Pb(NO₃)₂ + 2KI = 2KNO₃ + PbI₂↓
Pb²⁺+ 2NO₃⁻ + 2K⁺ + 2I⁻ = 2K⁺ + NO₃⁻ + PbI₂↓
Pb²⁺ + 2I⁻ =  PbI₂↓

NiCl₂ + H₂S =  2HCl + NiS↓
Ni²⁺ + 2Cl + 2H⁺ + S²⁻ =  2H⁺ + 2Cl⁻ + NiS↓
Ni²⁺  + S²⁻ =  NiS↓

K₂CO₃ + 2HCl = 2KCl + CO₂↑ + H₂O
2K⁺ + CO₃²⁻ + 2H⁺ + 2Cl⁻ = 2K⁺ + 2Cl⁻ + CO₂↑ + H₂O
 CO₃²⁻ + 2H⁺  =  CO₂↑ + H₂O

CuSO₄ +2NaOH = Na₂SO₄ +Cu(OH)₂↓
Cu²⁺ + SO₄²⁺ + 2Na⁺ + 2OH⁻ = 2Na⁺ + SO₄²⁻ +Cu(OH)₂↓
Cu²⁺  + 2OH⁻ = Cu(OH)₂↓