viii. Solubility of a sparingly soluble salt get affected in presence of a soluble salt having one common ion. Explain.

4. Answer the following :

viii. Solubility of a sparingly soluble salt get affected in presence of a soluble salt having one common ion. Explain.

Answer:-

i. The presence of a common ion has an impact on the solubility of sparingly soluble salts.

ii. Consider the solubility equilibrium of AgCl,

\[\ce{AgCl_{(s)} ⇌ Ag^+_{(aq)} + Cl^-_{(aq)}}\]

The solubility product of AgCl is given by

Ksp = [Ag+][Cl-]

iii. Let's introduce AgNO3 into the saturated solution of AgCl. AgNO3, being a strong electrolyte, completely dissociates in the solution:

\[\ce{AgNO_{3(aq)} ⇌ Ag^+_{(aq)} + NO_3^-_{(aq)}}\]

iv. The dissociation of both AgCl and AgNO3 leads to the presence of a common Ag+ ion. The concentration of Ag+ ions in the solution increases due to the complete dissociation of AgNO3.

v. Following Le-Chatelier's principle, the addition of Ag+ ions from AgNO3 to the AgCl solution shifts the solubility equilibrium of AgCl to the left. The reverse reaction, where AgCl precipitates, becomes favored until the solubility equilibrium is re-established.

vi. However, the value of Ksp remains constant since it represents an equilibrium constant. Consequently, the solubility of sparingly soluble compounds decreases in the presence of a common ion in the solution.