Question

When dilute aqueous solution of $AgNO_{3}$ (excess) is added to $KI$ solution, positively charged sol of $AgI$ is formed due to adsorption of

• A. $ NO_{3}^{-} $
• B. $ O_{2}^{-} $
• C. $ Ag^{+}$
• D. $K^{+}$

Answer 1

Answer: (C)

Colloidal particles are either positively charged or negatively charged. This charge is due to preferential adsorption of either positive or negative ions on their surface. There is adsorption of common ion present in excess.
When aqueous solution of $AgNO _{3}$ is added to KI solution, positively charged sol of AgI is obtained due to the adsorption of $Ag ^{+}$ions on AgI molecules.
$\underset{\text { excess }}{ AgNO _{3}+ KI } \longrightarrow AgI + KNO _{3}$
$AgI +AgNO_3 \longrightarrow \underset{\text{fixed part positive sol}}{[AgI] Ag^+} :\underset{\text{diffused part}}{NO^-_{3}}$