Concept:The Common Ion Effect suppresses the solubility of a sparingly soluble salt when a highly soluble salt sharing one of the same ions is added to the solution.
Formula:$$ \text{KClO}_{3(s)} \rightleftharpoons \text{K}^+_{(aq)} + \text{ClO}^-_{3(aq)} $$
Solution:- When \( \text{KCl} \) is added, it completely dissociates into \( \text{K}^+ \) and \( \text{Cl}^- \).
- This floods the solution with \( \text{K}^+ \) ions.
- Because \( \text{K}^+ \) is an ion common to the \( \text{KClO}_3 \) equilibrium, Le Chatelier's Principle states the system will shift left to consume the excess \( \text{K}^+ \).
- This backward shift forces dissolved ions back into solid \( \text{KClO}_3 \), thereby decreasing its overall solubility.
Why other options are incorrect:Adding more solid \( \text{KClO}_3 \) to a saturated solution has no effect. Adding water (\( \text{H}_2\text{O} \)) dilutes the solution, allowing
more salt to dissolve (increasing absolute solubility).
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