Chemistry - Liquid Solution Question with Solution | TestHub

When mercuric iodide is added to the aqueous solution of potassium iodide the freezing point is raised as$\mathrm{\Delta }{\mathrm{T}}_{\mathrm{f}}$decreases due to complex formation number of species decrease and molecular weight increases.
${\text{ΔT}}_{\text{f}}\propto \frac{1}{\text{Molecular}\text{weight}}\propto$number of species
$\mathrm{H}\mathrm{g}{\mathrm{I}}_2$although insoluble in water but shows complex formation with KI as
$\text{2KI}\text{+}{\text{HgI}}_{\text{2}}\to {\text{K}}_{\text{2}}\left[{\text{HgI}}_{\text{4}}\right]$
$\text{2KI}\to {\text{2K}}^{\text{+}}{\text{+2I}}^{-}\text{(4}\text{ions)}$
${\text{K}}_{\text{2}}\left[{\text{HgI}}_{\text{4}}\right]\to {\text{2K}}^{\text{+}}{\left[{\text{HgI}}_{\text{4}}\right]}^{-\text{2}}\text{(3}\text{ions)}$
Here number of species decreases due to the reaction. Hence,${\text{ΔT}}_{\text{f}}\downarrow$and${\text{T}}_{\text{f}}\uparrow$