The unit of the rate constant $k$ for a zero order reaction is:

Solution

1. The rate law for a zero order reaction is $$\begin{array}{rl}\text{Rate}& =k[A{]}^0\\ & =k\end{array}$$.
2. The unit of rate is concentration per unit time, which is ${\text{mol L}}^{-1}{\text{s}}^{-1}$.
3. Since $\text{Rate}=k$, the unit of $k$ must be ${\text{mol L}}^{-1}{\text{s}}^{-1}$.
4. Hence the answer is (A).