Statement I: The solubility of the gas in a liquid increases with increase of pressure.

Statement II: The solubility of a gas in a liquid, expressed by mole fraction of gas in the liquid solution at equilibrium, is directly proportional to the pressure of the gas.

If both statements are CORRECT, and Statement II is the CORRECT explanation of Statement I.

The correct answer is:

1. If both statements are CORRECT, and Statement II is the CORRECT explanation of Statement I.

Statement I: The solubility of the gas in a liquid increases with an increase in pressure.

This statement is correct. 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. As the pressure increases, more gas molecules are forced into the liquid, resulting in higher solubility.

Statement II: The solubility of a gas in a liquid, expressed by the mole fraction of gas in the liquid solution at equilibrium, is directly proportional to the pressure of the gas.

This statement is also correct. The solubility of a gas in a liquid can be expressed by the mole fraction of the gas in the liquid solution at equilibrium. Henry's law states that the mole fraction of the gas is directly proportional to the partial pressure of the gas. Therefore, as the pressure of the gas increases, the mole fraction of the gas in the liquid solution also increases.

Statement II provides the correct explanation for Statement I, as it explains the relationship between solubility and pressure using Henry's law. Therefore, the correct answer is 1. If both statements are CORRECT, and Statement II is the CORRECT explanation of Statement I.