A solution of sucrose (molar mass $=342 \mathrm{~g} \mathrm{~mol}^{-1}$ ) has been prepared by disso

Question

A solution of sucrose (molar mass $=342 \mathrm{~g} \mathrm{~mol}^{-1}$ ) has been prepared by dissolving 68.5 g of sucrose in 1000 g of water. The freezing point of the solution obtained will be ( $K_{f}$ for water $=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$ )\

Professor PC Thomas Classes · Answer

(a): We know, $\Delta T_{f}=K_{f} m$ $$ m=\frac{w_{B}}{M_{B}} 	imes \frac{1000}{W_{A}}=\frac{68.5 	imes 1000}{342 	imes 1000}=\frac{68.5}{342} $$ $\Delta T_{f}=1.86 	imes \frac{68.5}{342}=0.372^{\circ} \mathrm{C}$\ $	herefore \quad T_{f}=0-0.372^{\circ} \mathrm{C}=-0.372^{\circ} \mathrm{C}$\