Identify the order of the two reactions whose rate constants are given below:
(i) $k = 2.3 × 10^{-5}\, L\, mol\,^{-1} s^{-1}$
(ii) $k= 3 × 10^{-4} s^{-1}$
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (i) Second order, (ii) First order
The order of a reaction can be identified from the units of the rate constant (k).
- Second-order reaction:
k has units of L mol⁻¹ s⁻¹ - First-order reaction:
k has units of s⁻¹
Now, given:
- (i) $k = 2.3 \times 10^{-5}\ \text{L mol}^{-1}\text{s}^{-1}$
→ Second-order reaction - (ii) $k = 3 \times 10^{-4}\ \text{s}^{-1}$
→ First-order reaction