of a non-electrolyte solute dissolved in of benzene lowered the freezing point of benzene by . If th — Solutions and Colligative Properties Chemistry Question
Question
$1.00\text{ g}$ of a non-electrolyte solute dissolved in $50\text{ g}$ of benzene lowered the freezing point of benzene by $0.40\text{ K}$. If the $K_f$ of benzene is $5.12\text{ K kg mol}^{-1}$, calculate the experimental molar mass of the solute.
Answer: B
💡 Solution & Explanation
$\Delta T_f = K_f \times \frac{w_{solute} \times 1000}{M_{solute} \times W_{solvent}}$. Rearranging gives $M_{solute} = \frac{5.12 \times 1.00 \times 1000}{0.40 \times 50} = \frac{5120}{20} = 256\text{ g mol}^{-1}$.
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