Describe the differences between half-cell reactions and redox equations.

Half-cell reactions involve the transfer of electrons between species, while redox equations show the overall transfer of electrons in a chemical reaction.

Half-cell reactions are the individual reactions that occur at each electrode in an electrochemical cell. They involve the transfer of electrons between species, with one species being oxidized (loses electrons) and the other being reduced (gains electrons). These reactions are written as half-equations, with the species involved in the oxidation or reduction reaction written on either side of the equation. For example, the half-equation for the oxidation of zinc in a zinc-copper cell is: Zn(s) → Zn2+(aq) + 2e-.

Redox equations, on the other hand, show the overall transfer of electrons in a chemical reaction. They combine the half-cell reactions for the oxidation and reduction reactions to give a balanced equation for the overall reaction. Redox equations are written in terms of the reactants and products, with the electrons transferred shown as a separate entity. For example, the redox equation for the reaction between zinc and copper in a zinc-copper cell is: Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s).

In summary, half-cell reactions show the individual electron transfer reactions that occur in an electrochemical cell, while redox equations show the overall transfer of electrons in a chemical reaction.