а). Cl₂ → HCl → CaCl₂ → CaCO₃.
Cl₂ + H₂ = 2HCl;
2HCl + Ca = CaCl₂ + H₂↑;
CaCl₂ + H₂CO₃ = CaCO₃ + 2HCl.
б). Li → Li₂O → LiCl → LiNO₃.
4Li + O₂ = 2Li₂O;
Li₂O + 2HCl = 2LiCl + H₂O↑;
LiCl + HNO₃ = LiNO₃ + HCl.
в). Ba → BaO → Ba(OH)₂ → BaCl₂ → BaSO₄.
2Ba + O₂ = 2BaO;
BaO + H₂O = Ba(OH)₂;
Ba(OH)₂ + 2HCl = BaCl₂ + 2H₂O;
BaCl₂ + H₂SO₄ = BaSO₄ + 2HCl.