Classify each of the following unbalanced half-reactions as either an oxidation or a reduction. (a) O₂(g) → OH^-(aq)

Verified step by step guidance

1. Identify the oxidation states of the elements in the reactants and products. For O₂(g), the oxidation state of oxygen is 0. In OH^-(aq), the oxidation state of oxygen is -2.
2. Determine the change in oxidation state for oxygen. The oxidation state changes from 0 in O₂(g) to -2 in OH^-(aq).
3. Recognize that a decrease in oxidation state indicates a gain of electrons, which is characteristic of a reduction process.
4. Conclude that the half-reaction O₂(g) → OH^-(aq) is a reduction because oxygen is gaining electrons.
5. Remember that in a reduction half-reaction, the species undergoing reduction is the one that gains electrons.

Key Concepts

Oxidation and Reduction

Oxidation and reduction are chemical processes that involve the transfer of electrons between species. Oxidation refers to the loss of electrons, resulting in an increase in oxidation state, while reduction involves the gain of electrons, leading to a decrease in oxidation state. These processes are always coupled, meaning that when one species is oxidized, another must be reduced.

Half-Reactions

Half-reactions are equations that show either the oxidation or reduction process separately, allowing for a clearer understanding of electron transfer. In a half-reaction, the species being oxidized or reduced is explicitly shown along with the electrons involved. This method is particularly useful in balancing redox reactions and identifying the roles of different reactants.

Oxidation States

Oxidation states (or numbers) are a way to keep track of electrons in chemical reactions, particularly in redox processes. Each element in a compound is assigned an oxidation state based on its electron configuration and bonding. Changes in oxidation states during a reaction help determine which species is oxidized and which is reduced, providing insight into the overall reaction mechanism.