Class 12 chemistry MCQs with answers are provided here for chapter 4 Chemical Kinetics. These MCQs are based on the CBSE board curriculum and correspond to the most recent Class 12 chemistry syllabus. By practising these Class 12 Multiple choice questions, students will be able to quickly review all of the ideas covered in the chapter and prepare for the Class 12 CBSE Board Annual examinations as well as other entrance exams such as NEET and JEE.
Chemical Kinetics MCQs with Explanation Class 12 CBSE Chemistry Worksheet
1. The study of reaction kinetics is called __________.
a) Rate of reaction
b) Mechanism of reaction
c) Factors which affect the rate of reaction
d) All of the mentioned
Answer: d
Explanation: Reaction kinetics is the study of reaction rates, mechanisms, and the factors that influence reaction rates.
2. The reaction rate constant can be defined as the rate of reaction when each reactant’s concentration is ___________.
a) Zero
b) Unity
c) Doubled the initial concentration
d) Infinite
Answer: b
Explanation: The reaction rate constant can be defined as the rate of the reaction when all of the reactants’ concentrations are unity. The rate of a chemical reaction is quantified by a reaction rate constant, or reaction rate coefficient, k.
3. Which of the following is the right temperature coefficient (n) expression?
a) n = Rate constant at T + 10°/Rate constant at T°
b) n = Rate constant at T + 20°/Rate constant at T°
c) n = Rate constant at T + 30°/Rate constant at T°
d)n = Rate constant at T + 40°/Rate constant at T°
Answer: a
Explanation: The effect of temperature on a reaction’s pace is commonly stated in terms of the temperature coefficient, which is defined by the equation:
Temperature coefficient (n) = T + 10° (308 K) rate constant/T° rate constant (298 K).
4. When the temperature rises, what happens to the peak of the curve in the Maxwell-Boltzmann distribution graph?
a) Shifts forward and upward
b) Shifts forward and downward
c) Shifts backwards and upward
d) Shifts backwards and downward
Answer: b
Explanation: The peak moves ahead but downward as the temperature rises. This is because when the temperature rises, the most probable kinetic energy rises, while the percentage of molecules with the most probable kinetic energy drops.
5. Plotting a graph between temperature and reaction rates can reveal the temperature dependence of reaction rates.
a) Concentration of reactants and temperature
b) Concentration of products and temperature
c) Rate constant and temperature
d) Rate of catalysis and temperature
Answer: c
Explanation: Plotting a graph between rate constant and temperature for various reactions can be used to investigate the temperature dependence of reaction rates.
6. What effect does temperature have on the half-life of a first-order reaction?
a) It increases
b) It decreases
c) It remains the same
d) Both increases as well as decrease
Answer: b
Explanation: For the first-order reaction, the rate constant increases on increasing temperature. But for the half-life of a first-order reaction, the rate constant is inversely proportional to half-life; thus, on increasing temperature, half-life decreases.
7. Only a simple homogeneous reaction requires which of the following methods?
a) Integration method
b) Half-life period method
c) Graphical method
d) Ostwald’s isolation method
Answer: a
Explanation: For complex reactions, the integration method leads to incorrect conclusions. But the integration method is suitable for simple homogeneous reactions.
8. In 30 minutes, a first-order reaction is 50% complete. Calculate the amount of time it took to complete 87.5 percent of the reaction.
a) 30 minutes
b) 60 minutes
c) 90 minutes
d) 120 minutes
Answer: c
Explanation: In 30 minutes, the reaction is 50% complete. As a result, t1/2 = 30 minutes.
In two half-lives, 75% of the process is accomplished. As a result, t = 2 ×30 = 60 minutes.
In three half-lives, 87.5 percent of the reaction is finished.
Hence, t = 3 × 30 = 90 minutes.
9. In a reaction, what is the driving force?
a) Energy given
b) Energy released
c) Free energy
d) None of the mentioned
Answer: c
Explanation: The change in free energy, which is related to the equilibrium constant, is the reaction’s driving force (K).
10. What is the heat of reaction for ethyl acetate hydrolysis?
a) Greater than zero
b) Less than zero
c) Zero
d) None of the mentioned
Answer: c
Explanation: The equilibrium position of ethyl acetate hydrolysis was demonstrated to be temperature independent. Because the bonds broken and created are of the same kind, calculating the heat of reaction using the bond energies technique yields a value of zero.