CHEMICAL KINETICS - 20 NEET MCQs

 

Chemical Kinetics - NEET Level MCQs

1. The rate of a reaction doubles when the temperature is increased by 10°C. The activation energy (Ea) of the reaction is approximately:
   a) 34.2 kJ/mol
   b) 54.0 kJ/mol
   c) 68.4 kJ/mol
   d) 15.0 kJ/mol


2. The unit of rate constant for a first-order reaction is:
   a) mol L⁻¹ s⁻¹
   b) s⁻¹
   c) mol⁻¹ L s⁻¹
   d) L mol⁻¹ s


3. For a zero-order reaction, the half-life (t_1/2) is proportional to:
   a) [A]₀
   b) 1/[A]₀
   c) [A]₀²
   d) Independent of [A]₀


4. Which of the following statements is correct about the rate constant?
   a) It changes with temperature
   b) It depends on concentration
   c) It is dimensionless
   d) It decreases with catalyst


5. The slope of ln [A] vs time for a first-order reaction gives:
   a) −k
   b) k
   c) 1/k
   d) −1/k


6. For a reaction A → B, the rate law is rate = k[A]². If the concentration of A is doubled, the rate increases by:
   a) 2 times
   b) 3 times
   c) 4 times
   d) 8 times


7. The half-life of a first-order reaction depends on:
   a) Initial concentration
   b) Temperature only
   c) Catalyst concentration
   d) Pressure


8. In the Arrhenius equation k = A e^−Ea/RT, A represents:
   a) Activation energy
   b) Frequency factor
   c) Rate of reaction
   d) Gibbs free energy


9. Which of the following plots is linear for a first-order reaction?
   a) [A] vs time
   b) 1/[A] vs time
   c) ln[A] vs time
   d) [A]² vs time


10. For a reaction having rate = k[A][B]², the overall order is:
    a) 1
    b) 2
    c) 3
    d) 0


11. If the rate of a reaction remains constant throughout, the reaction is:
    a) First order
    b) Second order
    c) Zero order
    d) Fractional order


12. In a first-order reaction, the time required for 75% completion is (t_1/2 = 693/k):
    a) 2t_1/2
    b) 3t_1/2
    c) t_1/2/2
    d) 4t_1/2


13. If the concentration of a reactant is increased, the rate of a zero-order reaction:
    a) Increases
    b) Decreases
    c) Remains same
    d) Becomes zero


14. The rate constant of a reaction at 600 K is double that at 500 K. The activation energy is approximately:
    a) 34 kJ/mol
    b) 55 kJ/mol
    c) 69 kJ/mol
    d) 12 kJ/mol


15. The dimension of rate constant for a second-order reaction is:
    a) L mol⁻¹ s⁻¹
    b) mol L⁻¹ s⁻¹
    c) s⁻¹
    d) mol⁻¹ L² s⁻¹


16. The rate of a chemical reaction depends on:
    a) Temperature
    b) Concentration
    c) Nature of reactants
    d) All of these


17. For a reaction A → B + C, the rate of formation of B is 2 × 10⁻³ mol L⁻¹ s⁻¹. The rate of disappearance of A is:
    a) 1 × 10⁻³
    b) 2 × 10⁻³
    c) 4 × 10⁻³
    d) 0.5 × 10⁻³


18. The activation energy of a reaction can be determined from the slope of the plot between:
    a) ln k and T
    b) ln k and 1/T
    c) k and T
    d) k and 1/T


19. In a chemical reaction, a catalyst:
    a) Increases activation energy
    b) Decreases activation energy
    c) Changes enthalpy
    d) Shifts equilibrium position


20. For a first-order reaction, the rate constant at 27°C is 3 × 10⁻³ s⁻¹. The half-life of the reaction is:
    a) 231 s
    b) 100 s
    c) 693 s
    d) 347 s

Answers & Solutions:

1-b) Ea ≈ 54 kJ/mol using rule of thumb (rate doubles per 10°C ≈ 50–60 kJ/mol).
2-b) First order → s⁻¹.
3-a) For zero order, t₁/₂ ∝ [A]₀.
4-a) k changes with temperature (Arrhenius equation).
5-a) Slope = −k for ln[A] vs time.
6-c) Rate ∝ [A]² → doubling → 4× rate.
7-b) Depends only on temperature (k).
8-b) A = frequency factor.
9-c) ln[A] vs time is linear for first order.
10-c) Order = 1 + 2 = 3.
11-c) Zero-order → constant rate.
12-b) 75% completion = 2t₁/₂ (from ln 4 = 2 ln 2).
13-c) Zero-order → rate = k, independent of [A].
14-b) Ea ≈ 55 kJ/mol (using temperature dependence).
15-a) Second order → L mol⁻¹ s⁻¹.
16-d) All of these affect rate.
17-b) Stoichiometrically same → rate of disappearance = 2 × 10⁻³.
18-b) ln k vs 1/T slope = −Ea/R.
19-b) Catalyst lowers activation energy.
20-a) t₁/₂ = 0.693/k = 0.693/(3×10⁻³) = 231 s.