The unit of rate constant for zero order reaction is :

Options

A. Mol `litre^-1 sec^-1`
B. Litre `mol^-1 sec^-1`
C. `Sec^-1`
D. `Mol^2 litre^-2 sec^-1`

Answer

To determine the unit of the rate constant for a zero-order reaction, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Rate Law for Zero-Order Reactions**:
- The rate of a zero-order reaction is independent of the concentration of the reactants. The rate can be expressed as:
\[ \text{Rate} = k \]
- Here, \( k \) is the rate constant.

2. **Identify the General Formula for the Rate Constant**:
- The unit of the rate constant \( k \) for any reaction can be derived from the general formula:
\[ k = \text{Concentration}^{(1-n)} \cdot \text{Time}^{-1} \]
- Where \( n \) is the order of the reaction.

3. **Substitute the Order of Reaction**:
- For a zero-order reaction, \( n = 0 \). Therefore, substituting \( n \) into the formula gives:
\[ k = \text{Concentration}^{(1-0)} \cdot \text{Time}^{-1} = \text{Concentration}^1 \cdot \text{Time}^{-1} \]

4. **Define Concentration and Time Units**:
- Concentration is typically expressed in moles per liter (mol/L).
- Time is expressed in seconds (s).

5. **Combine the Units**:
- Substituting the units into the equation:
\[ k = \frac{\text{mol}}{\text{L}} \cdot \frac{1}{\text{s}} = \frac{\text{mol}}{\text{L} \cdot \text{s}} \]

6. **Conclusion**:
- Therefore, the unit of the rate constant \( k \) for a zero-order reaction is:
\[ \text{mol} \cdot \text{L}^{-1} \cdot \text{s}^{-1} \]
- This corresponds to option 1 from the provided choices.

### Final Answer:
The unit of the rate constant for a zero-order reaction is **mol L⁻¹ s⁻¹**.

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