Concept:The addition of an ion that is already present in an equilibrium mixture of a sparingly soluble salt shifts the equilibrium toward solid precipitation.
Formula:$$ \text{AgCl}_{(s)} \rightleftharpoons \text{Ag}^+_{(aq)} + \text{Cl}^-_{(aq)} $$
Solution:- \( \text{NaCl} \) is a strong electrolyte and dissociates completely into \( \text{Na}^+ \) and \( \text{Cl}^- \) ions.
- This significantly increases the concentration of \( \text{Cl}^- \) ions in the solution.
- According to Le Chatelier's Principle, the equilibrium shifts backwards to consume the excess \( \text{Cl}^- \).
- This results in the precipitation of more solid \( \text{AgCl} \), a phenomenon known as the common ion effect.
Why other options are incorrect:Solubility generally describes the ability to dissolve, not precipitate. The term 'unsaturation' would imply more could dissolve, opposite to precipitation.
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