To determine which pair of compounds would form a precipitate when their aqueous solutions are mixed, we need to consider the solubility rules for ionic compounds in water. A precipitate forms when two soluble ionic compounds react to form an insoluble compound. ### Analyzing Each Option **Option A: NaCl and KNO\(_{3}\)** - **Ionic Components**: Na\(^+\), Cl\(^-\), K\(^+\), NO\(_{3}^-\) - **Possible Products**: NaNO\(_{3}\) and KCl - **Solubility**: Both NaNO\(_{3}\) and KCl are soluble in water. Therefore, no precipitate forms. **Option B: KCl and NaNO\(_{3}\)** - **Ionic Components**: K\(^+\), Cl\(^-\), Na\(^+\), NO\(_{3}^-\) - **Possible Products**: KNO\(_{3}\) and NaCl - **Solubility**: Both KNO\(_{3}\) and NaCl are soluble in water. Therefore, no precipitate forms. **Option C: K\(_{2}\)SO\(_{4}\) and BaCl\(_{2}\)** - **Ionic Components**: K\(^+\), SO\(_{4}^{2-}\), Ba\(^{2+}\), Cl\(^-\) - **Possible Products**: BaSO\(_{4}\) and KCl - **Solubility**: BaSO\(_{4}\) is insoluble in water (according to solubility rules), while KCl is soluble. Therefore, when these two solutions are mixed, BaSO\(_{4}\) will precipitate out of the solution. **Option D: NH\(_{4}\)NO\(_{3}\) and CO\(_{3}^{2-}\)** - **Ionic Components**: NH\(_{4}^+\), NO\(_{3}^-\), CO\(_{3}^{2-}\) - **Possible Products**: NH\(_{4}\)CO\(_{3}\) and NO\(_{3}^-\) - **Solubility**: Ammonium carbonate (NH\(_{4}\)CO\(_{3}\)) is soluble in water. Therefore, no precipitate forms. ### Conclusion The correct answer is **C: K\(_{2}\)SO\(_{4}\) and BaCl\(_{2}\)** because it leads to the formation of BaSO\(_{4}\), which is insoluble and thus precipitates out of the solution. ### Why Other Options Are Incorrect - **Option A**: Both products are soluble, so no precipitate forms. - **Option B**: Both products are soluble, so no precipitate forms. - **Option D**: The product formed is soluble, so no precipitate forms. ### Summary of Key Points - A precipitate forms when two soluble ionic compounds react to form an insoluble compound. - BaSO\(_{4}\) is a well-known insoluble compound, leading to the formation of a precipitate in option C. - Always refer to solubility rules to determine if a precipitate will form when mixing solutions. - The other options resulted in soluble products, hence no precipitate was formed. This thorough understanding of solubility rules and the behavior of ionic compounds in solution is crucial for predicting the outcomes of chemical reactions in aqueous environments.