Appeared in: 2025 (2 sets)
Vapour pressure of pure water at $298\text{ K}$ is $24\cdot8\text{ mm Hg}$. Calculate the lowering in vapour pressure of an aqueous solution which freezes at $-0\cdot3^{\circ}\text{C}$. ($K_f$ of water $= 1\cdot86\text{ K kg mol}^{-1}$)