Which of the following statement is incorrect ?

Options

A. Unit of rate of disappearance is `Ms^(-1)`
B. Unit of rate of reaction is `Ms^(-1)`
C. Unit of rate constant `k` is depend on order
D. Unit of `k` for first order reaction is `Ms^(-1)`

Answer

To determine which statement is incorrect regarding chemical kinetics, we will analyze each statement one by one.

### Step-by-Step Solution:

1. **Understanding Rate of Disappearance**:
- The rate of disappearance of a reactant in a chemical reaction is defined as the change in concentration of that reactant over time. The unit for concentration is molarity (mol/L), and since time is measured in seconds, the unit for the rate of disappearance is molarity per second (M/s or molarity second inverse).
- **Conclusion**: The statement regarding the unit of rate of disappearance being molarity second inverse is correct.

2. **Rate of Reaction**:
- The rate of reaction is also defined similarly to the rate of disappearance. It measures how quickly reactants are converted into products, and thus it also has the same unit of molarity second inverse.
- **Conclusion**: The statement regarding the unit of rate of reaction being molarity second inverse is correct.

3. **Unit of Rate Constant (k)**:
- The unit of the rate constant (k) does depend on the order of the reaction. For example:
- Zero-order: M/s
- First-order: s^-1
- Second-order: M^-1s^-1
- Therefore, the unit of k varies with the order of the reaction.
- **Conclusion**: The statement that the unit of rate constant k is dependent on the order is correct.

4. **Unit of k for First Order Reaction**:
- For a first-order reaction, the unit of the rate constant k is not molarity second inverse (M/s). Instead, it is s^-1 (inverse seconds).
- **Conclusion**: The statement that the unit of k for the first-order reaction is molarity second inverse is incorrect.

### Final Answer:
The incorrect statement is **D**: "The unit of k for the first order reaction is molarity second inverse."

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