Question

$45\, g$ of ethylene glycol $\left(C_{2} H_{6} O_{2}\right)$ is mixed with $600\, g$ of water, what is the depression of freezing point?

• A. $7.9\, K$
• B. $2.5\, K$
• C. $6.6\, K$
• D. $2.2\, K$

Answer 1

Answer: (D)

$2.2\, K$

Answer 2

Depression of freezing point is given as
$\Delta T_{f}=\frac{K_{f} \times w \times 1000}{m \times W}$ For water $K_{f}=1.86\, g\,mol ^{-1}$
$w=45\, g$
$W=600\, g$
$m\left(C_{2} H_{6} O_{2}\right)$
$=2 \times 12+6 \times 1+2 \times 16=62$
$\therefore \Delta T_{f-}=\frac{1.86 \times 45 \times 1000}{62 \times 600}=2.25 \,K$