A : At constant volume on increasing temperature the collision frequency increases.
R : Collision frequency `prop` temperature of gas.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then Mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4).

Answer

To solve the question, we need to analyze both the assertion (A) and the reason (R) provided.

### Step 1: Understand the Assertion (A)
The assertion states that "At constant volume, on increasing temperature, the collision frequency increases."

- **Explanation**: When the temperature of a gas increases, the kinetic energy of the gas molecules also increases. Since the volume is constant, the molecules will move faster due to the increased kinetic energy. As a result, the frequency of collisions between the gas molecules will increase.

### Step 2: Understand the Reason (R)
The reason states that "Collision frequency is proportional to the temperature of gas."

- **Explanation**: While the collision frequency does increase with temperature, it is important to note that this relationship is not straightforward. The collision frequency is influenced by several factors, including the volume of the gas and the speed of the molecules. At constant volume, the increase in temperature leads to an increase in molecular speed, which in turn increases collision frequency. However, the statement that collision frequency is directly proportional to temperature is not entirely accurate without considering other conditions (like constant volume).

### Step 3: Conclusion
- The assertion (A) is **correct**: Increasing temperature at constant volume does lead to an increase in collision frequency.
- The reason (R) is **incorrect**: Collision frequency is not solely proportional to temperature; it also depends on other factors such as volume and molecular speed.

### Final Answer
Thus, the assertion is true, and the reason is false. Therefore, the correct option is that assertion A is true, and reason R is false.

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