13 g nonvolatile solute dissolved in 100 gm of water gives vapour pressure of 27.371 mm Hg at room temperature. Find the molar mass of solute. (vapour pressure of water is 28.065 mm Hg at room temperature)

Step-by-step solution

Given: Mass of solute, w₂ = 13 g Mass of solvent (water), w₁ = 100 g Vapour pressure of pure water, P^0 = 28.065 mm Hg Vapour pressure of solution, P_s = 27.371 mm Hg Molar mass of water, M₁ = 18 g/mol Using the formula for relative lowering of vapour pressure (assuming dilute solution): P^0 - P_s P^0 = n₂ n₁ P^0 - P_s P^0 = w₂ M₁ M₂ w₁ M₂ = w₂ M₁ P^0 w₁ (P^0 - P_s) Substituting the given values: M₂ = 13 18 28.065 100 (28.065 - 27.371) M₂ = 13 18 28.065 100 0.694 M₂ 94.74 g/mol Answer: 94.74 g/mol