1). HCl + NaOH = NaCl + H₂O
H⁺+Cl⁻ + Na⁺+OH⁻= Na⁺+Cl⁻ + H₂O
H⁺+OH⁻=H₂O
2). CuSO₄ + 2NaOH = Cu(OH)₂↓ + Na₂SO₄
Cu²⁺+SO₄²⁻ + 2Na⁺+2OH⁻ = Cu(OH)₂↓ + 2Na⁺+SO₄²⁻
Cu²⁺+2OH⁻= Cu(OH)₂↓
3). Na₂CO₃ + 2HCl = CO₂ + H₂O + 2NaCl
2Na⁺+CO₃²⁻ + 2H⁺+2Cl⁻ = CO₂ + H₂O + 2Na⁺+2Cl⁻
CO₃²⁻ + 2H⁺= CO₂ + H₂O