Classify the half‑reactions as reduction half‑reactions or oxidation half‑reactions. h2(g)⟶2h+(aq)+2e− 12o2(g)+2h+(aq)+2e−⟶h2o(g) cd(s)+2oh−(aq)⟶cd(oh)2(s)+2e− 2nio(oh)(s)+2h2o(l)+2e−⟶2ni(oh)2(s) +2oh−(aq) fe(s)⟶fe2+(aq)+2e−

See explanation...

Explanation:

To ID half-rxns as oxidation or reduction, look where the electrons are posted in the equation... That is,

if the electrons are on the product side of the equation => oxidation rxn

if the electrons are on the reactant side of the equation => reduction rxn

=> give a look at the equations in your post... you should be able to see the electrons listed and assign oxidation or reduction definitions. now :-)