а). Fe → FeCl₂ → Fe(OH)₂ → Fe(OH)₃ → Fe(NO₃)₃.
1. Fe + 2HCl = FeCl₂ + H₂↑.
2. FeCl₂ + 2KOH = Fe(OH)₂↓ + 2KCl.
3. 4Fe(OH)₂ + 2H₂O + O₂ = 4Fe(OH)₃↓.
4. Fe(OH)₃ + HNO₃ = Fe(NO₃)₃ + 2H₂O.
б). Al → Al₂(SO₄)₃ → Al(OH)₃ → NaAlO₂.
1. 2Al + 3H₂SO₄ = Al₂(SO₄)₃ + 3H₂↑.
2. Al₂(SO₄)₃ + 6KOH = 2Al(OH)₃↓ + 3K₂SO₄.
3. Al(OH)₃ + NaOH = NaAlO₂ + 2H₂O.