When 20 g of naphthoic acid () is dissolved in 50 g of benzene (), a freezing point depression of 2 — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

Molar mass of $\text{C}_{11}\text{H}_8\text{O}_2 = 11(12) + 8(1) + 2(16) = 132 + 8 + 32 = 172 \text{ g/mol}$. Molality $m = (20 / 172) / 0.050 \text{ kg} = 2.3256 \text{ m}$. $\Delta T_f = i \times K_f \times m \Rightarrow 2 = i \times 1.72 \times 2.3256 \Rightarrow 2 = i \times 4 \Rightarrow i = 0.5$. Therefore, correct answer is A.