Question

If a dilute solution of NaI is added to dilute solution of excess $AgNO_3$, then species adsorbed on AgI colloidal particles is

• A. $Na^+$
• B. $Ag^+$
• C. $I^-$
• D. $NO_3^-$

Hint:

In colloids formed by double decomposition, the ion present in excess gets adsorbed on the colloidal particles.

Answer 1

The Correct Option is B

Step 1: Formation of AgI sol.
When a dilute solution of NaI is added to excess $AgNO_3$, silver iodide sol is formed according to the reaction:
\[ Ag^+ + I^- \rightarrow AgI(\text{sol}) \]
Step 2: Identify the excess ion.
Since $AgNO_3$ is present in excess, $Ag^+$ ions remain in excess in the solution.
Step 3: Adsorption of ions.
The colloidal AgI particles preferentially adsorb the ions present in excess, thereby acquiring the same charge.
Step 4: Conclusion.
Hence, $Ag^+$ ions are adsorbed on AgI colloidal particles.