№1.
Cu(NO₃)₂ → Cu → x → Cu(OH)₂
1) 3Cu(NO₃)₂ + 2Al = 2Al(NO₃)₃ + 3Cu↓
2) Cu + 2H₂SO₄ = CuSO₄ + H₂O + SO₂↑ (X)
3) CuSO₄ + 2NaOH = Na₂SO₄ + Cu(OH)₂↓
Cu²⁺+ SO₄²⁻ + 2Na⁺ + 2OH⁻ = 2Na⁺ + SO₄²⁻ + Cu(OH)₂↓
Cu²⁺+ 2OH⁻ = Cu(OH)₂↓
№2.
Si → SiO₂ → Na₂SiO₃ (+HNO₃) → x
1) Si + O₂ = SiO₂
2) SiO₂ + 2NaOH = Na₂SiO₃ + H₂O
3) Na₂SiO₃ + 2HNO₃ = H₂SiO₃↓ + 2NaNO₃ (X)
2Na⁺ + SiO₃²⁻ + 2H⁺ + 2NO₃⁻ = H₂SiO₃↓ + 2Na⁺ + 2NO₃⁻
2H⁺ + SiO₃²⁻ = H₂SiO₃↓
№3.
Fe₂O₃ (+H₂) → x → FeCl₂ → Fe(OH)₂
1) Fe₂O₃ +3H₂ → 2Fe+3H₂O (X)
2) Fe + 2HCl = FeCl₂ + H₂↑
Fe³⁺ + 2H⁺ + 2Cl⁻ = FeCl₂ + 2H⁺
Fe³⁺ + 2Cl⁻ = FeCl₂
3) FeCl₂ + 2KOH = 2KCl + Fe(OH)₂↓