Question

How do chemists define the processes of oxidation and reduction? Write a simple equation illustrating each of your definitions.

Short answer

Chemists define oxidation as the process in which a chemical species loses electrons, resulting in an increase in the oxidation state of the species. In contrast, reduction is the process in which a chemical species gains electrons, leading to a decrease in the oxidation state. An example of oxidation is the reaction between magnesium (Mg) and oxygen (O₂), resulting in magnesium oxide (MgO): \[2\,Mg (s) + O_2 (g) \rightarrow 2\,MgO (s)\] An example of reduction is the reaction between copper(II) oxide (CuO) and hydrogen (H₂), which produces copper (Cu) and water (H₂O): \[CuO (s) + H_2 (g) \rightarrow Cu (s) + H_2O (l)\]

Step-by-step solution

1. Define Oxidation process

Oxidation is defined as the process in which a chemical species loses electrons. This loss of electrons results in an increase in the oxidation state of the species.

2. Define Reduction process

Reduction is defined as the process in which a chemical species gains electrons. This gain of electrons results in a decrease in the oxidation state of the species.

3. Write an Equation illustrating Oxidation process

A simple example of an oxidation process is the reaction of magnesium with oxygen to form magnesium oxide. The balanced chemical equation for this reaction is: \[2\,Mg (s) + O_2 (g) \rightarrow 2\,MgO (s)\] This reaction is an example of an oxidation process because magnesium loses electrons by forming a positive ion with an increased oxidation state of +2. Magnesium's initial oxidation state is 0, and after the reaction, the magnesium ion in magnesium oxide has an oxidation state of +2.

4. Write an Equation illustrating Reduction process

A simple example of a reduction process is the reaction of copper(II) oxide with hydrogen to form copper and water. The balanced chemical equation for this reaction is: \[CuO (s) + H_2 (g) \rightarrow Cu (s) + H_2O (l)\] This reaction is an example of a reduction process because copper in copper(II) oxide has an initial oxidation state of +2. After the reaction, the oxidation state of copper decreases to 0 as it forms solid copper. The copper(II) ion gains electrons from hydrogen during the reaction, and its oxidation state decreases, illustrating a reduction process.

Key concepts

Oxidation

Oxidation is a fundamental concept in chemistry, primarily described as the process in which an element or compound loses electrons. This loss of electrons is crucial because it results in an increase in the oxidation state of the chemical species involved. Imagine an atom shedding off these negatively charged particles, causing it to become more positively charged. For example, when magnesium (\(Mg\)) reacts with oxygen (\(O_2\)), it forms magnesium oxide (\(MgO\)). During this reaction, each magnesium atom loses two electrons, changing its oxidation state from 0 to +2. The equation is \(2\,Mg (s) + O_2 (g) \rightarrow 2\,MgO (s)\). This shows a classic example of oxidation, with magnesium increasing its oxidation state by undergoing electron loss.

Reduction

Reduction is often thought of as the opposite of oxidation. It involves the gain of electrons by an atom or molecule. When a species undergoes reduction, it decreases its oxidation state, which means it becomes less positive (or more negative, depending on your perspective). For instance, in the transformation of copper(II) oxide (\(CuO\)) to copper (\(Cu\)), copper starts by having an oxidation state of +2. During the reaction with hydrogen (\(H_2\)), copper gains electrons, leading to a reduction in its oxidation state to 0. The balanced reaction for this is \(CuO (s) + H_2 (g) \rightarrow Cu (s) + H_2O (l)\). This illustrates how the gain of electrons by copper results in reduction.

Oxidation State

The term "oxidation state" is a way to describe the degree of oxidation of an atom in a chemical compound. It represents the number of electrons an atom would gain or lose if the compound was perfectly ionic. Each change in oxidation state reflects either a transfer of electrons or a shift in electron density. A positive oxidation state indicates a loss of electrons, while a negative one suggests an electron gain. For magnesium in \(MgO\), the oxidation state of +2 indicates it has lost two electrons. Similarly, for copper in \(CuO\), starting from an oxidation state of +2 to 0 implies a gain of two electrons. Understanding oxidation states helps chemists predict reactive behaviors and balance chemical reactions precisely.

Electron Transfer

Electron transfer is at the heart of both oxidation and reduction processes. These movements of electrons between atoms or molecules are what change the oxidation states. By either gaining or losing electrons, species participating in a chemical reaction undergo changes in their charge balance. Electrons move from one entity to another, often facilitating energy transfer as they do so.

• In oxidation, electrons are shed, leading to an increase in oxidation state.
• In reduction, electrons are gained, resulting in a decrease in oxidation state.

For example, in our earlier mentioned reactions, magnesium transfers electrons to oxygen during oxidation, while copper gains electrons from hydrogen in reduction. This electron dance is essential to numerous chemical and biological processes, making electron transfer a pivotal study area in chemistry.