Assertion : The overall order of the reaction is the sum of the exponents of all the reactants in the rate expression.
Reason: There are many higher order reactions.

Options

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

Explanation

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

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "The overall order of the reaction is the sum of the exponents of all the reactants in the rate expression."
- In a chemical reaction, the rate law is expressed in terms of the concentrations of the reactants raised to a power (the order with respect to each reactant). The overall order of the reaction is indeed the sum of these powers (exponents).

2. **Example of Rate Expression**:
- Consider a hypothetical reaction:
\[ aA + bB \rightarrow products \]
- The rate expression can be written as:
\[ \text{Rate} = k[A]^m[B]^n \]
- Here, \( m \) and \( n \) are the orders with respect to reactants A and B, respectively. The overall order of the reaction is \( m + n \).

3. **Conclusion on Assertion**:
- Since the assertion correctly describes how to determine the overall order of a reaction, we conclude that the assertion is **True**.

4. **Understanding the Reason**:
- The reason states that "There are many higher order reactions."
- Higher order reactions refer to reactions that have an overall order greater than 2. However, the statement does not accurately explain or relate to the assertion.

5. **Analyzing the Reason**:
- While higher order reactions do exist, the reason does not provide a valid justification for the assertion. In fact, the occurrence of higher order reactions is limited by the likelihood of effective collisions between reactant molecules. As the order increases, the chances of effective collisions decrease, making higher order reactions less common.

6. **Conclusion on Reason**:
- Therefore, the reason is **False** because it does not correctly support the assertion.

### Final Conclusion:
- The assertion is **True** and the reason is **False**. Thus, the correct answer is that the assertion is true, but the reason is false.

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