Rate constant always increases with rise in temperature whether the reaction is endothermic or exothermic.
  • All are correct.
Promoters are substances which increase the efficiency of catalyst.
  • True
  • False
Acetic acid formed during hydrolysis of ester acts as an induced catalyst.
  • True
  • False
TEL, tetraethyl lead, acts as an anti-knocking agent. It acts as:
  • negative catalyst
  • catalyst
  • electophile
  • nucleophile
Milk is an emulsion of water in oil type.
  • True
  • False
Gelatin has the minimum protective powers.
  • True
  • False
  • Ambiguous
  • Data insufficient
Negative catalyst stops the reaction.
  • True
  • False
In physical adsorption, the molecules of adsorbate are held by chemical forces.
  • True
  • False
The combination of $$N_2$$ and $$H_2$$ in the presence of $$Fe$$ as a catalyst is an example of heterogeneous catalysts.
  • True
  • False
Mark the correct statement in a reversible reaction:
  • A catalyst catalyzes the forward reaction.
  • A catalyst catalyzes the backward reaction.
  • A catalyst influences a direct and reverse reaction to the same extent.
  • A catalyst increases the rate of forward reaction and decreases the rate of backward reaction.
The efficiency of an enzyme in catalyzing a reaction is due to its capacity_____________.
  • To form a strong enzyme-substrate complex
  • To decrease the bond energy of all substrate molecules
  • To change the shape of the substrate molecule
  • To lower the activation energy of the reaction
Burning of coal is represented as $$C(s)\, +\, O_2(g)\, \rightarrow\, CO_2(g).$$ The rate of this reaction is increased by:
  • Decreasing in the concentration of oxygen
  • Powdering the lumps of coal
  • Decreasing the temperature of coal
  • Providing inert atmosphere
A catalyst is used:
  • Only for increasing the velocity of a reaction
  • For altering the velocity of a reaction
  • Only for decreasing the velocity of a reaction
  • All (a), (b), and (c) are correct
An example of autocatalytic reaction is:
  • Decomposition of nitroglycerine
  • Thermal decomposition of $$KClO_3\, and\, MnO_2$$ mixture
  • Breakdown of $$^{14}C_6$$
  • Hydrogenation of vegetable oil using nickel catalysts
Which of the following explains the increase of the reaction rate by catalyst ?
  • Catalyst decreases the rate of backward reaction so that the rate of forward reaction increases.
  • Catalyst provides extra energy to reacting molecules so that they may produce effective collisions.
  • Catalyst provides an alternative path o lower activation energy to the reactants.
  • Catalyst increases the number of collisions between the reacting molecules.
When $$KClO_3$$ is heated, it decomposes into $$KCl$$ and $$O_2$$. If some $$MnO_2$$ is added, the reaction goes much faster because:
  • $$MnO_2$$ decomposes to give $$O_2$$
  • $$MnO_2$$ provides heat by reacting
  • better contact is provided by $$MnO_2$$
  • $$MnO_2$$ acts as a catalyst
Which of the following statements regarding catalyst is not true?
  • A catalyst remains uncharged in composition and quantity at the end of the reaction.
  • A catalyst can initiate a reaction.
  • A catalyst does not alter the equilibrium in a reversible reaction.
  • Catalysts are sometimes very specific in respect of reaction.
The oxidation of oxalic acid by acidified $$KMnO_4$$ is an example of autocatalysis. It is due to which of the following?
  • $$SO_4^{2-}$$
  • $$MnO_4^{2-}$$
  • $$Mn^{2+}$$
  • $$K^{\oplus}$$
Milk is an example of water in oil emulsions.
  • True
  • False
  • Ambiguous
  • Data insufficient
The substance added to increase the stability of a lyophobic sol are called:
  • promoters
  • stabilizers
  • inhibitors
  • poison
An emulsifier is a substance :
  • which stabilises an emulsion
  • which breaks the emulsion into its constituent liquids
  • which can convert liquid into an emulsion
  • which bring about coagulation of an emulsion
A catalyst:
  • Increases the average kinetic energy of the reacting molecules.
  • Decreases the activation energy
  • Alters the reaction mechanism
  • Increases the frequency of the collisions of the reacting species
The heat of physisorption lie in the range of :
  • $$1$$ to $$10$$ $$kJ\:mol^{-1}$$
  • $$20$$ to $$40$$ $$kJ\:mol^{-1}$$
  • $$40$$ to $$200$$ $$kJ\:mol^{-1}$$
  • $$200$$ to $$400$$ $$kJ\:mol^{-1}$$
Smoke precipitator works on the principle of :
  • distribution law
  • neutralization of charge on colloids
  • Le-Chaterlier's principle
  • addition of electrolytes
Small liquid droplets dispersed in another liquid is called:
  • suspension
  • emulsion
  • gel
  • true solution
A catalyst is a substance which:
  • Increases the equilibrium concentration of the product
  • Changes the equilibrium constant of the reaction
  • Shortens the time to reach equilibrium
  • Supplies energy to the reaction
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