The vapour pressure of a solvent decreases by 2.5 mm Hg by adding a solute. What is the mole fraction of solute? (Vapour pressure of pure solvent is 250 mm Hg)

Molal depression constant for a liquid is $$2.77^{\circ} \mathrm{C} ~\mathrm{kg} ~\mathrm{mol}^{-1}$$, in Kelvin scale it's value is

If 6 g of solute dissolved in 100 g of water lowers the freezing point by 0.93 K. What is molar mass of solute? (K$$_\mathrm{f}$$ = 1.86 K kg mol$$^{-1}$$)

What is vapour pressure of a solution when $$2 \mathrm{~mol}$$ of a non-volatile solute are dissolved in $$20 \mathrm{~mol}$$ of water? $$\left(\mathrm{P}_1^0=32 \mathrm{~mm} \mathrm{Hg}\right)$$