What is the composition of first drop of liquid formed? — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

The composition of the first drop of liquid is in equilibrium with the bulk vapour. Using Raoult's law, $X_A = \frac{Y_A \cdot P_{\text{total}}}{P_A^\circ} = \frac{0.4 \times 0.5}{0.4} = 0.5$. Therefore, correct answer is B.