Question

Use the following reaction to define the terms redox reaction, half-reaction, oxidizing agent, and reducing agent: \(4 \mathrm{Na}(s)+\mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{Na}_{2} \mathrm{O}(s)\)

Short answer

This reaction is a redox reaction; Na is the reducing agent, and \(\mathrm{O}_2\) is the oxidizing agent.

Step-by-step solution

Understand the Reaction

The given chemical reaction is \(4 \mathrm{Na}(s) + \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{Na}_{2} \mathrm{O}(s)\). This process describes sodium (Na) reacting with oxygen (\(\mathrm{O}_2\)) to form sodium oxide (\(\mathrm{Na}_2\mathrm{O}\)). This is a redox reaction, involving both reduction and oxidation processes.

Define Redox Reaction

A redox reaction is a chemical reaction in which the oxidation states of atoms are changed. In this reaction, sodium is being oxidized from 0 to +1, while oxygen is reduced from 0 to -2.

Identify the Half-Reactions

Separate the reaction into two half-reactions to identify which elements are oxidized and which are reduced. For the oxidation half-reaction: \(4 \mathrm{Na} \rightarrow 4 \mathrm{Na}^{+} + 4 \mathrm{e}^-\). For the reduction half-reaction: \(\mathrm{O}_2 + 4 \mathrm{e}^- \rightarrow 2 \mathrm{O}^{2-}\).

Identify the Oxidizing Agent

The oxidizing agent is the substance that gets reduced and gains electrons. In this reaction, oxygen (\(\mathrm{O}_2\)) is the oxidizing agent because it gains electrons.

Identify the Reducing Agent

The reducing agent is the substance that gets oxidized and loses electrons. Sodium (Na) is the reducing agent because it loses electrons.

Key concepts

Oxidizing Agent

In a redox reaction, the oxidizing agent is the substance that promotes oxidation by accepting electrons. Simply put, it is the partner in the reaction that gains electrons and, in the process, gets reduced. Let's look at the equation: \(4 \mathrm{Na}(s) + \mathrm{O}_{2}(g) \longrightarrow 2 \mathrm{Na}_{2} \mathrm{O}(s)\). Here, oxygen starts with an oxidation state of 0 and ends with -2 as it transforms into oxide ions, \(\mathrm{O}^{2-}\).

This change signals oxygen's role as the oxidizing agent. It effectively "steals" electrons from sodium, driving the overall reaction forward. The oxidizing agent is crucial because, by gaining electrons, it pushes another species to lose electrons—characterizing the interplay of reduction and oxidation. Understanding the function of an oxidizing agent helps us grasp why and how certain substances are transformed in chemical processes. Recognizing this allows for better predictions and control over chemical reactions.

Reducing Agent

The reducing agent in a redox reaction is the substance that donates electrons to another species, leading to its oxidation. In the discussed reaction, sodium (\(\mathrm{Na}\)) performs this crucial role. Sodium begins with an oxidation state of 0, as it is in its metallic form, and ends with a +1 oxidation state upon forming \(\mathrm{Na}^{+}\) ions in \( \mathrm{Na}_2 \mathrm{O} \).

This change occurs because sodium loses electrons during the process, thus it is the reducing agent. A helpful way to remember this is that the reducing agent itself gets oxidized. By losing electrons, the reducing agent enables another substance to undergo reduction, fostering the electron transfer essential for a redox reaction. Understanding sodium's role in oxidation provides insight into its reactive nature—why it so readily forms compounds with other substances. Such insights are valuable for anticipating chemical behaviors.

Half-Reaction

To understand redox reactions, breaking them into half-reactions is an insightful strategy. Each half-reaction reveals details about the transfer of electrons. In our example reaction, let's consider the component half-reactions.

• The oxidation half-reaction can be represented as: \(4 \mathrm{Na} \rightarrow 4 \mathrm{Na}^{+} + 4 \mathrm{e}^-\). In this, sodium loses electrons, indicating oxidation.
• The reduction half-reaction is: \(\mathrm{O}_2 + 4 \mathrm{e}^- \rightarrow 2 \mathrm{O}^{2-}\). Here, oxygen gains electrons, which means it's reduced.

By analyzing the half-reactions, we see the dual nature of redox processes; one part cannot occur without the other. Understanding half-reactions clarifies how substances are transformed and why balancing them is important to conservation laws in chemistry. They represent the core exchange of electrons and depict the broader picture of the chemical changes occurring.