Question

The unit of rate constant for a zero order reaction is -

• A. $s^{-1}$
• B. $mol \, L^{-1} s^{-1}$
• C. $L \, mol^{-1} s^{-1}$
• D. $L^2 \, mol^{-2} s^{-1}$

Answer 1

The Correct Option is B

To determine the unit of the rate constant for a zero-order reaction, we need to understand the rate law expression for zero-order reactions.

In general, the rate of a reaction can be represented as:

\text{Rate} = k [A]^n

where:

• k is the rate constant.
• [A] is the concentration of the reactant.
• n is the order of the reaction.

For a zero-order reaction (n = 0), the rate equation simplifies to:

\text{Rate} = k \times [A]^0 = k

This indicates that the rate of the reaction is independent of the concentration of the reactant.

The units of the rate are typically expressed as concentration/time, which for a zero-order reaction would be:

• mol \, L^{-1} \, s^{-1}

Thus, the units of the rate constant k for a zero-order reaction are the same as the units of the rate, which is mol \, L^{-1} \, s^{-1}.

Therefore, the correct answer is:

mol \, L^{-1} \, s^{-1}

This unit matches the option mol \, L^{-1} s^{-1} given in the question, confirming its correctness.