The boiling point of a 2% (w/w) aqueous solution of a non-volatile, non-electrolyte solute is 0.102° — Solutions and Colligative Properties Chemistry Question
Question
The boiling point of a 2% (w/w) aqueous solution of a non-volatile, non-electrolyte solute is 0.102°C higher than that of pure water. If $K_b$ for water is $0.52 \text{ K-kg/mol}$, the molecular mass of the solute is
Answer: D
💡 Solution & Explanation
Elevation in boiling point $\Delta T_b = 0.102^\circ C$. A 2% (w/w) solution contains 2 g of solute in 98 g of water. Molality $m = (2/M) / 0.098$. Using $\Delta T_b = K_b \times m$, $0.102 = 0.52 \times [ (2/M) / 0.098 ] = (1.04) / (0.098 \times M)$. Solving for M: $M = 1.04 / (0.102 \times 0.098) = 1.04 / 0.009996 \approx 104$ g/mol. Therefore, correct answer is D.
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