Question

$31\, g$ of ethylene glycol $\left( C _{2} H _{6} O _{2}\right)$ is dissolved in $600\, g$ of water. The freezing point depression of the solution is $\left(K_{f}\right.$ for water is $1.86\, K\, kg\, mol ^{-1}$ )

• A. 0.77 K
• B. 1.55 K
• C. 4.65 K
• D. 3.10 K

Answer 1

Answer: (B)

$\because \Delta T_{f}=K_{f} \cdot \frac{W_{B}}{M_{B}} \times \frac{1000}{W_{A}}$

Given,

$W_{B}$ (mass of ethylene glycol) $=31\, g$

$W_{A}$ (mass of water) $=600\, g$

$K_{f}$ (for water) $=1.86\, K\, kg\, mol ^{-1}$

and $M_{B}\left(\right.$ for $\left.C _{2} H _{6} O _{2}\right)=62$

$\therefore \Delta T_{f}=\frac{1.86 \times 31 \times 1000}{62 \times 600}$

$=1.55\, K$