Question

The freezing point (in ${}^{\circ }C$) of a solution containing 0.1 g of $K_3\left[Fe\right(CN{)}_6\left]\right(molwt=329)$ in 100 g of water $(kf=1.86Kkg/mol)$ is

• A. $-2.3\times {10}^{-2}$
• B. $-5.7\times {10}^{-2}$
• C. $-5.7\times {10}^{-3}$
• D. $-1.2\times {10}^{-2}$

Answer 1

The correct option is A $-2.3\times {10}^{-2}$

$K_3\left[Fe\right(CN{)}_6]\rightleftharpoons 3K^{+}+[Fe(CN{)}_6{]}^{3-}$
$i=4$
$\Delta Tf=\frac{i\times kf\times 1000\times w_2}{W_1\times M_2}=\frac{4\times 1.86\times 1000\times 0.1}{100\times 329}$
$f.pt=0-2.3\times {10}^{-2}$
$=-2.3\times {10}^{-2}C$