Question

If $0.1M$ solutions of $K_4\left[Fe{\left(CN\right)}_6\right]$ is prepared at $300K$ then its density$=1.2g/mL$. If solute is 50% dissociated, calculate $\Delta P$ of solution if $P$ of pure water $=25mm$ of $Hg$ ($K=39,Fe=56$)

Answer 1

density $=1,2g/mol$

weight of $1ml$ solution $=1.2g$

$1000ml$ solution $=1200g$

$1$ litre solution weight $1200g$

$\alpha =\frac{i-1}{m-1}$

$\alpha =0.5$ (given)

$K_4\left(Fe\right(CN{)}_6)\to 4K^{+}+[Fe(CN{)}_6{]}^{4-}$

$m=5$

$0.5=\frac{i-1}{5-1}i=3$

$\frac{\Delta P}{P^o}=i\times x_B$

$0.1M$ solution (given)

Moles of solute $=0.1$ in $1lt$ solution

Molecular Mass of solute $=368g$

Mass of solute $=36.8g$

Mass of soluent = Mass of solution -Mass of solute

$=1200-36.8$

$=1163.2g$

Mass of solvent $=\frac{1163.2}{18}=64.6222$

$x_B=\frac{0.1}{0.1+64.6222}$

$x_B=0.00154$

$P^o=25mm$ (given)

$\frac{\Delta P}{25}=3\times 0.00154$

Final Answer

$\Delta =0.11587mmofHg$