The vapour pressure of solution at this composition is — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

Total pressure $P = P_B^\circ + (P_A^\circ - P_B^\circ) X_A$. Substituting $X_A = \frac{\sqrt{P_A^\circ \cdot P_B^\circ} - P_B^\circ}{P_A^\circ - P_B^\circ}$ into this equation gives $P = P_B^\circ + (\sqrt{P_A^\circ \cdot P_B^\circ} - P_B^\circ) = \sqrt{P_A^\circ \cdot P_B^\circ}$. Therefore, correct answer is A.