Classify each of the following unbalanced half-reactions as either an oxidation or a reduction. (b) H₂O₂(aq) → O₂₍g)

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1. Identify the oxidation states of the elements in the reactants and products. For H₂O₂, hydrogen is +1 and oxygen is -1. For O₂, oxygen is 0.
2. Determine the change in oxidation state for the element of interest. Here, focus on oxygen: it changes from -1 in H₂O₂ to 0 in O₂.
3. Recognize that an increase in oxidation state indicates oxidation, while a decrease indicates reduction.
4. Since the oxidation state of oxygen increases from -1 to 0, this half-reaction involves oxidation.
5. Classify the half-reaction H₂O₂(aq) → O₂(g) as an oxidation process.

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 undergoing oxidation will show a loss of electrons, while the species undergoing reduction will show a gain. This method is particularly useful in balancing redox reactions and identifying the roles of different reactants.

Oxidation States

Oxidation states (or oxidation numbers) are assigned to atoms in a compound to indicate their degree of oxidation or reduction. They help in determining how many electrons are lost or gained during a reaction. In the case of H2O2 → O2, analyzing the oxidation states of oxygen in both species reveals that oxygen in H2O2 has a lower oxidation state than in O2, indicating that it is being oxidized.