Question

When an excess of $AgN{O}_3$ is treated with $KI$ solution, $AgI$ forms a:

• A. positively charged sol
• B. negatively charged sol
• C. neutral sol
• D. true solution

Answer 1

The correct option is A positively charged sol

On treatment of $AgN{O}_3$ with $KI$ solution, $AgI$ is formed.
${\mathrm{AgNO}}_3+\mathrm{KI}\to \mathrm{AgI}+{\mathrm{KNO}}_3$
As an excess of $AgN{O}_3$ is taken, it also exists in its dissociated form as follows,
${\mathrm{AgNO}}_3\to {\mathrm{Ag}}^{+}+{{\mathrm{NO}}_3}^{-}$
These $A{g}^{+}$ ions are adsorbed on $AgI$ and $\left[AgI\right]A{g}^{+}$ are formed. Thus, the colloidal particles acquire a positive charge.