Predict whether the vapours will condense or not, at the given pressure? — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

The overall mole fractions in the vapour are $Y_A = 2.0 / 5.0 = 0.4$ and $Y_B = 3.0 / 5.0 = 0.6$. The dew point pressure (pressure at which the first drop of liquid forms) is $P = \frac{1}{(Y_A / P_A^\circ) + (Y_B / P_B^\circ)} = \frac{1}{(0.4 / 0.4) + (0.6 / 0.6)} = \frac{1}{1 + 1} = 0.5 \text{ bar}$. Since the given pressure (0.3 bar) is lower than the dew point pressure (0.5 bar), no condensation will occur. Therefore, correct answer is D.