1. 2Ni(OH)₂ + H₂SO₄ =(NiOH)₂SO₄ + 2H₂O
(NiOH)₂SO₄+ H₂SO₄ = 2NiSO₄ + 2H₂O
NiSO₄ + 2NaOH = Na₂SO₄ +Ni(OH)₂↓
2.
AICI₃ + 3NaOH = 3NaCI +AI(OH)₃↓
AI(OH)₃ + HCI= AI(OH)₂CI + H₂O
AI(OH)₂CI + 3HNO₃ = AI(NO₃)₃ + HCI↑+ 2H₂O
3.
Na₂S + H₂S = 2NaHS
4NaHS + 2HCI = Na₂S + 2NaCI +3H₂S↑
Na₂S + 2HCI = 2NaCI + H₂S↑