Which of the following unbalanced half-reactions is correctly labeled as an oxidation or reduction? (a) NO₃^- (aq) → NO(g); reduction (b) Zn(s) → Zn²⁺(aq); reduction (c) ClO₃^-(aq) → Cl₂(g); oxidation (d) Br^-(aq) → Br₂(l); 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. Understanding these processes is crucial for identifying half-reactions in redox reactions.

Half-reactions are equations that show either the oxidation or reduction process separately. They are used to balance redox reactions by clearly indicating the species that are oxidized and reduced. Each half-reaction must be balanced for both mass and charge, which is essential for determining the correct labeling of oxidation and reduction.

Oxidation states (or numbers) are assigned to atoms in a compound to indicate their degree of oxidation or reduction. These states help in tracking electron transfer during chemical reactions. By analyzing the changes in oxidation states of the elements involved, one can determine whether a reaction is an oxidation or reduction process.