Question

Unit of rate constant for a zero order reaction is:

• A. mol/m$^2$·s$^{-1}$
• B. mol·s/m$^2$
• C. s$^{-1}$
• D. mol/m$^3$·s$^{-1}$

Hint:

For zero-order reactions, the rate is independent of concentration, so $k$ has units of concentration/time.

Answer 1

The Correct Option is D

Step 1: State the rate law formula.
For a reaction of order $n$, the units of the rate constant $k$ are given by: \[\text{Units of } k = \frac{\text{(concentration)}^{1-n}}{\text{time}}\]

Step 2: Substitute $n=0$ for a zero-order reaction.
\[\text{Units of } k = \frac{\text{concentration}^{1-0}}{\text{time}} = \frac{\text{concentration}}{\text{time}}\]

Step 3: Convert to standard SI units.
Given that concentration is mol/m$^3$ and time is s. \[ $\Rightarrow$ \text{Units of } k = \frac{\text{mol/m}^3}{s} = \text{mol·m$^{-3}$·s$^{-1}$}\]

Step 4: Final Answer.
The correct option is (D).