Classify the half‑reactions as reduction half‑reactions or oxidation half‑reactions.

H2(g)⟶2H+(aq)+2e−H2(g)⟶2H+(aq)+2e−

12O2(g)+2H+(aq)+2e−⟶H2O(g)12O2(g)+2H+(aq)+2e−⟶H2O(g)

Cd(s)+2OH−(aq)⟶Cd(OH)2(s)+2e−Cd(s)+2OH−(aq)⟶Cd(OH)2(s)+2e−

2NiO(OH)(s)+2H2O(l)+2e−⟶2Ni(OH)2(s)+2OH−(aq)2NiO(OH)(s)+2H2O(l)+2e−⟶2Ni(OH)2(s)+2OH−(aq)

Fe(s)⟶Fe2+(aq)+2e−Fe(s)⟶Fe2+(aq)+2e−

oxidation

reduction

reduction

oxidation

reduction