$$\mathrm{A}\mathrm{s}_{2}\mathrm{S}_{3}$$ sol

$$\mathrm{F}\mathrm{e}(\mathrm{O}\mathrm{H})_{3}$$ sol

negatively as well as positively charged particles

MCQ Questions for Class 12 Engineering Chemistry Surface Chemistry Quiz 4

Which of the following catalyst is used in contact process for manufacture of

$H_{2}SO_{4}$ ?

0%
Oxides of nitrogen
0%
$V_{2}O_{5}$
0%
$Fe_{2}O_{3}$
0%
Platinised asbestos

Explanation

Vanadium (V) Oxide,

$V_2O_5$ is used as catalyst in this reaction. It increases the rate of the reaction, thus reducing the need for a high temperature.

Gelatin protects

0%
Gold sol
0%
$\mathrm{A}\mathrm{s}_{2}\mathrm{S}_{3}$ sol
0%
$\mathrm{F}\mathrm{e}(\mathrm{O}\mathrm{H})_{3}$ sol
0%
All of these

Explanation

Gelatin is lyophilic sol. Lyophilic sol are formed by the direct mixing of substance in effective dispersing medium. These sols have strong force of interaction between dispersed phase and dispersed medium.
Gold sol, $As_{2}O_{3}$ and $Fe(OH)_{3}$ are lyophobic sols. Lyophobic sols have weaker force of interaction between dispersed phase and dispersed medium.
When a lyophilic sol is added to lyophobic sol, then a protective layer of lyophilic sol formed around each colloidal particle of the lyophobic sol which protects them from coagulation caused by electrolytes. Therefore, Gelatin protects Gold sol, $As_{2}O_{3}$ sol and $Fe(OH)_{3}$ sol.

Hence, the correct answer is option D.

The process of making colloidal solution from a precipitate is called ________.

0%
coagulation
0%
vulcanization
0%
peptization
0%
flocculation

In presence of acetanilide, the rate of decomposition of

$H_{2}O_{2}$ reduced. Acetanilide is called a positive catalyst.

0%
True
0%
False

Which of the following statement is incorrect?

0%
Enzymes are in colloidal state
0%
Enzymes are catalysts
0%
Enzymes can catalyze any reaction
0%
Urease is an enzyme

Finely powered or colloidal catalyst particles having small surface area are rich in free valencies.
State whether the statement is True or False

0%
The statement is True
0%
The statement is False
0%
Neither
0%
Finely powered or colloidal catalyst particles having large surface area are rich in free valencies.

Which of the following statements about a catalyst is/are true?

0%
A catalyst accelerates the reaction by bringing down the energy of activation.
0%
A catalyst does not take part in the reaction.
0%
A catalyst makes the reaction more feasible by making the $\Delta G^{\circ}$ more negative.
0%
A catalyst makes the equilibrium constant of the reaction more favourable for the forward reaction.

Explanation

Hint: A catalyst does not affect the thermodynamic parameters of a reaction such as enthalpy, entropy, Gibbs energy, and equilibrium constant.

Explanation for Correct Answer:

A catalyst increases the rate of the reaction by lowering the activation energy.
The diagram suggests the activation energy with the catalyst and without the catalyst as below;

The effect of catalysts on rates of reaction

As Catalyst increases the reaction rate by lowering the activation energy, So, Option A is correct.
Catalyst does not take part actively in the reaction, it just is consumed in one step and regenerated in another step. and it requires in a very small quantity. So, Option B is also correct.

Explanation for Incorrect Answer:

A catalyst does not affect the thermodynamic parameters of a reaction. So, Option C is Incorrect

A catalyst does not affect the equilibrium constant of a reaction. It just speeds up the rate of attainment of equilibrium. So, Option D is Incorrect.

Final answer: Option $A$ and $B$ .

The magnitude of ______________ decreases in the presence of a catalyst.

0%
activation energy
0%
dissociation energy
0%
energy barrier
0%
intermolecular forces

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

0%
Haber's process of synthesis of ammonia
0%
Catalytic conversion of $SO_{2}$ to $SO_{3}$ in Contact process
0%
Catalytic hydrogenation of oils
0%
Acid hydrolysis of methyl acetate

Explanation

Hint: Homogenous catalysts are those in which the catalyst is in the same phase as the reactants and products.

Explanation:

A) Haber's process: It combines nitrogen from the air with hydrogen derived mainly from natural gas (methane) into ammonia using Iron oxide catalyst at higher temperature and pressure. The reaction is shown as;

$N_{2(g)} +3H_{2(g)} \xrightarrow{FeO_{(s)}} 2NH_{3(g)}$

Here, Catalyst is in Solid-phase while reactants are in gases phases. So, it is an example of heterogeneous catalysis.

