The vapour pressures of two liquids P and Q are 80 and 60 torr respectively. The total vapour pressure of solution obtained by mixing 3 moles of P and 2 moles of Q would be: 

A set of solutions is prepared using 180 g of water as a solvent and 10 g of different non-volatile solutes A, B and C. What is the correct order of relative lowering of vapour pressure in the presence of these solutes?
[Given: Molar mass of A = 100 g ${\mathrm{mol}}^{-1}$; B = 200 g ${\mathrm{mol}}^{-1}$; C = 10,000 g ${\mathrm{mol}}^{-1}$]

At room temperature, a dilute solution of urea is prepared by dissolving 0.60 g of urea in 360 g of water. If the vapour pressure of pure water at this temperature is 35 mm Hg, then calculate the lowering of vapour pressure:
(Given: Molar mass of urea = 60 g mol^–1)