NEET Chemical Kinetics — Set 12

Question 1

A reaction’s rate increases by 4 times when the temperature rises from 310 K to 330 K. What is the activation energy ($ R = 8.314 \, \text{J mol}^{-1} \text{K}^{-1} $)?

Accepted Answer

$ \log \frac{k_2}{k_1} = \frac{E_a}{2.303 R} \left( \frac{T_2 - T_1}{T_1 T_2} \right) $. $ \log 4 = \frac{E_a}{2.303 \times 8.314} \left( \frac{20}{310 \times 330} \right) $. $ 0.602 = \frac{E_a \times 20}{19.147 \times 102300} $, $ E_a \approx 58,900 \, \text{J mol}^{-1} \approx 58.9 \, \text{kJ mol}^{-1} $.

Question 2

For the reaction $ 2\text{A} + 2\text{B} \to 3\text{C} $, the rate of formation of C is $ 0.15 \, \text{mol L}^{-1} \text{min}^{-1} $. What is the rate of disappearance of A?

Accepted Answer

Rate = $ -\frac{1}{2} \frac{\Delta[\text{A}]}{\Delta t} = \frac{1}{3} \frac{\Delta[\text{C}]}{\Delta t} $. Given: $ \frac{\Delta[\text{C}]}{\Delta t} = 0.15 \, \text{mol L}^{-1} \text{min}^{-1} $. Rate = $ \frac{0.15}{3} = 0.05 $, $ -\frac{\Delta[\text{A}]}{\Delta t} = 2 \times 0.05 = 0.1 \, \text{mol L}^{-1} \text{min}^{-1} $.

Question 3

For the reaction $ 3\text{A} \to 2\text{B} $, the rate of formation of B is $ 0.02 \, \text{mol L}^{-1} \text{s}^{-1} $. What is the rate of disappearance of A?

Accepted Answer

Rate = $ -\frac{1}{3} \frac{\Delta[\text{A}]}{\Delta t} = \frac{1}{2} \frac{\Delta[\text{B}]}{\Delta t} $. Given: $ \frac{\Delta[\text{B}]}{\Delta t} = 0.02 \, \text{mol L}^{-1} \text{s}^{-1} $. Rate = $ \frac{0.02}{2} = 0.01 \, \text{mol L}^{-1} \text{s}^{-1} $, so $ -\frac{\Delta[\text{A}]}{\Delta t} = 3 \times 0.01 = 0.03 \, \text{mol L}^{-1} \text{s}^{-1} $.

NEET Chemistry: Chemical Kinetics — Practice Set 12

Q1. A reaction’s rate increases by 4 times when the temperature rises from 310 K to 330 K. What is the activation energy (\( R = 8.314 \, \text{J mol}^{-1} \text{K}^{-1} \))?

Q2. For the reaction \( 2\text{A} + 2\text{B} \to 3\text{C} \), the rate of formation of C is \( 0.15 \, \text{mol L}^{-1} \text{min}^{-1} \). What is the rate of disappearance of A?

Q3. For the reaction \( 3\text{A} \to 2\text{B} \), the rate of formation of B is \( 0.02 \, \text{mol L}^{-1} \text{s}^{-1} \). What is the rate of disappearance of A?

Q4. A reaction has the rate law \( \text{Rate} = k[\text{A}]^{2/3}[\text{B}]^{2/3} \). What is the overall order?

Q5. A zero-order reaction has a rate constant of \( 2.0 \times 10^{-3} \, \text{mol L}^{-1} \text{min}^{-1} \). If the initial concentration is \( 0.1 \, \text{mol L}^{-1} \), how long will it take for 40% decomposition?

Q6. A zero-order reaction takes 120 s to reduce the concentration from \( 0.3 \, \text{mol L}^{-1} \) to \( 0.18 \, \text{mol L}^{-1} \). What is the rate constant?

Q7. A reaction’s rate increases by 64 times when the concentration of the reactant is increased by 4 times. What is the order of the reaction?

Q8. A reaction has a rate constant of \( 0.08 \, \text{s}^{-1} \). What is its order?

Q9. A first-order reaction has a half-life of 14 minutes. What percentage of the reactant decomposes in 42 minutes?

Q10. A first-order reaction has a half-life of 30 minutes. What fraction of the reactant remains after 90 minutes?