Chemical Kinetics Test

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Chemical Kinetics Test - 4

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Question 1
1 / -0

Assertion: For each ten degree rise of temperature, the specific constant rate is nearly doubled.
Reason: Energy-wise distribution of molecules in a gas is an exponential function of temperature.

A
Both A and R are true and R is the correct explanation of A.

B
Both A and R are true but R is not the correct explanation of A.

C
A is true but R is false.

D
A is false but R is true.

E
Both A and R are false.

Solution

This option is correct because energy-wise distribution of molecules in a gas is an exponential function of temperature, is the correct explanation of assertion.
Question 2
1 / -0

Directions: For the assertion (A) and reason (R) below, choose the correct alternative

Assertion: The rate of reaction is accelerated by the presence of catalyst.
Reason: The presence of catalyst makes the value of ∆G˚ more negative.

A
Both A and R are true and R is the correct explanation of A.

B
Both A and R are true, but R is not the correct explanation of A.

C
A is true, but R is false.

D
A is false, but R is true.

E
Both A and R are false.

Solution

The reason is false. The correct reason is: presence of catalyst lowers the activation energy barrier and increases the rate of reaction.
Question 3
1 / -0

Assertion: The reaction 2NO + O₂ → 2NO₂ and CO₂ + O₂ → 2CO₂ proceed at the same rate because they are similar.
Reason: Both the reactions have the same activation energy.

A
Both A and R are true and R is the correct explanation of A.

B
Both A and R are true but R is not the correct explanation of A.

C
A is true but R is false.

D
A is false but R is true.

E
Both A and R are false.

Solution

The assertion and reason both are false because the given reactions proceed at different rates and the given reactions have different activation energies. Thus, this option is correct.
Question 4
1 / -0

Assertion: In rate laws, unlike the expression for equilibrium constants, the exponents for concentrations do not necessarily match the stoichiometric coefficients.
Reason: It is the mechanism and not the balance chemical equation for the overall change that governs the reaction rate.

A
Both A and R are true and R is the correct explanation of A.

B
Both A and R are true but R is not the correct explanation of A.

C
A is true but R is false.

D
A is false but R is true.

E
Both A and R are false.

Solution

This option is correct because assertion and reason both are true and reason is the correct explanation of assertion that the overall rate of reaction depends upon the slow step.
Question 5
1 / -0

Assertion: The molecularity of reaction: H₂ + Br₂ → HBr is 2.
Reason: The order of this reaction is .

A
Both A and R are true and R is the correct explanation of A.

B
Both A and R are true but R is not the correct explanation of A.

C
A is true but R is false.

D
A is false but R is true.

E
Both A and R are false.

Solution

This option is correct because the explanation is not correct, so the correct explanation is, order does not depend upon the molecularity or vice versa.
Question 6
1 / -0

Assertion: The addition of catalyst lowers the activation barrier, yet there is no change in the enthalpy.
Reason: Enthalpy image is equal to the difference in the activation energies for the forward and the backward reactions.

A
Both A and R are true and R is the correct explanation of A.

B
Both A and R are true but R is not the correct explanation of A.

C
A is true but R is false.

D
A is false but R is true.

E
Both A and R are false.

Solution

This option is correct because enthalpy image is equal to the difference in the activation energies for the forward and the backward reactions, is correct explanation of assertion.
Question 7
1 / -0

Assertion: A photochemical reaction that can take place in presence of red light can also take place in presence of violet light but the reverse is not true.
Reason: Red light has lower wave length than violet light.

A
Both A and R are true and R is the correct explanation of A.

B
Both A and R are true but R is not the correct explanation of A.

C
A is true but R is false.

D
A is false but R is true.

E
Both A and R are false.

Solution

This option is correct because the red light has lower frequency or energy than violet light.
Question 8
1 / -0

Assertion: The photochemical reactions H₂ + Cl₂ → 2HCl and H₂ + Br₂ → 2HBr have equal quantum efficiencies.
Reason: Both the reactions proceed by similar mechanism.

A
Both A and R are true and R is the correct explanation of A.

B
Both A and R are true but R is not the correct explanation of A.

C
A is true but R is false.

D
A is false but R is true.

E
Both A and R are false.

Solution

This option is correct because H₂ + Cl₂ → 2HCl has mush higher quantum efficiency than H₂ + Br₂ → 2HBr and the first step of secondary process of H₂ + Cl₂ → 2HCl is exothermic while the same for H₂ + Br₂ → 2HBr is endothermic.
Question 9
1 / -0

Which of the following statements is/are wrong?
A. The rate of a reaction remains constant throughout the reaction.
B. The higher the activation energy of a reaction, the slower is the rate of the reaction.
C. For the reaction N₂ + 3H₂ → 2NH₃, the rate of reaction is same when expressed in terms of N₂, H₂ and NH₃.

