A solution has a mole ratio of pentane to hexane. The vapour pressures of the pure hydrocarbons at a — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

Mole fractions in liquid: $X_P = 1/5$, $X_H = 4/5$. Partial pressures: $p_P = 440 \times (1/5) = 88\text{ mm Hg}$; $p_H = 120 \times (4/5) = 96\text{ mm Hg}$. Total pressure $P = 88 + 96 = 184\text{ mm Hg}$. Mole fraction of pentane in vapour $Y_P = p_P / P = 88 / 184 \approx 0.478$.