1. Solid Calcium is burned in Oxygen to produce Calcium Oxide Is it 2Ca (s) + O2 (g) -> CaO (aq) ?
2. Aqueous solutions of barium hydroxide and potassium sulfate are mixed to produce barium sulfate and potassium hydroxide
3. Iron + Oxygen -> Iron (III) Oxide (note: not aqueous!)
4. Sulfuric acid is mixed with aqueous sodium hydroxide to produce water and sodium sulfate.
5. Liquid C6H12 is burned in air.