Practice question

Given: How many grams of a non-volatile solute (molar mass 180 g/mol) must be dissolved in 540 g of water to reduce its vapor pressure to 98% of its original value? These values define the system as per NCERT data. Formula: Relative lowering = p⁰ - p/p⁰ = 1 - 0.98 = 0.02. This is standard NCERT relation. Substitution & Calculation: Moles of water = 540/18 = 30 mol . 0.02 = n_2/30, n_2 = 0.6 mol . Mass = 0.6 × 180 = 108 g . Result: The computed value matches expected outcome and confirms correct choice as per NCERT.