Question

What will be the freezing point of $1\%$ solution of glucose in water, given that molal depression constant for water is $ 1.84\,K\, mol^{-1}$

• A. $272.898\, K$
• B. $0.102\,{}^{\circ}C $
• C. $273\, K$
• D. $108\,{}^{\circ}C $

Answer 1

Answer: (A)

Mass of solution $=100\, g$
Mass of glucose $=1\, g$
Mass of solvent $=100-1=99\, g$
$w =$ mass of solute glucose,
$W =$ mass of solvent $m =$ molar mass of solute
$\Delta T_{f} \times \frac{w}{m} \times \frac{1}{W / 1000}$
$=1.84 \times \frac{1}{180} \times \frac{1}{99 / 1000}=0.103$
Freezing point of the solution $=273-0.103$
$=272.897\, K$