Question

When mercuric iodide is added to an aqueous solution of potassium iodide the:

• A. freezing point is raised
• B. freezing point is lowered
• C. freezing point does not change
• D. boiling point does not change

Answer 1

Answer: (A)

freezing point is raised

$HgI$ reacts with $KI$, to form $K_2\left[Hg{I}_4\right]$. Due to this, the number of ions decreases thus decreasing the van't Hoff factor.

$\Delta T_f=i\times k_f\times m$

Since ${}^{\prime }{i}^{\prime }$ has decreased, it results in less depression in the freezing point causing the freezing point to rise.