Assertion (A): The molecularity of a reaction is a whole number other than zero, but generally less than 3
The order of a reaction is always whole number

Options

A. Both (A) and (R) are true (R) is the correct explanation to (A)
B. Both (A) and (R) are true but (R) is not the correct explanation to (A)
C. (A) is true but (R) is false
D. Both (A) and (R) are false

Explanation

To analyze the assertion and reason provided in the question, we will break down the concepts of molecularity and order of a reaction step by step.

### Step 1: Understanding Molecularity
- **Definition**: Molecularity refers to the number of reactant molecules that collide to form products in a single reaction event. It is always a whole number greater than zero.
- **Types**:
- Unimolecular: Involves one reactant molecule (e.g., A → products).
- Bimolecular: Involves two reactant molecules (e.g., A + B → products).
- Trimolecular: Involves three reactant molecules (e.g., A + B + C → products).
- **General Rule**: Molecularity is generally less than or equal to 3, with unimolecular and bimolecular reactions being the most common.

### Step 2: Evaluating the Assertion
- The assertion states that "the molecularity of a reaction is a whole number other than zero, but generally less than 3."
- This statement is **true** because molecularity is defined as a whole number (1, 2, or 3) and cannot be zero.

### Step 3: Understanding Reaction Order
- **Definition**: The order of a reaction is the sum of the powers of the concentration terms in the rate law expression. It can be determined experimentally.
- **Types**:
- Zero-order: Rate is constant and does not depend on the concentration of reactants.
- First-order: Rate depends linearly on the concentration of one reactant.
- Second-order: Rate depends on the square of the concentration of one reactant or the product of the concentrations of two reactants.
- Fractional and negative orders are also possible.

### Step 4: Evaluating the Reason
- The reason states that "the order of a reaction is always a whole number."
- This statement is **false** because the order of a reaction can be a whole number, a fraction, or even negative, depending on the reaction and how it is experimentally determined.

### Conclusion
- The assertion is true, while the reason is false.
- Therefore, the correct answer to the question is that the assertion is true, and the reason is false.

### Final Answer
- Assertion (A) is true, and the reason is false.

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