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.

For altering the velocity of a reaction

Only for increasing the velocity of a reaction

Only for decreasing the velocity of a reaction

All (a), (b), and (c) are correct

Increases the average kinetic energy of the reacting molecules.

Increases the frequency of the collisions of the reacting species

MCQ Questions for Class 12 Engineering Chemistry Surface Chemistry Quiz 5

Peptization is a characteristic property of sols.

0%
True
0%
False

The cleansing action of soaps happens with the formation of micelles above the Critical Micelle Concentration. This occurs at:

0%
Above Critical Micelle Temperature
0%
Below Critical Micelle Temperature
0%
Equal Critical Micelle Temperature
0%
None of the above

Select the correct statement(s).

0%
The order of a reaction may be changed with change in the experimental conditions.
0%
The rate of reaction, either exothermic or endothermic, both decreases with decrease in the temperature.
0%
A reaction mixture thermodynamically stable should be kinetically unstable.
0%
A negative catalyst increases the energy of activation.

Which of the following is/are the characteristic(s) of a catalyst?

0%
It changes equilibrium point.
0%
It alter the rate of reaction.
0%
it initiates the reaction.
0%
It increases the average kinetic energy of molecules.

Which of the following statements is/are not correct?

0%
A catalyst always increases the speed of a reaction.
0%
A catalyst does not take part in the reaction.
0%
A catalyst may affect the nature of the products formed.
0%
A catalyst is always an external substance added to the reaction mixture.

Explanation

A catalyst is a substance that may increase or decrease the speed of reaction. It may be added from outside and sometimes may be produced during the reaction. Catalysts are not consumed, they are recycled. Often only tiny amounts are required. A catalyst does not take part in the reaction and it will not take part in the product.

The enzymes in saliva, for example, are catalysts in digestion. I

n chemistry, a substance that causes a chemical reaction to occur but is not itself involved in the reaction.
Hence, options

$B$ and

$D$ are correct options.

Identify the true statement(s) ?

0%
A catalyst is chemically uncharged at the end of a reaction.
0%
A catalyst may appear in the kinetic rate equation of the reaction.
0%
A catalyst will not affect the composition of an equilibrium mixture.
0%
A catalyst cannot cause a non-spontaneous $(\Delta G\, >\, 0)$ reaction to proceed.

Emulsion can be destroyed by:

0%
the addition of emulsifier which tends to form another emulsion
0%
electrophoresis with high potential
0%
freezing
0%
all

Butter is an emulsion of type :

0%
water in oil
0%
oil in water
0%
oil and oil
0%
none of the above

Which is incorrect for a catalyst?

0%
A catalyst can initiate a reaction
0%
A catalyst remains unchanged in quality and composition at the end of reaction
0%
It does not alter the position of equilibrium in a reversible reaction
0%
Catalysts are sometimes very specific in reaction

Which of the following examples is/are oil-in-water-type emulsion?

0%
Ink
0%
Detergent
0%
Soap
0%
Milk

Which one of the following is/are correct statement(s) for physisorption?

0%
It is a reversible process
0%
It requires less heat of adsorption
0%
It requires activation energy
0%
It takes place at low temperature

An emulsifier is an agent which :

0%
accelerates the dispersion
0%
homogenises an emulsion
0%
stabilizes an emulsion
0%
aids the flocculation of an emulsion

Explanation

Hint: An emulsifier is a substance that stabilises the emulsion by increasing its kinetic stability.

Correct Answer:

$C$

Explanation for correct option :

First, let us understand what colloids are:

Colloids are formed by the mixing of the dispersion medium and the dispersed phase which are neither true solutions nor suspensions. The dispersed medium in a colloidal system refers to the medium in which colloidal particles are dispersed while the dispersed phase is the phase dispersed through the medium. Together, dispersed phase and dispersion medium form colloidal systems or colloids.

Coming to the term ‘emulsion’, we see that:

In order to prepare stable emulsions, it is important to add a third component known as an emulsifier or emulsifying agent in suitable amounts. Several types of emulsifiers are known:

(i) Long-chain compounds with polar groups such as soap, sulphonic acid, sulphates, etc.

(ii) Most of the lyophilic colloids also act as emulsifiers such as glue, gelatin, etc.

(iii) Certain insoluble powders as clay, lamp black, etc.

(iv) Soluble substances like iodine also act as emulsifiers.

Therefore, for the purpose of stabilizing the emulsion, an emulsifying agent or an emulsifier is added to the emulsion. For example, milk is an emulsion with liquid fat as the dispersed phase and liquid water as a dispersion medium and casein is the emulsifier.

Hence, option

$(C)$ is the correct option.

