Question

The freezing point of a 5% by mass $C{H}_{3}COOH(aq.)$ solution is $-{1.576}^{o}C$. The van't Hoff factor is: $(K_f$ of water $=1.86Kmo{l}^{-1}kg)$

• A. $0.996$
• B. $2$
• C. $0.5$
• D. $1.016$

Answer 1

The correct option is D $1.016$

The van't Hoff factor is $1.016$
$\Delta T_f=\frac{1000\times K_f\times w}{m\times W}$

$=\frac{1000\times 1.86\times 5}{60\times 100}$

$=1.55$

$i=\frac{\Delta T_{f_{exp}}}{\Delta T_{f_{eal}}}=\frac{1.576}{1.55}=1.016$
Thus the value of i is greater than $1$ so acetic acid ionises in water.