Question:medium

The solubility product of AgI at 25ºC is 1.0×10–16 mol2L–2. The solubility of AgI in 10–4N solution of KI at 25ºC is approximately (in mol L–1):

Updated On: Apr 28, 2026
  • 1.0×10–16
  • 1.0×10–12
  • 1.0×10–10
  • 1.0×10–8
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The Correct Option is B

Solution and Explanation

To find the solubility of AgI in a 10–4 N solution of KI, we need to consider the common ion effect. AgI is a sparingly soluble salt, and its solubility is reduced in the presence of a common ion (I from KI).

The solubility equilibrium for AgI is:

\[ \text{AgI (s)} \leftrightarrow \text{Ag}^+ (aq) + \text{I}^- (aq) \]

The solubility product (Ksp) of AgI is given as 1.0×10–16 mol2L–2. In an unsaturated or saturated solution of AgI, Ksp is expressed as:

\[ K_{sp} = [\text{Ag}^+][\text{I}^-] \]

Let S be the solubility of AgI in mol L–1 in the KI solution. In this solution, the concentration of I ions originally provided by KI is 10-4 mol L–1, and S is very small compared to 10-4. Therefore, the total concentration of I can be approximated as 10-4 mol L–1.

Substitute the concentrations into the Ksp expression:

\[ K_{sp} = [\text{Ag}^+][\text{I}^-] = S \times 10^{-4} \]

Setting up the equation with Ksp:

\[ 1.0 \times 10^{-16} = S \times 10^{-4} \]

Solving for S:

\[ S = \frac{1.0 \times 10^{-16}}{10^{-4}} = 1.0 \times 10^{-12} \]

Thus, the solubility of AgI in a 10-4N solution of KI is approximately 1.0 × 10-12 mol L-1.

Therefore, the correct answer is 1.0 × 10-12.

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