Efficiency of the catalyst does not depend on its :

0%
molecular weight
0%
number of free valencies
0%
physical state
0%
amount used

Example of an intrinsic colloid is:

0%
$As_2S_3 sol$
0%
S sol
0%
Egg albumin
0%
$Fe(OH)_2sol$

Explanation

Hint: Lyophilic colloids are also called Intrinsic Colloids.

Correct Answer: Option C

Explanation:

Based on the nature of the interaction between the dispersed phase and the dispersion medium:

Colloids are classified into two categories—lyophilic and lyophobic.

(a) Colloidal solutions in which the dispersed phase has a great affinity or love for the dispersion medium are termed lyophilic colloids. Such substances have a tendency to pass directly into colloidal solution when brought in contact with the dispersion medium. The lyophilic colloids are also called intrinsic colloids. Egg-albumin is an inherent or essential sol.

(b) Lyophobic colloids: Substances which when mixed with the dispersion medium do not form the colloidal sol but their sols can be prepared by special methods.

They are also called extrinsic colloids. Example: Sols of metal sulfides, sols of metallic hydroxides, etc.

Hence, from the above explanation, we can say that the correct answer is option

$C$ .

Soaking of water by a sponge is an example of :

0%
simple adsorption
0%
physical adsorption
0%
chemisorption
0%
absorption

Which of the following statements is/are correct in the case of heterogeneous catalyst?

0%
The catalyst lowers the energy of activation.
0%
The catalyst actually forms a compound with the reactant.
0%
The surface of the catalyst plays a very important role.
0%
There is no change in the energy of activation.

Which one of the followings is/are an example of homogeneous catalysis?

0%
Formation of $SO_3$ in the chamber process.
0%
Formation of $SO_3$ in the contact process.
0%
Hydrolysis of an ester in the presence of acid.
0%
Decomposition of $KClO_3$ in the presence of $MnO_2$ .

Explanation

Catalysts can be divided into two main types: heterogeneous and homogeneous catalysis.

In a heterogeneous reaction, the catalyst is in a different phase from the reactants.

In a homogeneous reaction, the catalyst is in the same phase as the reactants.
Formation of

$SO_3$ in the contact process is heterogeneous catalysis where the reactants and catalyst are in different phase (platinum catalyst).
Remaining all are homogenous catalysis.

A freshly formed precipitate of

$SnO_2$ is peptized by a small amount of NaOH. These colloidal particles may be represented as :

0%
$[SnO_2]SnO_3^{2-}; 2Na^{\oplus}$
0%
$[SnO_2]Sn^{4+}; O^{2-}$
0%
$[SnO_2]Na^{\oplus}; OH^{\ominus}$
0%
$[SnO_2]Sn^{4+}; OH^{\oplus}$

Explanation

A freshly formed precipitate of

$SnO_2$ is peptized by a small amount of NaOH. These colloidal particles may be represented as :

$[SnO_2]SnO_3^{2-}; 2Na^{\oplus}$

$SnO_2$ adsorbes negatively charged

$SnO_3^{2-}$ ions and is surrounded by

$Na^+$ ions which maintains electrical neutrality.

Hence,option A is correct.

Adsorption is the phenomenon in which substance :

0%
accumulates on the surface of the other substance
0%
goes into the body of the other substance
0%
remains close to the other substance
0%
none is the above

Explanation

Hint: Adsorption is the phenomenon in which a substance accumulates on the surface of another substance.

Correct Answer:

$A$

Explanation for correct option :

Adsorption is a process that involves the accumulation of a substance in molecular species in higher concentrations on the surface.

Types of Adsorption

On the basis of interaction forces between adsorbate and adsorbent, adsorption is of two types.

1. Physical adsorption:

This type of adsorption is also known as physisorption. It is due to weak Van der Waals forces between adsorbate and adsorbent.

For example,

$\mathrm{H}_{2}$ and

$\mathrm{N}_{2}$ gases adsorb on coconut charcoal.

2. Chemical adsorption:

This type of adsorption is also known as chemisorption. It is due to strong chemical forces of bonding type between adsorbate and adsorbent. We can take the example involving the formation of iron nitride on the surface when the iron is heated in

$\mathrm{N}_{2}$ gas at

$623 \mathrm{~K}$ .

Conclusion:

It is the phenomenon in which a substance accumulates on the surface of another substance. Thus, it is a surface phenomenon.

So the correct answer is option $$A$$.

In adsorption, the substance which accumulates on the surface of the other substance is termed as:

0%
adsorbate
0%
adsorbent
0%
accumulator
0%
none

A catalyst promoter ___________ the efficiency of a catalyst while a poison ________ the efficiency of the catalyst.

0%
decreases, increases
0%
decreases, decreases
0%
increases, increases
0%
increases, decreases

Explanation

A catalyst promoter increases the efficiency of a catalyst while a poison decreases the efficiency of the catalyst.

Substances which themselves are not catalysts but when mixed in small quantities with the catalysts increase their efficiency are called as promoters or activators. For example, in the Haber process for the synthesis of ammonia, traces of molybdenum increase the activity of finely divided iron which acts as a catalyst.

Substances that destroy the activity of the catalyst by their presence are known as catalytic poisons. For example, the platinum catalyst used in the oxidation of hydrogen is poisoned by

$CO$ .

In the adsorption of oxalic acid on activated charcoal, the activated charcoal is called :

0%
adsorbent
0%
adsorbate
0%
adsorber
0%
absorber

Physical adsorption is appreciable at ............. temperature.

0%
low
0%
high
0%
very high
0%
moderate

Adsorption is a process in which a substance accumulates on the ............. of the other substance.

0%
surface
0%
core
0%
membrane
0%
plasma

True statement is:

0%
Positive catalyst increases the rate of reaction
0%
During the course of the reaction, specific reaction rate remains constant.
0%
Rate constant always increases with rise in temperature whether the reaction is endothermic or exothermic.
0%
All are correct.

Promoters are substances which increase the efficiency of catalyst.

0%
True
0%
False

Acetic acid formed during hydrolysis of ester acts as an induced catalyst.

0%
True
0%
False

Explanation

The given statement is false.
Acetic acid formed during hydrolysis of ester does not act as an induced catalyst. The actual catalyst involved in the mechanism is the hydronium ion

$\displaystyle H_3O^+$ .

TEL, tetraethyl lead, acts as an anti-knocking agent. It acts as:

0%
negative catalyst
0%
catalyst
0%
electophile
0%
nucleophile

Milk is an emulsion of water in oil type.

0%
True
0%
False

Explanation

Oil in water (

$o/w$ ) type: In these emulsions, oil forms the dispersed phase and water in the dispersion medium. For example, milk, vanishing cream, etc. These are also called aqueous emulsions.
Water in oil (

$w/o$ ) type: In these emulsions, water is in the dispersed phase and oil in the dispersion medium. For example, butter, cold cream etc. These are also called oil emulsions.

Gelatin has the minimum protective powers.

0%
True
0%
False
0%
Ambiguous
0%
Data insufficient

Negative catalyst stops the reaction.

0%
True
0%
False

In physical adsorption, the molecules of adsorbate are held by chemical forces.

0%
True
0%
False

The combination of

$N_2$ and

$H_2$ in the presence of

$Fe$ as a catalyst is an example of heterogeneous catalysts.

0%
True
0%
False

Explanation

A Catalyst is a substance which acclerates the rate of a chemical reaction without undergoing any change in its chemical composition or massduring the reaction. A catalyst acclerates the rate of a reaction by lowering the activation energy.

Heterogeneous catalysis refers to the form of catalysis where the phase of the catalyst differs from that of the reactants. Phase here refers not only to solid, liquid or gas but also immiscible liquids. For example, oil and water.
So, combination of

$N_2$ and

$H_2$ in the presence of

$Fe$ as a catalyst is an example of heterogeneous catalysts as

$Fe$ is solid while reactants are gases.

Mark the correct statement in a reversible reaction:

0%
A catalyst catalyzes the forward reaction.
0%
A catalyst catalyzes the backward reaction.
0%
A catalyst influences a direct and reverse reaction to the same extent.
0%
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_____________.

0%
To form a strong enzyme-substrate complex
0%
To decrease the bond energy of all substrate molecules
0%
To change the shape of the substrate molecule
0%
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:

0%
Decreasing in the concentration of oxygen
0%
Powdering the lumps of coal
0%
Decreasing the temperature of coal
0%
Providing inert atmosphere

A catalyst is used:

0%
Only for increasing the velocity of a reaction
0%
For altering the velocity of a reaction
0%
Only for decreasing the velocity of a reaction
0%
All (a), (b), and (c) are correct

An example of autocatalytic reaction is:

0%
Decomposition of nitroglycerine
0%
Thermal decomposition of $KClO_3\, and\, MnO_2$ mixture
0%
Breakdown of $^{14}C_6$
0%
Hydrogenation of vegetable oil using nickel catalysts

Explanation

A chemical reaction is called autocatalytic if at least one of the reaction products acts as a catalyst in the same or in one of the coupled reactions.

$N_2$ is one of the products of decomposition of nitroglycerine plays the role of an autocatalyst.

Which of the following explains the increase of the reaction rate by catalyst ?

