In KI solution, mercuric iodide is added. The osmotic pressure of resultant solution will — Solutions and Colligative Properties Chemistry Question

💡 Solution & Explanation

Mercuric iodide ($\text{HgI}_2$) reacts with potassium iodide ($\text{KI}$) to form a complex ion: $2\text{KI} + \text{HgI}_2 \rightarrow \text{K}_2[\text{HgI}_4]$. Before the reaction, there are 4 ions per 2 KI molecules ($2\text{K}^+$ and $2\text{I}^-$). After the reaction, there are 3 ions ($2\text{K}^+$ and $1[\text{HgI}_4]^{2-}$). Since the total number of particles in solution decreases, the osmotic pressure decreases. Therefore, correct answer is B.