Safrole is contained in oil of sassafras and was once used to flavour root beer. A 2.4 mg sample of — Solutions and Colligative Properties Chemistry Question
Question
Safrole is contained in oil of sassafras and was once used to flavour root beer. A 2.4 mg sample of safrole was dissolved in 100.0 mg of diphenyl ether. The solution had a freezing of $25.64^\circ\text{C}$. The freezing point of pure diphenyl ether is $26.84^\circ\text{C}$, and the freezing-point-depression constant, $K_f$, is $8.00^\circ\text{C/m}$. The molecular mass of safrole is
💡 Solution & Explanation
The freezing point depression is $\Delta T_f = 26.84 - 25.64 = 1.20^\circ\text{C}$. Mass of safrole $w = 2.4 \text{ mg} = 2.4 \times 10^{-3} \text{ g}$. Mass of solvent $W = 100.0 \text{ mg} = 0.1 \text{ g} = 10^{-4} \text{ kg}$. Using $M = (K_f \times w) / (\Delta T_f \times W_{kg}) = (8.00 \times 2.4 \times 10^{-3}) / (1.20 \times 10^{-4}) = 19.2 \times 10^{-3} / 1.2 \times 10^{-4} = 16 \times 10^1 = 160 \text{ g/mol}$. Therefore, correct answer is 0160.