Assertion : Instantaneous rate of reaction is equal to dx/dt .
Reason : It is the rate of reaction at any particular instant of time

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion
B. If both assertion and reason are true but reason is not the correct explanation of the assertion
C. If assertion is true but reason is false
D. If assertion and reason both are false .

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

**Assertion:** Instantaneous rate of reaction is equal to dx/dt.

**Reason:** It is the rate of reaction at any particular instant of time.

### Step-by-Step Solution:

1. **Understanding the Assertion:**
- The assertion states that the instantaneous rate of reaction can be represented mathematically as \( \frac{dx}{dt} \).
- Here, \( dx \) represents the change in concentration of reactants or products, and \( dt \) represents the change in time.
- Thus, \( \frac{dx}{dt} \) is indeed a valid expression for the instantaneous rate of reaction.

2. **Understanding the Reason:**
- The reason provided states that the instantaneous rate of reaction is the rate at a particular instant of time.
- This is a correct interpretation of what an instantaneous rate means. It reflects how the concentration of reactants or products changes at a specific moment, rather than over an interval of time.

3. **Conclusion:**
- Both the assertion and the reason are correct.
- Furthermore, the reason correctly explains the assertion, as it clarifies what is meant by the instantaneous rate of reaction.

### Final Answer:
Both the assertion and the reason are correct, and the reason is the correct explanation of the assertion.