2Na + O₂ = Na₂O₂
Na₂O₂ + 2Na =2Na₂O
Na₂O + H₂O = 2NaOH
NaOH + H₂S = Na₂S + H₂O
Na₂S + ZnBr₂ = ZnS + 2NaBr
2Na⁺ + S²⁻ + Zn²⁺ + 2Br⁻ = ZnS + 2Na⁺ + 2Br⁻
S²⁻ + Zn²⁺ = ZnS
2Ba + O₂ = 2BaO
BaO + 2HNO₂ = Ba(NO₂)₂ + H₂O
Ba(NO₂)₂ + K₂SO₄ = BaSO₄ + 2KNO₂
Ba²⁺ + 2NO₂⁻ + 2K⁺ + SO₄²⁻ = BaSO₄ + 2K⁺ + 2NO₂⁻
Ba²⁺ + SO₄²⁻ = BaSO₄
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