what is half.cell reaction ?
Half cell reactions: A half reaction is either the oxidation or reduction reaction component of a redox reaction. A half reaction is obtained by considering the change in oxidation states of individual substances involved in the redox reaction.
Placing a piece of reactant in an electrolyte solution makes a half cell. Unless it is connected to another half cell via an electric conductor and salt bridge, no reaction will take place in a half cell.
On the cathode, reduction takes place.
Oxidant + n e- → Reductant
Example: Cu2+ + 2 e → Cu
Cu2+ is the oxidizing agent and Cu the reducing agent.
On the anode, oxidation takes place.
Reductant → n e- + Oxidant
Example: Zn → Zn2+ + 2 e-.
Zn is the reducing agent, and Zn2+ the oxidizing agent.