3Na₂S + 2Fe(NO₃)₃ = 6NaNO₃ + Fe₂S₃↓;
6Na⁺ + 3S²⁻ + 2Fe³⁺ + 6NO₃⁻ = 6Na⁺ + 6NO₃⁻ + Fe₂S₃↓;
3S²⁻ + 2Fe³⁺ = Fe₂S₃↓.
CuSO₄ + H₂S = CuS + H₂SO₄;
Cu²⁺ + SO₄²⁻ + H₂S = CuS + 2H⁺ + SO₄²⁻;
Cu²⁺ + H₂S = CuS + 2H⁺.
CaCl₂ + H₂CO₃ = CaCO₃↓ + 2HCl;
Ca²⁺ + 2Cl⁻ + 2H⁺ + CO₃²⁻ = CaCO₃↓ + 2H⁺ + 2Cl⁻;
Ca²⁺ + CO₃⁻ = CaCO₃↓.