Question

$30mL$ of $0.1MKI(aq)$ and $10mL$ of $0.2MAgN{O}_3$ are mixed. The solution is then filtered out. Assuming no change in total volume, depression in freezing point of the resulting solution will be $y\times 10^{-2}{}^{\circ }C$. Value of $y$ : (Given: $K_f$ for $H_{2}O=1.86Kkgmol{m}^{-1}$, assume molarity = molality)

Answer 1

Answer: 28

$\therefore$ [KI] in solution $=\frac{1}{40}$ and [KNO₃] $=\frac{2}{40}$ &
(Assuming molarity = molality for dilute soluation)
$\therefore \text{Δ}{\left(\text{T}\right)}_{\text{f}}=\text{Δ}{\left(\text{T}\right)}_{\text{f}}(\text{b}\text{y}\text{K}\text{I})+\text{Δ}{\left(\text{T}\right)}_{\text{f}}(\text{b}\text{y}\text{K}\text{N}{\left(\text{O}\right)}_3)$
$=\text{molality}\times \text{1.86}\times {\text{i}}_{\text{KI}}+\text{molality}\times \text{1.86}\times {\text{i}}_{{\text{KNO}}_3}$
$=(\frac{1}{40}\times 1.86\times 2)+(\frac{2}{40}\times 1.86\times 2)$
$=0\text{.}093+0\text{.}186=0\text{.}279=0.28^{\circ }\text{C}$