A: Solubility of gas increases on increasing pressure.
R: Solubility of gas decreases on decreasing the temperature.

Answer

To analyze the given statements, we will break down the assertion and reason provided in the question.

### Step 1: Analyze the Assertion
The assertion states: "Solubility of gas increases on increasing pressure."

- According to **Henry's Law**, the solubility of a gas in a liquid is directly proportional to the pressure of that gas above the liquid. This means that as the pressure increases, more gas molecules are forced into the liquid, thus increasing solubility.

**Conclusion for Assertion**: The assertion is **true**.

### Step 2: Analyze the Reason
The reason states: "Solubility of gas decreases on decreasing the temperature."

- The solubility of gases in liquids is generally affected by temperature. As the temperature decreases, the kinetic energy of gas molecules decreases, allowing more gas to dissolve in the liquid. Conversely, when the temperature increases, the solubility of gases typically decreases because gas molecules have higher kinetic energy and are more likely to escape from the liquid.

**Conclusion for Reason**: The reason is **false** because it incorrectly states that solubility decreases with a decrease in temperature.

### Final Conclusion
- The assertion is **true**.
- The reason is **false**.

### Summary
- Assertion (A): True
- Reason (R): False