Question

What should be the freezing point of aqueous solution containing $17\,g$ of $C_{2}H_{5}OH$ in $1000\,g$ of water $(K_{f}$ for water $=1.86\,deg\,kg\, mol^{-1})$ ?

• A. $-0.69^{\circ}C$
• B. $0.34^{\circ}C$
• C. $0.0^{\circ}C$
• D. $-0.34^{\circ}C$

Answer 1

Answer: (A)

$\Delta T=K_{f} \times\frac{w_{B}\times1000}{m_{B}\times w_{A}}$
$=1.86\times\frac{17\times1000}{46\times1000}=0.69$
$\therefore $ Freezing point of solution $=0-0.69=-0.69^{\circ}C$