Chapter Exam

Chapter-3 Chemical Kinetics — Online MCQ Test

Q: The rate of reaction is defined as the change in concentration of reactants or products per unit time. Which of the following is the SI unit of rate of reaction?

Answer: A. mol L⁻¹ s⁻¹ — Rate of reaction is expressed as change in molarity per unit time, hence the SI unit is mol L⁻¹ s⁻¹ (or mol dm⁻³ s⁻¹).

Q: A reaction has a rate law: Rate = k[A][B]. What is the overall order of this reaction?

Answer: C. Second order — Overall order = sum of powers of concentration terms = 1 + 1 = 2 (second order).

Q: A reaction has an activation energy of 100 kJ/mol. If the temperature is raised such that the rate constant doubles, the ratio of average kinetic energy at T₂ to T₁ approximately equals:

Answer: B. 1.05 — Using Arrhenius equation and the given conditions: ln(2) = (100000/8.314)(1/T₁ - 1/T₂); The ratio of kinetic energies ≈ T₂/T₁ ≈ 1.05.

CHEMISTRY · Grade 12 · CBSE(NCERT)

Practice Chapter-3 Chemical Kinetics with a free chapter-wise online MCQ test for CBSE(NCERT) Grade 12 CHEMISTRY. This chapter covers: rate of reaction - factors affecting rates - integrated rate laws - collision theory. AI-generated questions from basic to board-exam level, with instant results and explanations.

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Chapter-3 Chemical Kinetics — Important Questions & Answers (FAQ)

Frequently asked questions from CBSE(NCERT) Grade 12 CHEMISTRY — Chapter-3 Chemical Kinetics, with answers and explanations. These are sample questions; the exam has its own separate question set.

The rate of reaction is defined as the change in concentration of reactants or products per unit time. Which of the following is the SI unit of rate of reaction?

A. mol L⁻¹ s⁻¹ ✓
B. mol s⁻¹
C. L mol⁻¹ s
D. mol L⁻¹ min⁻¹

Answer: A. mol L⁻¹ s⁻¹
Rate of reaction is expressed as change in molarity per unit time, hence the SI unit is mol L⁻¹ s⁻¹ (or mol dm⁻³ s⁻¹).

What is meant by the term 'order of reaction'?

A. The sequence in which reactants are written in the chemical equation
B. The sum of powers of concentrations in the rate law expression ✓
C. The number of reactant molecules involved in an elementary step
D. The total number of reactants in the reaction

Answer: B. The sum of powers of concentrations in the rate law expression
Order of reaction is defined as the sum of the powers of concentration terms in the rate law expression, determined experimentally.

A reaction has a rate law: Rate = k[A][B]. What is the overall order of this reaction?

A. Zero order
B. First order
C. Second order ✓
D. Third order

Answer: C. Second order
Overall order = sum of powers of concentration terms = 1 + 1 = 2 (second order).

A reaction mechanism involves two steps: (1) A + B → C (fast) and (2) C → D + E (slow). What is the rate-determining step and the overall reaction?

A. Rate-determining step is (1); Overall: A + B → D + E
B. Rate-determining step is (2); Overall: A + B + C → C + D + E
C. Rate-determining step is (2); Overall: A + B → D + E ✓
D. Rate-determining step is (1); Overall: A + B → C → D + E

Answer: C. Rate-determining step is (2); Overall: A + B → D + E
The slow step is the rate-determining step. Adding both steps and canceling intermediates (C): A + B → D + E is the overall reaction.

A reaction has an activation energy of 100 kJ/mol. If the temperature is raised such that the rate constant doubles, the ratio of average kinetic energy at T₂ to T₁ approximately equals:

A. 1.01
B. 1.05 ✓
C. 1.10
D. 1.15

Answer: B. 1.05
Using Arrhenius equation and the given conditions: ln(2) = (100000/8.314)(1/T₁ - 1/T₂); The ratio of kinetic energies ≈ T₂/T₁ ≈ 1.05.