0%
Catalyst decreases the rate of backward reaction so that the rate of forward reaction increases.
0%
Catalyst provides extra energy to reacting molecules so that they may produce effective collisions.
0%
Catalyst provides an alternative path o lower activation energy to the reactants.
0%
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:

0%
$MnO_2$ decomposes to give $O_2$
0%
$MnO_2$ provides heat by reacting
0%
better contact is provided by $MnO_2$
0%
$MnO_2$ acts as a catalyst

Explanation

The decomposition of

$KClO_3$ in presence of

$MnO_2$ can be given as follow:

$2KClO_3 \xrightarrow{MnO_2} 2KCl + 3O_2$

In this reaction, the

$MnO_2$ acts as a catalyst. Thus, it increases the rate of the reaction.

Hence, option D is correct.

Which of the following statements regarding catalyst is not true?

0%
A catalyst remains uncharged in composition and quantity at the end of the reaction.
0%
A catalyst can initiate a reaction.
0%
A catalyst does not alter the equilibrium in a reversible reaction.
0%
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?

0%
$SO_4^{2-}$
0%
$MnO_4^{2-}$
0%
$Mn^{2+}$
0%
$K^{\oplus}$

Explanation

In the permanganate titration of oxalic acid in the presence of bench

$H_2SO_4$ (acid medium), it is found that there is slow discharge of the colour of permanganate solution in the beginning but after sometime, the discharge of the colour becomes faster. This is due to the formation of

$MnSO_4$ during the reaction which acts as a catalyst for the same reaction. Thus,

$Mn^{+2}$ is an "auto catalyst" for this reaction. This is an example of auto catalyst.

Milk is an example of water in oil emulsions.

0%
True
0%
False
0%
Ambiguous
0%
Data insufficient

The substance added to increase the stability of a lyophobic sol are called:

0%
promoters
0%
stabilizers
0%
inhibitors
0%
poison

An emulsifier is a substance :

0%
which stabilises an emulsion
0%
which breaks the emulsion into its constituent liquids
0%
which can convert liquid into an emulsion
0%
which bring about coagulation of an emulsion

Explanation

Explanation:

An emulsifier is a substance that acts as a stabilizer in an emulsion and prevents the mixing of two solutions.
An emulsifier has a water-loving hydrophilic head and an oil-loving hydrophobic tail.
The hydrophilic head is for the aqueous phase and the hydrophobic tail is for the oil phase.

e.g. lecithin.

Hence, the correct answer is option $A$ .

A catalyst:

0%
Increases the average kinetic energy of the reacting molecules.
0%
Decreases the activation energy
0%
Alters the reaction mechanism
0%
Increases the frequency of the collisions of the reacting species

Explanation

A positive catalyst decreases the activation energy of a reaction so that the number of molecules are able to cross the activation energy barrier and so the rate of the reaction is increased.

A negative catalyst increases the activation energy of a reaction so that a lesser number of molecules are able to cross the activation energy barrier and so the rate of the reaction is decreased.

A catalyst provides an alternative path for the reaction occurring via a different activation state.

Hence, option $B$ and $C$ are correct

The heat of physisorption lie in the range of :

0%
$1$ to $10$ $kJ\:mol^{-1}$
0%
$20$ to $40$ $kJ\:mol^{-1}$
0%
$40$ to $200$ $kJ\:mol^{-1}$
0%
$200$ to $400$ $kJ\:mol^{-1}$

Explanation

The heat of physisorption lie in the range of 20 to 40

$\displaystyle kJ/mol$ . The value is small as weak van der waals forces are involved. It has negative sign as the adsorption is an exothermic reaction.

Smoke precipitator works on the principle of :

0%
distribution law
0%
neutralization of charge on colloids
0%
Le-Chaterlier's principle
0%
addition of electrolytes

Small liquid droplets dispersed in another liquid is called:

0%
suspension
0%
emulsion
0%
gel
0%
true solution

A catalyst is a substance which:

0%
Increases the equilibrium concentration of the product
0%
Changes the equilibrium constant of the reaction
0%
Shortens the time to reach equilibrium
0%
Supplies energy to the reaction

Dispersed Phase	Dispersion Medium	Name	Example
Solid	Solid	Solid sol	Coloured glass, gems, alloys
Solid	Liquid	sol	Paints, inks, white of eggs mud
Solid	Gas	Aerosol	Smoke, dust
Liquid	Solid	Gel	Curds, pudding, cheese, jellies
Liquid	Liquid	Emulsion	Milk, Cream, Better', Oil in water
Liquid	Gas	Liquid Aerosol	Clouds, Mist, fog (water in air)

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

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Practice Class 12 Engineering Chemistry Quiz Questions and Answers

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

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Practice Class 12 Engineering Chemistry Quiz Questions and Answers

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