The rate constant of a reaction has same units as the rate of reaction. The reaction is of:

Options

A. zero order
B. first order
C. second order
D. none of these

Explanation

To determine the type of reaction for which the rate constant has the same units as the rate of reaction, we will analyze the different orders of reactions.

### Step-by-Step Solution:

1. **Understanding Rate of Reaction**:
The rate of a reaction is generally expressed in terms of concentration change per unit time, typically in units like mol/L/s (molarity per second).

2. **Zero-Order Reaction**:
- In a zero-order reaction, the rate of reaction is independent of the concentration of the reactants.
- The rate law can be expressed as:
\[ \text{Rate} = k \]
- Here, \( k \) is the rate constant.
- Since the rate does not depend on concentration, the units of \( k \) must be the same as the units of the rate of reaction.
- Therefore, for a zero-order reaction, the units of the rate constant \( k \) are the same as the rate of reaction, which is mol/L/s.

3. **First-Order Reaction**:
- In a first-order reaction, the rate is directly proportional to the concentration of one reactant.
- The rate law can be expressed as:
\[ \text{Rate} = k[A] \]
- Here, the units of \( k \) would be different because the rate has units of mol/L/s, and \( [A] \) has units of mol/L. Thus, the units of \( k \) would be:
\[ \text{Units of } k = \frac{\text{mol/L/s}}{\text{mol/L}} = \text{s}^{-1} \]
- Therefore, the units of the rate constant \( k \) are not the same as the rate of reaction.

4. **Second-Order Reaction**:
- In a second-order reaction, the rate is proportional to the square of the concentration of one reactant.
- The rate law can be expressed as:
\[ \text{Rate} = k[A]^2 \]
- The units of \( k \) in this case would be:
\[ \text{Units of } k = \frac{\text{mol/L/s}}{(\text{mol/L})^2} = \text{L/mol/s} \]
- Again, the units of the rate constant \( k \) are not the same as the rate of reaction.

5. **Conclusion**:
- The only reaction type where the rate constant \( k \) has the same units as the rate of reaction is the **zero-order reaction**.

### Final Answer:
The reaction is of **zero order**.

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