A
Only A

B
Only B

C
Only C

D
None of these

E
All of these

Solution

This option is correct because the rate of reaction decreases with time because concentration of reactants decreases with time.
Question 10
1 / -0

Select the correct statement(s).
A. The order of reaction is never negative with respect to any reactant or product.
B. Rate of reaction and rate constant of a second order reaction have the same unit.
C. Order of a reaction can be fractional but molecularity is never fractional.

A
Only A

B
Only B

C
Only C

D
A and B

E
B and C

Solution

This option is correct because the rate of reaction and rate constant of a second order reaction have the same unit and order of a reaction can be fractional but molecularity is never fractional, are the correct statements.
Question 11
1 / -0

Choose the false statement(s)
A. The free energy change of a photochemical reaction is always negative for the reaction to be spontaneous.
B. For 10˚ rise the temperature, the rate of reaction is almost doubled because the number of collisions is almost double.
C. Order of the reaction is independent of the change in conditions such as temperature, pressure etc.

A
Only A

B
Only B

C
Only C

D
All of these

E
None of these

Solution

This option is correct because the free energy change of a photochemical reaction may not be negative in certain cases, for 10˚ rise the temperature, the rate of reaction is almost doubled because the number of effective collisions is almost doubled and order of the reaction can change with change in conditions such as temperature, pressure etc.
Question 12
1 / -0

Which of the following statements is/are correct for reactions of first order?
A. Rate law is more informative than law of mass action for the development of mechanism.
B. For the reaction 2O₃ → 3O₂ order with respect to O₂ is negative.
C. The presence of catalyst lowers the activation energy barrier.

A
Only A

B
Only B

C
Only C

D
None of these

E
All of these

Solution

This option is correct because rate law is more informative than law of mass action for the development of mechanism, in the reaction 2O₃ → 3O₂ order with respect to O₂ is -1 and the catalyst lowers the activation energy barrier, all are true statements.
Question 13
1 / -0

Which of the following statements is/are incorrect?
A. Rate law expression cannot be written from the stoichiometric equation.
B. Law of mass action expression can be written from the balance equation.
C. Rate of reaction and rate of constant have same units.

A
Only A

B
Only B

C
Only C

D
None of these

E
All of these

Solution

This option is correct because the units of rate constant depend upon the order of reaction.
Question 14
1 / -0

If the reaction rate at a given temperature becomes slow, then which of the following is/are true?
A. The free energy of activation is higher.
B. The free energy of activation is lower.
C. The initial concentration of the reactants remains the constant.

A
Only A

B
Only B

C
Only C

D
B and C

E
A and B

Solution

This option is correct because slower reaction rate indicates higher free energy of activation.
Question 15
1 / -0

Consider the following statements:
The rate law for the acid catalysed hydrolysis of an ester being given as:
Rate = k[H⁺][ester] = k'[ester]
If the acid concentration is doubled at constant ester concentration,
A. the second order rate constant, k is doubled
B. the pseudo first order rate constant, k is doubled
C. the rate of the reaction is doubled

Which of the above statements are correct?

A
A and B

B
B and C

C
A and C

D
All of these

E
None of these

Solution

This option is correct because pseudo first order rate constant as well as rate of reaction are doubled. It may be noted that in presence of acid, hydrolysis of ethyl acetate is a pseudo-unimolecular reaction but the actual value of k depends upon the concentration of H⁺ ions, otherwise rate constant of a reaction is constant at constant temperature.

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Chemical Kinetics Test - 4

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Chemical Kinetics Test - 4

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Question 1

Both A and R are true and R is the correct explanation of A.

Both A and R are true but R is not the correct explanation of A.

A is true but R is false.

A is false but R is true.

Both A and R are false.

Solution

Question 2

Both A and R are true and R is the correct explanation of A.

Both A and R are true, but R is not the correct explanation of A.

A is true, but R is false.

A is false, but R is true.

Both A and R are false.

Solution

Question 3

Both A and R are true and R is the correct explanation of A.

Both A and R are true but R is not the correct explanation of A.

A is true but R is false.

A is false but R is true.

Both A and R are false.

Solution

Question 4

Both A and R are true and R is the correct explanation of A.

Both A and R are true but R is not the correct explanation of A.

A is true but R is false.

A is false but R is true.

Both A and R are false.

Solution

Question 5

Both A and R are true and R is the correct explanation of A.

Both A and R are true but R is not the correct explanation of A.

A is true but R is false.

A is false but R is true.

Both A and R are false.

Solution

Question 6

Both A and R are true and R is the correct explanation of A.

Both A and R are true but R is not the correct explanation of A.

A is true but R is false.

A is false but R is true.

Both A and R are false.

Solution

Question 7

Both A and R are true and R is the correct explanation of A.

Both A and R are true but R is not the correct explanation of A.

A is true but R is false.

A is false but R is true.

Both A and R are false.

Solution

Question 8

Both A and R are true and R is the correct explanation of A.

Both A and R are true but R is not the correct explanation of A.

A is true but R is false.

A is false but R is true.

Both A and R are false.

Solution

Question 9

Only A

Only B

Only C

None of these

All of these

Solution

Question 10

Only A

Only B

Only C

A and B

B and C

Solution

Question 11

Only A