Question

The unit of rate constant of a zero order reaction is —

• A. \( min^{-1} \)
• B. \( L\ mol^{-1}\ min^{-1} \)
• C. \( mol\ L^{-1}\ min^{-1} \)
• D. Dimensionless

Hint:

For zero order rate equals k, so k has the units of rate, concentration over time.

Answer 1

The Correct Option is C

Step 1: For a zero order reaction the rate does not depend on concentration: rate \(= k[A]^{0} = k\).
Step 2: This means the rate constant \(k\) has the same units as the rate itself.
Step 3: Rate is measured as change in concentration per unit time, so its units are \( mol\ L^{-1}\ min^{-1} \) (or \( mol\ L^{-1}\ s^{-1} \)).
\[ k = \text{rate} = mol\ L^{-1}\ min^{-1} \]
Step 4: Therefore the unit of the zero order rate constant is \( mol\ L^{-1}\ min^{-1} \).
Correct answer: (iii). Option (i) is for first order, option (ii) is for second order.