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 #### Step-by-Step Explanation: 1. **Understanding the Ions**: - **Carbonate ions (CO₃²⁻)**: React with acids to produce carbon dioxide gas (CO₂), which can be observed as effervescence. - **Sulfate ions (SO₄²⁻)**: React with barium ions (from barium chloride) to form a white precipitate of barium sulfate (BaSO₄). - **Sulfide ions (S²⁻)**: React with lead ions (from lead nitrate) to form a black precipitate of lead sulfide (PbS). 2. **Reactions with Lead Nitrate**: - When lead nitrate (Pb(NO₃)₂) is added to a solution containing sulfide ions (S²⁻), a black precipitate of lead sulfide (PbS) forms: \[ \text{Pb}^{2+} + \text{S}^{2-} \rightarrow \text{PbS (s)} \text{ (black precipitate)} \] - This reaction is specific to sulfide ions, as neither carbonate nor sulfate ions will produce a precipitate with lead nitrate. 3. **Why Other Options Are Incorrect**: - **A. Barium Chloride Solution**: - Barium chloride (BaCl₂) will react with sulfate ions to form a white precipitate of barium sulfate (BaSO₄): \[ \text{Ba}^{2+} + \text{SO₄}^{2-} \rightarrow \text{BaSO₄ (s)} \text{ (white precipitate)} \] - It will not identify sulfide or carbonate ions specifically, as carbonate ions will not precipitate with barium ions. - **B. Dilute Hydrochloric Acid**: - When dilute hydrochloric acid (HCl) is added to a carbonate solution, it reacts to produce carbon dioxide gas: \[ \text{CO₃}^{2-} + 2\text{HCl} \rightarrow \text{CO₂ (g)} + \text{H₂O} + 2\text{Cl}^- \] - However, it will also react with sulfide ions to produce hydrogen sulfide gas (H₂S), which is also a gas and can be confused with the effervescence from carbonates. Therefore, it does not uniquely identify one ion. - **D. Calcium Chloride Solution**: - Calcium chloride (CaCl₂) can react with sulfate ions to form a precipitate of calcium sulfate (CaSO₄) under certain conditions, but it does not react specifically with sulfide or carbonate ions. Thus, it does not uniquely identify any of the ions. ### Summary of Key Points: - **Lead Nitrate** specifically identifies sulfide ions by forming a black precipitate of lead sulfide (PbS). - **Barium Chloride** identifies sulfate ions but does not distinguish them from sulfide or carbonate ions. - **Dilute Hydrochloric Acid** can react with both carbonate and sulfide ions, leading to confusion. - **Calcium Chloride** does not provide a clear identification of any of the ions. ### Revision Summary: - Lead nitrate solution uniquely identifies sulfide ions by forming a black precipitate (PbS). - Barium chloride identifies sulfate ions but not sulfide or carbonate. - Dilute hydrochloric acid reacts with both carbonate and sulfide, causing confusion. - Calcium chloride does not distinctly identify any of the ions present.