1. H2O2   copper sulfate   hydrogen peroxide   sodium hydroxide   hydrochloric acid   Hint Hint       2. SO2   calcium carbonate   sulfur dioxide   carbon dioxide   calcium sulfate   Hint       3. NaOH   sodium hydroxide   sulfur dioxide   sodium chloride   hydrogen peroxide   Hint       4. H2O   water   hydrochloric acid   magnesium oxide   ammonia   Hint       5. HCl   ammonia   carbon dioxide   hydrochloric acid   sodium carbonate   Hint       6. H2SO4   sulfuric acid   carbon dioxide   hydrochloric acid   water   Hint       7. NaCl   sodium chloride   hydrogen peroxide   ammonium sulfate   carbon disulfide   Hint