1. Hydrochloric acid (Hydrogen chloride)   HCl   FeS   NaOH   NaI   Hint Hint       2. Argentous bromide (Silver [I] bromide)   ZnS   CuO   KOH   AgBr   Hint       3. Potassium iodide   CuCl   KI   NaI   MgO   Hint       4. Sodium hydroxide   CuCl   NaOH   NaI   FeS   Hint       5. Plumbous oxide (Lead [II] oxide)   ZnO   PbO   NaOH   KOH   Hint       6. Mercuric oxide (Mercury [II] oxide)   PbO   HgO   KI   NaOH   Hint       7. Potassium bromide   KCl   HCl   NaI   KBr   Hint