Question

(a) What is meant by the term reduction? (b) On which side of a reduction half-reaction do the electrons appear? (c) What is meant by the term reductant? (d) What is meant by the term reducing agent?

Short answer

(a) Reduction is a chemical process where a substance gains electrons or has a decrease in its oxidation state during a redox reaction. (b) In a reduction half-reaction, electrons appear on the reactant side (left side) of the equation, as they are gained by the species undergoing reduction. (c) A reductant or reducing agent is a species that loses electrons in a redox reaction and causes the reduction of another species. It donates electrons to another substance, thus getting oxidized itself in the process.

Step-by-step solution

(a) Definition of Reduction

Reduction is a chemical process in which a substance gains electrons or has a decrease in its oxidation state during a redox (reduction-oxidation) reaction. In other words, it is the process of the transfer of electrons from one species to another, where the species that gains electrons is said to be reduced.

(b) Electrons Appearing on side of a Reduction Half-Reaction

In a reduction half-reaction, electrons appear on the reactant side (left side) of the equation. This is because they are involved in the reaction to be gained by the species that is undergoing reduction. The general representation of a reduction half-reaction is: $$O{x}_e^{+}+n{e}^{-}\to Red$$ Where $O{x}_e^{+}$ is the oxidized species, $n$ is the number of electrons transferred, $Red$ is the reduced species, and $e^{-}$ is the electron.

(c) Definition of Reductant

A reductant, also known as a reducing agent, is a species that loses electrons in a redox reaction and causes the reduction of another species. In simpler terms, a reductant is a substance that donates electrons to another substance in a redox reaction, thus getting oxidized itself in the process.

(d) Definition of Reducing Agent

A reducing agent or reducing substance is a species that causes the reduction of another substance by donating electrons to it during a redox reaction. The reducing agent gets oxidized in the process as it loses electrons. It's important to note that a reducing agent and reductant are essentially the same thing and can be used interchangeably.