B) Contact process: It involves the following steps:
1. makes sulfur dioxide by burning sulfur in excess of air/oxygen.
2. converts the sulfur dioxide into sulfur trioxide in the presence of a catalyst vanadium pentoxide ($$

V_2O_5$$V2O5)
Reaction is shown as;

$SO_{2(g)} + 0.5O_{2(g)} \xrightarrow{V_2O_{5(s)}} SO_{3(g)}$

Here, Catalyst is in Solid-phase while reactants are in gases phases. So, it is an example of heterogeneous catalysis.

C) Catalytic hydrogenation is the addition of hydrogen to an unsaturated compound with a double or triple bond such as oil. The process of catalytic hydrogenation utilizes a metal catalyst such as nickel, palladium, or platinum. the reaction is shown as;

$Unsaturated_{(l)} +H_{2(g)} \xrightarrow{Ni_{(s)}} Saturated_{(l)}$

Here, Catalyst is in Solid-phase while reactants are in gases phases. So, it is an example of heterogeneous catalysis.

D) Acid hydrolysis of methyl acetate is catalyzed by dilute acid, where it gets converted to methanol and acetic acid. The reaction is shown as;

$MeOCOCH_{3(aq.)} + H_2O_{(l)} \xrightarrow{H^+_{(aq)}} MeOH_{(aq.)} + AcOH_{(aq.)}$

Here catalyst and the reactants both are in the liquid (Aqueous) phase so it is an example of Homogenous catalysis.

Final answer: Correct Option is $D$

In a reversible reaction, a catalyst :

0%
increases the rate of the forward reaction only
0%
increases the rate of forward reaction to a greater extent then that of the backward reaction
0%
increases the rate of the forward reaction and decreases that of the backward reaction to different extent
0%
increases the rate of the forward and backward reaction equally

Catalytic poisoning is due to:

0%
increasing activation energy
0%
adsorption of poisoner on the reactants surface
0%
adsorption of poisoners on the catalyst surface
0%
increase in heat of reaction

Which is not correct for an oil-water emulsion?

0%
It imparts dye colour with water soluble dye.
0%
It can be diluted with water.
0%
It has higher viscosity in comparison to water-oil emulsion.
0%
It consists of vanishing cream.

Which one of the following characteristics is not correct for physical adsorption?

0%
Adsorption is spontaneous
0%
Both enthalpy and entropy of adsorption
0%
Adsorption on solid is reversible
0%
Adsorption increases with increase in temperature

Explanation

Physical adsorption decreases with an increase in temperature because an increase in temperature leads to an increase in kinetic energy of molecules and hence, their desorption. Since physical adsorption is an exothermic process, it occurs more readily at lower temperatures and decreases with an increase in temperature (Le-Chatelier's Principle). If the adsorption is a spontaneous phenomenon, it should be exothermic, at least for adsorption from the gaseous phase.

A molecule in the gas phase will have an entropy higher than in the adsorbed state, then the

$\Delta S$ should be negative, the only way to have a

$\Delta G$ negative (spontaneous) is to have a

$\Delta H$ negative (exothermic process). Therefore, the process will be spontaneous

$(\Delta G = -ve)$ if the temperature is low.

Which reactions represents heterogeneous catalysis?

0%
Decomposition of KClO $_3$ in presence of MnO $_2$
0%
Ostwald process for HNO $_3$
0%
Contact process for H $_2$ SO $_4$
0%
Acidic hydrolysis of ester

Explanation

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.
All other given reactions are example of this but in acidic hydrolysis, reactant and catalyst (

$H^+$ ) both are miscible liquids. So, it is homogeneous catalysis.

Bredig's arc method involves :

0%
dispersion
0%
condensation
0%
peptization
0%
dispersion and condensation both

A catalyst is a substance that :

0%
helps in attaining equilibrium faster (if any)
0%
increases the rate of forward and backward reaction (if any)
0%
lowers the threshold energy level
0%
provides new pathway to reaction

About positive and negative catalyst, which of the following statements is incorrect?

0%
Positive catalyst lowers the energy of activation
0%
Negative catalyst decreases the energy of activation
0%
Positive catalyst increases the rate of reaction
0%
Negative catalyst functions to remove active intermediates

$CO + H_2{\rightarrow } CH_3 OH$

Which catalyst is used in the above reaction?

0%
$MnO_2$
0%
$FeCl_3$
0%
$PdCl_2$
0%
$ZnO/CuO$

Explanation

$2H_2 + CO \rightarrow CH_3OH$ with ZnO/CuO as a catalyst.

and

Ni catalyst is used in a process called steam reforming where methane is mixed with steam at high temperature to create hydrogen gas and carbon monoxide.

Which of the following is not an example of a heterogeneous 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 $H^+$ ions.
0%
Combination of $H_2$ and $Cl_2$ in the presence of moisture.

