question_answer 30)

Calculate the mass of a non-volatile solute (molecular mass 40 g mol–1) which should be dissolved in 114 g octane to reduce its vapour pressure to 80%.

Answer:

ps = 80% of p° = 0.80p° No. of moles octane (solvent). [Molar mass of octane, C8 H18 = 114 g mol?1g] nB = 0.2 mol wB = (0.2 mol) × (40g mol?1) = 8.0 g.