1. Sodium chloride   KI   NaCl   CuO   AgBr   Hint Hint       2. Potassium iodide   ZnS   KOH   KCl   KI   Hint       3. Ferrous sulfide (Iron [II] sulfide)   NaOH   CuCl   KBr   FeS   Hint       4. Cuprous chloride (Copper [I] chloride)   CuCl   MgO   NaI   NaCl   Hint       5. Mercuric oxide (Mercury [II] oxide)   NaCl   ZnO   HgO   KI   Hint       6. Potassium bromide   AgCl   KOH   MgS   KBr   Hint       7. Sodium hydroxide   NaI   CuO   NaOH   AgBr   Hint