Explanation

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 vs gas but also immiscible liquids.
In acidic hydrolysis, reactants and catalyst (

$H^+$ ), both are miscible liquids and therefore, is homogeneous catalysis.
Combination of

$H_2$ and

$Cl_2$ in the presence of moisture, here reactant and catalyst both are gaseous.
Formation of

$SO_3$ in the contact process, here air is used as catalyst.
In this method, sulphur dioxide made by either burning sulphur in excess of air or by roasting of sulphide ores.

Mark the incorrect statement.
A catalyst :

0%
remains chemically unchanged at the end of a chemical reaction
0%
is used up in the course of a reaction
0%
is a reactant required in small quantity
0%
is not specific

What type of bond would exist between this soap and oil?

0%
Hydrogen bonds
0%
Dispersion forces
0%
Covalent bonds
0%
Dipole-dipole forces

Which type of metals form effective catalysts?

0%
Alkali metals
0%
Transition metals
0%
Alkaline earth metals
0%
Radioactive metals

When oil and water are into the same vessel, two layers are observed with the less dense oil on top. These two liquids are said to be:

0%
hydrophilic
0%
hydrophobic
0%
insoluble
0%
immiscible

Which gas will be adsorbed on a solid to greater extent?

0%
A gas having non polar molecule.
0%
A gas having highest critical temperature $\displaystyle \left ( T_{c} \right )$ .
0%
A gas having lowest critical temperature.
0%
A gas having highest critical pressure.

Cod liver oil is:

0%
fat dispersed in water
0%
water dispersed in fat
0%
water dispersed in oil
0%
fat dispersed in fat

Adsorption is multilayer in case of:

0%
physical adsorption
0%
chemisorption
0%
in both
0%
none of the these

Blood contains:

0%
positively charged particles
0%
negatively charged particles
0%
neutral particles
0%
negatively as well as positively charged particles

Catalytic poisoners act by:

0%
coagulating the catalyst
0%
getting adsorbed on the active centres on the surface of catalyst
0%
chemical combination with any one of the reactants
0%
none of the above

Select the correct statement(s).

0%
When $T\longrightarrow \infty$ or ${{E}_{a}}\longrightarrow 0$ , then $k=A$ .
0%
A positive catalyst can change $\Delta H$ of the reaction.
0%
A mixture of reactants may be thermodynamically unstable but kinetically stable.
0%
A negative catalyst increases the activation energy of the reaction.

Explanation

A) As

$k=Ae^{(-E_a/RT)}$ , so it will be equal to A when

$T\longrightarrow \infty$ or

${{E}_{a}}\longrightarrow 0$ .
B) Catalyst never changes the overall energy of a reaction.
C) A reaction can be thermodynamically unstable but kinetically stable because the conditions are such that the rate of the reaction is zero. A mixture of coal and oxygen are kinetically stable because the condition for combustion are not obtained until the coal is heated to its ignition temperature. The system is thermodynamically unstable because at equilibrium the coal oxygen reaction favors the formation of

$CO_2$ .
D) A negative catalyst increases the activation energy of the reaction and slows down the rate of reaction.

Reversible adsorption is:

0%
chemical adsorption
0%
physical adsorption
0%
both
0%
none

An emulsion is a colloidal system of ____________:

0%
two solids
0%
two liquids
0%
one gas and one solid
0%
one gas and one liquid

Cleansing action of soap occurs because:

0%
oil and grease can be absorbed into the hydrophobic centres of soap micelles and washed away
0%
oil and grease can be absorbed into hydrophilic centres of soap micelles and washed away
0%
oil and grease can be absorbed into both hydrophilic and hydrophobic centres but cannot be washed away
0%
cleansing action is not related to micelles

The catalyst used in making

$H_2SO_4$ in contact process is :

0%
$V_2O_5$
0%
$Fe_2O_3$
0%
$Cr_2O_3$
0%
$CrO_3$

Explanation

The contact process is the current method of producing sulfuric acid in the high concentrations needed for industrial processes. Platinum used to be the catalyst for this reaction. However, as it is susceptible to reacting with arsenic impurities in the sulfur feedstock, vanadium(V) oxide

$(V_2O_5)$ is now preferred.

Which of the following element is responsible for oxidation of water to

$O_2$ is biological processes?

0%
Fe
0%
Cu
0%
Mn
0%
Mo

Mention catalyst in the following reaction:

$C_2H_4 {\rightarrow } CH_3 CHO$

0%
$MnO_2$
0%
$FeCl_3$
0%
$PdCl_2$
0%
$ZnO/CuO$

Explanation

The catalyst used for the conversion

$C_2H_4 {\rightarrow } CH_3 CHO$ is

$PdCl_2$ .

