In which of the following salts,the solubility increases appreciably with an increase in temperature?

The solubility of a gas in a liquid increases with:

Give an example of a solution where both the solute and the solvent are in the gaseous state.

Calculate $K_H$ when $2 \ mmol$ of $O_2$ dissolve in $540 \ mL$ of water at $27 \ ^oC$ temperature. Given $P_{O_2} = 2 \times 10^{-8} \ bar$.

Given below are two statements:
Statement $I$: The Henry's law constant $K_{H}$ is constant with respect to variations in solution's concentration over the range for which the solution is ideally dilute.
Statement $II$: $K_{H}$ does not differ for the same solute in different solvents.
In the light of the above statements, choose the correct answer from the options.

$A$ gas $X$ is dissolved in water at $2 \ bar$ pressure. Its mole fraction in the solution is $0.02$. Find the mole fraction of water in the solution when the pressure of the gas is doubled at the same temperature.