A liquid solution is formed by mixing 10 moles of aniline and 20 moles of phenol at a temperature wh — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

Mole fraction of aniline $X_A = 10/30 = 1/3$. Mole fraction of phenol $X_B = 20/30 = 2/3$. Ideal vapour pressure $P_{total} = 90(1/3) + 87(2/3) = 30 + 58 = 88 \text{ mm Hg}$. Aniline and phenol form strong intermolecular hydrogen bonds with each other, resulting in a negative deviation from Raoult's law. The actual vapour pressure must be less than 88 mm Hg, which makes 82 mm Hg the only possible value. Therefore, correct answer is A.