Question:

When a dilute \(AgNO_3\) solution is mixed with excess of dilute \(KI\), the colloidal solution formed is

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In precipitate sols, the ion present in excess is preferentially adsorbed on the colloidal particles and determines the charge on the sol.
Updated On: Jun 18, 2026
  • \(AgNO_3/I^-\)
  • \(AgI\)
  • \(AgI/Ag^+\)
  • \(AgI/I^-\)
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The Correct Option is D

Solution and Explanation

Step 1: Write the precipitation reaction.
When silver nitrate reacts with potassium iodide, \[ AgNO_3 + KI \rightarrow AgI \downarrow + KNO_3 \] A precipitate of silver iodide is formed.

Step 2: Consider the reagent present in excess.

The question states that \(KI\) is present in excess.
Therefore, after precipitation, iodide ions remain in solution.

Step 3: Determine the charge on colloidal particles.

According to the preferential adsorption theory, the ion present in excess gets adsorbed on the surface of the precipitate.
Since \(I^-\) ions are present in excess, they are adsorbed on the surface of \(AgI\) particles.
Thus, the colloidal particles become negatively charged.
The colloidal sol is represented as \[ AgI/I^- \]

Step 4: Final conclusion.

Hence, the colloidal solution formed is \[ \boxed{AgI/I^-} \] Therefore, the correct option is (4).
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