Practice question

Given: The vapor pressure of pure water at 298 K is 23.8 mm Hg. What is the vapor pressure of a solution containing 18 g of sucrose ( C₁₂H₂₂O₁₁ ) in 162 g of water? (Molar mass: C₁₂H₂₂O₁₁ = 342 g/mol ) Formula: Moles of sucrose = 18/342 = 0.0526 mol. Substitution & Calculation: Moles of water = 162/18 = 9 mol . Mole fraction of water = 9/9 + 0.0526 = 0.994 . Vapor pressure = 0.994 × 23.8 = 23.66 mm Hg . Final Result: The computed value matches expected outcome and confirms correct choice as per latest NCERT 2026-27.