Assertion : Gases become denser at high pressure .
Reason : At high pressures , gases deviate from Boyle's law .

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 assertion-reason question, we will analyze both the assertion and the reason provided, and determine their validity and relationship.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that gases become denser at high pressure.
- Density is defined as mass per unit volume (Density = Mass/Volume).
- When pressure is increased, the volume of a gas decreases (as per Boyle's law), assuming the temperature remains constant.

2. **Analyzing the Effect of High Pressure**:
- At high pressure, gas molecules are forced closer together, which leads to a decrease in volume.
- Since density is inversely proportional to volume (Density ∝ 1/Volume), a decrease in volume results in an increase in density.
- Therefore, the assertion that gases become denser at high pressure is **true**.

3. **Understanding the Reason**:
- The reason states that at high pressures, gases deviate from Boyle's law.
- Boyle's law states that for a given mass of gas at constant temperature, the pressure of the gas is inversely proportional to its volume (P ∝ 1/V).
- At high pressures, real gases do not behave ideally due to intermolecular forces and the volume occupied by gas molecules themselves, leading to deviations from Boyle's law.

4. **Validity of the Reason**:
- The reason provided is also **true** because it correctly states that gases deviate from Boyle's law at high pressures.
- However, while the reason is true, it does not explain why gases become denser at high pressure. It merely states a fact about gas behavior under high pressure.

5. **Conclusion**:
- Both the assertion and the reason are true, but the reason does not provide a correct explanation for the assertion.
- Therefore, the correct answer is that both assertion and reason are true, but the reason is not the correct explanation of the assertion.

### Final Answer:
- **Both assertion and reason are true, but reason is not the correct explanation of the assertion.**