To determine which test will identify just one of the three solutions containing carbonate, sulphate, and sulphide ions, we need to analyze the reactions that occur when each of the given reagents is added to these solutions. ### Correct Option: C. Lead Nitrate Solution #### Explanation of Why Option C is Correct: 1. **Lead Nitrate and Sulphate Ions**: - When lead nitrate (Pb(NO₃)₂) is added to a solution containing sulphate ions (SO₄²⁻), a white precipitate of lead(II) sulphate (PbSO₄) forms. The reaction is as follows: \[ \text{Pb(NO}_3\text{)}_2 (aq) + \text{SO}_4^{2-} (aq) \rightarrow \text{PbSO}_4 (s) + 2\text{NO}_3^{-} (aq) \] - This precipitate is insoluble in water and can be used to confirm the presence of sulphate ions. 2. **Lead Nitrate and Carbonate Ions**: - If lead nitrate is added to a solution containing carbonate ions (CO₃²⁻), a different precipitate forms, which is lead(II) carbonate (PbCO₃): \[ \text{Pb(NO}_3\text{)}_2 (aq) + \text{CO}_3^{2-} (aq) \rightarrow \text{PbCO}_3 (s) + 2\text{NO}_3^{-} (aq) \] - However, this test does not exclusively identify sulphate ions, as it can also precipitate with carbonate ions. 3. **Lead Nitrate and Sulphide Ions**: - When lead nitrate is added to a solution containing sulphide ions (S²⁻), lead(II) sulphide (PbS) forms, which is also a black precipitate: \[ \text{Pb(NO}_3\text{)}_2 (aq) + \text{S}^{2-} (aq) \rightarrow \text{PbS} (s) + 2\text{NO}_3^{-} (aq) \] - This means that lead nitrate cannot uniquely identify sulphide ions either. Thus, while lead nitrate can precipitate with all three ions, it does not uniquely identify one of them. ### Why the Other Options are Wrong or Weaker: #### Option A: Barium Chloride Solution - **Barium Chloride and Sulphate Ions**: - Barium chloride (BaCl₂) will precipitate barium sulphate (BaSO₄) when added to a solution containing sulphate ions: \[ \text{BaCl}_2 (aq) + \text{SO}_4^{2-} (aq) \rightarrow \text{BaSO}_4 (s) + 2\text{Cl}^- (aq) \] - **Barium Chloride and Carbonate Ions**: - It will also precipitate barium carbonate (BaCO₃) with carbonate ions: \[ \text{BaCl}_2 (aq) + \text{CO}_3^{2-} (aq) \rightarrow \text{BaCO}_3 (s) + 2\text{Cl}^- (aq) \] - **Barium Chloride and Sulphide Ions**: - Barium sulphide (BaS) can also form with sulphide ions: \[ \text{BaCl}_2 (aq) + \text{S}^{2-} (aq) \rightarrow \text{BaS} (s) + 2\text{Cl}^- (aq) \] - **Conclusion**: Barium chloride cannot uniquely identify any of the ions. #### Option B: Dilute Hydrochloric Acid - **Hydrochloric Acid and Carbonate Ions**: - When dilute hydrochloric acid (HCl) is added to carbonate ions, carbon dioxide (CO₂) gas is released, which can be observed as effervescence: \[ \text{HCl} (aq) + \text{CO}_3^{2-} (aq) \rightarrow \text{H}_2\text{O} (l) + \text{CO}_2 (g) + 2\text{Cl}^- (aq) \] - **Hydrochloric Acid and Sulphate Ions**: - Sulphate ions do not react with hydrochloric acid in a way that produces a visible change. - **Hydrochloric Acid and Sulphide Ions**: - Sulphide ions will react with hydrochloric acid to produce hydrogen sulphide (H₂S), which has a characteristic rotten egg smell: \[ \text{HCl} (aq) + \text{S}^{2-} (aq) \rightarrow \text{H}_2\text{S} (g) + 2\text{Cl}^- (aq) \] - **Conclusion**: Hydrochloric acid can identify carbonate and sulphide ions, but not exclusively one. #### Option D: Calcium Chloride Solution - **Calcium Chloride and Carbonate Ions**: - Calcium chloride (CaCl₂) will precipitate calcium carbonate (CaCO₃) with carbonate ions: \[ \text{CaCl}_2 (aq) + \text{CO}_3^{2-} (aq) \rightarrow \text{CaCO}_3 (s) + 2\