Chapter Exam

Chapter 7: Chemical Kinetics — Online MCQ Test

Q: What is the unit of rate constant for a first-order reaction?

Answer: B. s^-1 — For a first-order reaction, the rate constant has the unit time^-1, which is s^-1.

Q: The molecularity of an elementary reaction can be defined as the number of:

Answer: C. reactant species taking part in a single step — Molecularity refers to the number of reacting species involved in one elementary step.

Q: For a second-order reaction involving a single reactant A, which integrated rate law is correct?

Answer: B. 1/[A] = 1/[A]0 + kt — For a second-order reaction in one reactant, the integrated rate law is 1/[A] = 1/[A]0 + kt.

Q: A zero-order reaction has a rate constant k = 0.02 mol L^-1 s^-1. If the initial concentration is 0.10 mol L^-1, the time required for complete consumption is:

Answer: B. 5 s — For a zero-order reaction, t = [A]0/k. So t = 0.10/0.02 = 5 s.

CHEMISTRY · CLASS 12th · Tamil Nadu State Board

Practice Chapter 7: Chemical Kinetics with a free chapter-wise online MCQ test for Tamil Nadu State Board CLASS 12th CHEMISTRY. This chapter covers: Focusing on reaction rates this chapter details rate laws order and molecularity of chemical reactions. It covers integrated rate equations half-life determination Arrhenius equati.... AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter 7: Chemical Kinetics — Important Questions & Answers (FAQ)

Frequently asked questions from Tamil Nadu State Board CLASS 12th CHEMISTRY — Chapter 7: Chemical Kinetics, with answers and explanations. These are sample questions; the exam has its own separate question set.

What is the unit of rate constant for a first-order reaction?

A. mol L^-1 s^-1
B. s^-1 ✓
C. L mol^-1 s^-1
D. mol^2 L^-2 s^-1

Answer: B. s^-1
For a first-order reaction, the rate constant has the unit time^-1, which is s^-1.

The molecularity of an elementary reaction can be defined as the number of:

A. products formed in the reaction
B. steps in the mechanism
C. reactant species taking part in a single step ✓
D. collisions per second

Answer: C. reactant species taking part in a single step
Molecularity refers to the number of reacting species involved in one elementary step.

For a second-order reaction involving a single reactant A, which integrated rate law is correct?

A. ln[A] = ln[A]0 - kt
B. 1/[A] = 1/[A]0 + kt ✓
C. [A] = [A]0 - kt
D. t1/2 = 0.693/k

Answer: B. 1/[A] = 1/[A]0 + kt
For a second-order reaction in one reactant, the integrated rate law is 1/[A] = 1/[A]0 + kt.

A reaction is slow at room temperature but becomes much faster on heating. Which reason best explains this?

A. Heating decreases activation energy directly
B. Heating increases the fraction of molecules having energy greater than activation energy ✓
C. Heating always increases molecularity
D. Heating changes the products formed

Answer: B. Heating increases the fraction of molecules having energy greater than activation energy
On heating, more molecules acquire energy equal to or greater than the activation energy, so the reaction rate increases.

A zero-order reaction has a rate constant k = 0.02 mol L^-1 s^-1. If the initial concentration is 0.10 mol L^-1, the time required for complete consumption is: