A gas 'X' when dissolved in water, heat is evolved. Then solubility of 'X' will increase:

Options

A. Low pressure, high temperature
B. Low pressure , low temperature
C. High pressure, high temperature
D. High pressure, low temperature

Explanation

To solve the question regarding the solubility of gas 'X' in water when heat is evolved, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Nature of the Process:**
- The question states that when gas 'X' is dissolved in water, heat is evolved. This indicates that the dissolution of gas 'X' is an exothermic process.

2. **Understand Exothermic Reactions:**
- In an exothermic reaction, heat is released. According to Le Chatelier's principle, if a reaction is exothermic, lowering the temperature will favor the forward reaction (the dissolution of gas 'X') and increase the solubility of the gas.

3. **Temperature Effect on Solubility:**
- Since the dissolution process is exothermic, decreasing the temperature will shift the equilibrium to the right, leading to an increase in the solubility of gas 'X'. Therefore, low temperature conditions will enhance the solubility of gas 'X'.

4. **Pressure Effect on Solubility:**
- According to Henry's Law, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. Therefore, increasing the pressure will also increase the solubility of gas 'X'.

5. **Combine the Effects:**
- To maximize the solubility of gas 'X', we need to consider both temperature and pressure. The ideal conditions for high solubility of gas 'X' would be low temperature and high pressure.

6. **Conclusion:**
- Based on the analysis, the solubility of gas 'X' will increase under conditions of low temperature and high pressure.

### Final Answer:
The solubility of gas 'X' will increase under conditions of **low temperature and high pressure**.

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