The given reaction is called Wacker's process. It is used to prepare aldehyde by hydrolysis of alkene in the presence of

$PdCl_2$ . The reaction can be given as follow:

$H_2C=CH_2 + PdCl_2 + H_2O \rightarrow CH_3CHO + 2HCl + Pd^{2+}$

For the above reaction, the catalyst is a two-component system consisting of

$PdCl_2$ and

$CuCl_2$ .

Option (C) is correct.

Adsorption is a surface phenomenon.

0%
True
0%
False

Which is not correct in case of catalyst?

0%
A catalyst is active only in solution.
0%
The addition of catalyst changes the equilibrium constant.
0%
A catalyst speeds up forward reaction and slows the backward reaction.
0%
The composition of equilibrium mixtures is not changed by a catalyst.

Which statements is true in case of catalyst?

0%
The catalyst is unchanged chemically at the end of a reaction.
0%
The catalyst accelerated the reaction.
0%
In a reversible reaction, the catalyst alters the equilibrium position.
0%
A small amount of catalyst is often sufficient to bring about a large change in reaction.

Thermal decomposition of

$KClO_3(s)$ in presence of

$MnO_2(s)$ is homogeneous catalysis.

0%
True
0%
False

Explanation

Thermal decomposition of

$KClO_3(s)$ in presence of

$MnO_2(s)$ is heterogeneous catalysis as gaseous product is form along with solid

$KCl$ .

$2KCl{ O }_{3(s)}\xrightarrow { Mn{ O }_{ 2 } } 2KCl_{(s)}+3{ O }_{ 2(g) }$

Combination of

$N_2$ and

$H_2$ in presence of

$Fe$ as catalyst is an example of homogeneous catalysis.

0%
True
0%
False

Explanation

Combination of

$N_2$ and

$H_2$ in presence of

$Fe$ as catalyst is an example of heterogeneous catalysis. Nitrogen and hydrogen are in gaseous form while iron is in solid powdered form.

Which is true in case of catalyst?

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

Decomposition of

$H_2O_2$ is prevented in presence of :

0%
acetanilide
0%
glycol
0%
oxygen
0%
none of the above

Explanation

Decomposition of

$H_2O_2$ is prevented in the presence of acetanilide. Acetanilide acts as a stabilizer which when added to the solutions retards the decomposition.

On adding few drops of dilute

$HCl$ or

$FeCl_3$ to freshly precipitated ferric hydroxide, a red coloured colloidal solution is obtained. This phenomenon is known as :

0%
peptization
0%
dialysis
0%
protection
0%
dissolution

Peptization is a process of :

0%
precipitating colloidal particles.
0%
purifying colloidal particles.
0%
dispersing the precipitate into colloidal state.
0%
none of the above.

Tanning of leather is the :

0%
colouring of leather by chemicals
0%
drying process to make the leather hard
0%
polishing of leather to make it look attractive
0%
coagulative hardening of the leather by chemicals

Gelatin is often used as an ingredient in the manufacture of ice-cream. The reason for this is :

0%
to prevent the formation of a colloid.
0%
to stabilize the colloid and prevent crystal growth.
0%
to cause the mixture to solidify.
0%
to improve the flavour.

The rate of decomposition of aldehyde

$(CH_3CHO)$ into

$CH_4$ and

$CO$ in presence of

$I_2$ at 800 K follows the rate law:

$r=K[CH_3CHO][I_2]$ . The decomposition is believed to go to the two step mechanism:

$CH_3CHO+I_2\rightarrow CH_3I+HI+CO$

$CH_3I+HI\rightarrow CH_4+I_2$

What is the catalyst for the reaction? Which of the two steps is the slower one?

0%
$HI, I^{st} \ step$
0%
$I_2, I^{st} \ step$
0%
$HI, II^{st}\ step$
0%
$I_2, II^{st}\ step$

Which of the following are governed by emulsion formation?

0%
Preparation of food stuffs.
0%
Food digestion in intestine.
0%
Preparation of many cosmetic products.
0%
Process of cementation.

The colloidal system in which the disperse phase and dispersion medium are both liquids is known as:

0%
an emulsion
0%
an aerosol
0%
a gel
0%
a foam

Rate of reaction (r) is plotted against temperature (T) for an enzyme catalysed reaction. Which of the following is correct representation?

Explanation

Option (B) is correct.

Enzyme catalysed reactions have optimium temperature range

$35^oC$ . As the temperature increases, the speed of movement of substrate and enzymes molecules also continues to increase. But above certain temperature (

$35^oC$ ) called as optimum temperature, enzymes gets denatured.

CBSE Questions for Class 12 Engineering Chemistry Surface Chemistry Quiz 4 - 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 4 - MCQExams.com

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Practice Class 12 Engineering Chemistry Quiz Questions and Answers

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