Question

The unit of velocity constant for a first-order reaction is:

• A. \( \text{sec}^{-1} \)
• B. \( \text{litre sec}^{-1} \)
• C. \( \text{mol sec}^{-1} \)
• D. \( \text{litre mol}^{-1} \text{sec}^{-1} \)

Hint:

The unit of a rate constant depends on the order of the reaction: - Zero-order: \( \text{mol L}^{-1} \text{sec}^{-1} \) - First-order: \( \text{sec}^{-1} \) - Second-order: \( \text{L mol}^{-1} \text{sec}^{-1} \)

Answer 1

The Correct Option is A

Step 1: Understanding the Unit of First-Order Reaction For a first-order reaction, the rate equation is: \[ \text{Rate} = k[A] \] where \( k \) is the rate constant. Since rate has units of \( \text{mol L}^{-1} \text{sec}^{-1} \) and concentration has units of \( \text{mol L}^{-1} \), the unit of \( k \) is: \[ \frac{\text{mol L}^{-1} \text{sec}^{-1}}{\text{mol L}^{-1}} = \text{sec}^{-1} \]