why half cell reactions are given in reduction reations by IUPAC?

Half-cell reactions are given in reduction reactions by IUPAC because reduction reactions are commonly used to represent electrochemical processes. In an electrochemical cell, which consists of two half-cells, oxidation occurs at one electrode (anode) and reduction occurs at the other electrode (cathode).

To represent the half-cell reactions, IUPAC prefers to use reduction half-reactions because they involve the gain of electrons, which is more intuitive and easier to understand. The reduction half-reaction shows the reactant species gaining electrons to form the product species, indicating the reduction process.

By convention, the reduction half-reaction is written on the right-hand side of the cell notation, while the oxidation half-reaction is written on the left-hand side. This allows for the net cell reaction to be represented properly, with the reduction half-reaction occurring at the cathode and the oxidation half-reaction occurring at the anode.

Using the reduction half-reaction also allows for easier comparison and analysis of different electrochemical processes. It allows scientists to focus on the species being reduced and their corresponding electron-transfer events.

To determine the half-cell reactions, one can consider the overall redox reaction and then separate it into two half-reactions, one for oxidation and the other for reduction. The half-reaction for reduction is often found in tables of standard reduction potentials, which provide the standard reduction potential values for various species. These potentials help determine the direction of electron flow and the spontaneity of the redox reaction.

In summary, IUPAC uses reduction half-reactions to represent half-cell reactions in electrochemical processes because they are more intuitive, easier to understand, and allow for proper representation of the overall redox reaction in an electrochemical cell.