Question

$100\text{mL}$ each of two sols of $AgI$, one obtained by adding $AgN{O}_3$ to slight excess of $KI$ and another obtained by adding $KI$ to a slight excess of $AgN{O}_3$, are mixed together. Then

• A. A true solution will be obtained
• B. The two sols will stabilize each other
• C. The sol particles will acquire more electric charge
• D. The sols will coagulate each other mutually

Answer 1

The correct option is D The sols will coagulate each other mutually

$\underset{\left(excess\right)}{KI}+AgN{O}_3\to AgI+KN{O}_3$
$AgI+I^{–}\to \left[AgI\right]I^{–}\text{(Negatively charge sol)}$
$KI+\underset{\left(excess\right)}{AgN{O}_3}\to AgI+KN{O}_3$
$AgI+A{g}^{+}\to \left[AgI\right]A{g}^{+}\text{Positively charged sol}$

The sols obtained in two cases are oppositely charged, thus they coagulate each other mutually.
Therefore, the correct answer is (C).