1. Possible cations responsible for green color in solutions: Fe2+, Cr3+, Cu2+. 2. Formula of the green precipitate from solution A: Fe(OH)2. 3. Formula of the species responsible for dark green color in solution C: [Fe(OH)4]2−. 4. Type of reaction turning dark green solution to yellow: Oxidation. 5. Ion responsible for final orange color after adding ethanoic acid: Fe3+. 6. Control measure to reduce risk when using pure ethanoic acid: Use of a fume cupboard and personal protective equipment.