1) hydrochloric acid with nickel:
Balanced molecular equation: Ni(s) + 2HCl(aq) → NiCl₂(aq) + H₂(g).
Ionic equation: Ni(s) + 2H⁺(aq) + 2Cl⁻(aq) → Ni²⁺(aq) + 2Cl⁻(aq) + H₂(g).
Net ionic equation: Ni(s) + 2H⁺(aq) → Ni²⁺(aq) + H₂(g).
Nickel is oxidized from oxidation number 0 (Ni) to oxidation number +2, hydrogen is reduced from oxidation number +1 to oxidation number 0 (H₂).
2) sulfuric acid with iron:
Balanced molecular equation: Fe(s) + H₂SO₄(aq) → FeSO₄(aq) + H₂(g).
Ionic equation: Fe(s) + 2H⁺(aq) + SO₄²⁻(aq) → Fe²⁺(aq) + SO₄²⁻(aq) + H₂(g).
Net ionic equation: Fe(s) + 2H⁺(aq) → Fe²⁺(aq) + H₂.
Iron is oxidized from oxidation number 0 (Fe) to oxidation number +2, hydrogen is reduced from oxidation number +1 to oxidation number 0 (H₂).
3) hydrobromic acid with magnesium :
Balanced molecular equation: Mg(s) + 2HBr(aq) → MgBr₂(aq) + H₂(g).
Ionic equation: Mg(s) + 2H⁺(aq) + 2Br⁻(aq) → Mg²⁺(aq) + 2Br⁻(aq) + H₂(g).
Net ionic equation: Mg(s) + 2H⁺(aq) → Mg²⁺(aq) + H₂(g).
Magnesium is oxidized from oxidation number 0 (Mg) to oxidation number +2, hydrogen is reduced from oxidation number +1 to oxidation number 0 (H₂).
4) acetic acid with zinc:
Balanced molecular equation: Zn(s) + 2CH₃COOH(aq) → (CH₃COO)₂Zn(aq) + H₂(g).
Ionic equation: Zn(s) + 2H⁺(aq) + 2CH₃COO⁻(aq) → Zn²⁺(aq) + 2CH₃COO⁻(aq) + H₂(g).
Net ionic equation: Zn(s) + 2H⁺(aq) → Zn²⁺(aq) + H₂(g).
Zinc is oxidized from oxidation number 0 (Zn) to oxidation number +2 (Zn²⁺), hydrogen is reduced from oxidation number +1 to oxidation number 0 (H₂).
