A non-volatile, non-electrolyte solid solute when dissolved in \( 40 \, \text{g} \) of a solvent, the vapour pressure of the solvent decreased from \( 760 \, \text{mm Hg} \) to \( 750 \, \text{mm Hg} \). If the same solution boils at \( 320 \, \text{K} \), then the number of moles of the solvent present in the solution is ________. (Nearest integer)
[Given: boiling point of the pure solvent \( = 319.5 \, \text{K} \). \( K_b \) of the solvent \( = 0.3 \, \text{K kg mol}^{-1} \)]
When a non-volatile solute is added to the solvent, the vapour pressure of the solvent decreases by \( 10 \, \text{mm of Hg} \). The mole fraction of the solute in the solution is \( 0.2 \). What would be the mole fraction of the solvent if decreases in vapour pressure is \( 20 \, \text{mm of Hg} \)?
