Question 91
For a zero-order reaction, if the initial concentration is 0.4 M and the rate constant kk is 0.1 M/s, how long will it take for the concentration to reach 0?
A) 2 s
B) 4 s
C) 8 s
D) 16 s
Answer: B) 4 s
Question 92
In an elementary reaction, what does the term “molecularity” refer to?
A) The total number of products formed
B) The number of reactant molecules involved in the step
C) The rate of the reaction
D) The temperature at which the reaction occurs
Answer: B) The number of reactant molecules involved in the step
Explanation: Molecularity specifically refers to how many molecules are involved in an elementary step of the reaction.
Question 93
The rate constant kk for a reaction is influenced by:
A) The concentration of reactants
B) The temperature
C) The presence of catalysts
D) Both B and C
Answer: D) Both B and C
Explanation: The rate constant is primarily influenced by temperature and the presence of catalysts.
Question 94
If the rate law is given as Rate=k[A]0[B]1Rate=k[A]0[B]1, what can be concluded about reactant A?
A) It has no effect on the rate.
B) It increases the rate significantly.
C) It is the limiting reactant.
D) It is the catalyst.
Answer: A) It has no effect on the rate.
Explanation: A concentration raised to the power of zero means it does not influence the rate of the reaction.
Question 95
In a bimolecular reaction, if the concentration of both reactants is doubled, how does the rate change?
A) It remains the same
B) It doubles
C) It quadruples
D) It increases eightfold
Answer: C) It quadruples
Question 96
In the context of reaction kinetics, what is meant by “order of a reaction”?
A) The number of reactants
B) The power to which the concentration of a reactant is raised in the rate law
C) The total time required for the reaction
D) The speed of the reaction
Answer: B) The power to which the concentration of a reactant is raised in the rate law
Explanation: The order of a reaction refers to the exponents in the rate law, indicating how the rate depends on the concentration of each reactant.
Question 97
If a reaction’s rate is described by Rate=k[A]2[B]0Rate=k[A]2[B]0, which of the following statements is true?
A) The reaction is zero-order with respect to A.
B) The reaction is first-order with respect to B.
C) The concentration of B has no effect on the rate.
D) The reaction is second-order with respect to both A and B.
Answer: C) The concentration of B has no effect on the rate.
Explanation: Since B has an exponent of 0, its concentration does not influence the rate of the reaction.
Question 98
For a reaction that is first-order, the integrated rate law can be expressed as:
A) [A]=[A]0−kt
B) [A]=[A]0e−kt
C) ln[A]=ln[A]0−kt
D) Both B and C
Answer: D) Both B and C
Explanation: Both expressions represent the integrated rate laws for first-order reactions.
Question 99
The units of the rate constant kk for a zero-order reaction are:
A) M/s
B) M²/s
C) 1/M·s
D) M/s²
Answer: A) M/s
Explanation: For zero-order reactions, the rate is constant and the unit of kk is concentration per time, which is M/s.
Question 100
In the context of chemical kinetics, which statement is correct?
A) Molecularity can be a fraction.
B) The order of a reaction is always equal to its molecularity.
C) The rate constant changes with concentration.
D) Molecularity is defined for elementary reactions only.
Answer: D) Molecularity is defined for elementary reactions only.
Explanation: Molecularity is specific to elementary steps in a reaction mechanism and cannot be a fraction.
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