Question

For each of the following, does the oxidation number increase or decrease in the course of a redox reaction? (a) An oxidizing agent (b) A reducing agent (c) A substance undergoing oxidation (d) A substance undergoing reduction

Short answer

(a) Decreases, (b) Increases, (c) Increases, (d) Decreases.

Step-by-step solution

Define Oxidation Number

The oxidation number represents the total number of electrons that an atom either gains or loses to form a chemical bond. It is an indicator of the degree of oxidation of an atom in a chemical compound.

Understand Oxidizing Agent

An oxidizing agent is a substance that causes another substance to lose electrons, and itself gains electrons in the process. Thus, the oxidation number of an oxidizing agent decreases as it undergoes reduction.

Understand Reducing Agent

A reducing agent is a substance that causes another substance to gain electrons, and itself loses electrons in the process. Therefore, the oxidation number of a reducing agent increases as it undergoes oxidation.

Examine Substance Undergoing Oxidation

A substance that undergoes oxidation loses electrons. As a result, its oxidation number increases during the reaction.

Examine Substance Undergoing Reduction

A substance that undergoes reduction gains electrons. This causes its oxidation number to decrease during the reaction.

Key concepts

Oxidation Number

The oxidation number is a key concept in understanding redox reactions. It indicates how many electrons an atom gains or loses during a chemical reaction. By tracking the changes in oxidation numbers, we can identify which atoms are oxidized and reduced. This concept helps us understand the flow of electrons and predict the products of chemical reactions.

• The oxidation number increases if an atom loses electrons, indicating oxidation.
• The oxidation number decreases if an atom gains electrons, indicating reduction.

For example, in water (H₂O), oxygen has an oxidation number of -2, indicating it has gained electrons. Tracking these changes is crucial to determining the role of different substances in a reaction.

Oxidizing Agent

An oxidizing agent is a substance that causes another chemical to lose electrons during a redox reaction. Because it is gaining electrons itself, the oxidizing agent is reduced. This means its oxidation number will decrease. Understanding the role of oxidizing agents is important because they drive the oxidation process by accepting electrons from the other substance.

• Oxidizing agents have high electron affinity, meaning they easily gain electrons.
• Common examples include oxygen, hydrogen peroxide, and the halogens.

Identifying oxidizing agents in reactions can help determine which substances will be oxidized.

Reducing Agent

A reducing agent plays an opposite role compared to an oxidizing agent. It donates electrons to another substance, causing the reduction process. During this, the reducing agent itself is oxidized, meaning its oxidation number increases. This loss of electrons enables the corresponding substance in the reaction to gain electrons and be reduced.

• Reducing agents have low electron affinity and are keen to lose electrons.
• Common reducing agents include metals like sodium and magnesium.

Recognizing the reducing agents in reactions is vital for understanding which parts of the compound are gaining electrons.

Chemical Bonding

Chemical bonding is foundational in creating the interactions between atoms in redox reactions. Bonds form when electrons are shared or transferred between atoms. The type of bond influences how easily electrons are gained or lost in a reaction.

• Ionic bonds involve the transfer of electrons, resulting in a loss or gain of electrons by respective atoms and ions.
• Covalent bonds involve sharing electrons, maintaining a stronger control over the electrons involved.

Understanding different types of chemical bonds aids in predicting how substances might interact in redox reactions. It also helps identify potential oxidizing and reducing agents based on their bonding tendencies.