Which from following gases is least soluble in water at same temperature and pressure ?

Calculate the mole fraction of solute in solution if vapour pressure of a solution and pure solvent are 27 mm Hg and 30 mm Hg respectively at 298 K.

Calculate the molar mass of nonelectrolyte solute when 6 gram of it is dissolved in 1 $\text{dm}^3$ water has osmotic pressure $2.4\ \text{atm}$ at 300 K $(R = 0.0821\ \text{atm dm}^3\ \text{K}^{-1}\ \text{mol}^{-1})$

$40$ gram nonelectrolyte solute having molar mass $180\ \text{g mol}^{-1}$ dissolved in water has osmotic pressure $2\ \text{atm}$ at $300\ \text{K}$. Calculate the volume of solution. ($\text{R} = 0.0821\ \text{atm mol}^{-1}\text{K}^{-1}$)