Question

In each of the following, tell whether the substance gains electrons or loses electrons in a redox reaction: (a) An oxidizing agent (b) A reducing agent (c) A substance undergoing oxidation (d) A substance undergoing reduction

Short answer

(a) Gains electrons, (b) Loses electrons, (c) Loses electrons, (d) Gains electrons.

Step-by-step solution

Understand the Terminology

First, we need to clarify the terms used in the exercise. **Oxidation** refers to the loss of electrons, while **reduction** refers to the gain of electrons. An **oxidizing agent** is a substance that causes another substance to oxidize and in the process is itself reduced (gains electrons). A **reducing agent** causes another substance to reduce and is oxidized itself (loses electrons).

Analyzing the Oxidizing Agent

An **oxidizing agent** gains electrons because it is reduced in the chemical reaction that allows it to oxidize another substance.

Analyzing the Reducing Agent

A **reducing agent** loses electrons because it donates electrons to another substance, causing the reducing agent itself to oxidize.

Substance Undergoing Oxidation

A substance undergoing **oxidation** loses electrons, as oxidation is defined as the loss of electrons in a chemical reaction.

Substance Undergoing Reduction

A substance undergoing **reduction** gains electrons, as reduction is defined as the gain of electrons in a chemical reaction.

Key concepts

Oxidizing Agent

An oxidizing agent plays a crucial role in redox reactions, which involve the transfer of electrons between substances. This agent is responsible for causing another substance to lose electrons.

In doing so, the oxidizing agent accepts electrons and becomes reduced. It's like playing a game of "pass the parcel," where the oxidizing agent ends up with the electrons as the prize.

To remember this more easily, think of the oxidizing agent as the electron "completer," because it gains what it needs by accepting electrons.

• Causes another substance to oxidize
• Gains electrons
• Becomes reduced

In everyday life, one common example of an oxidizing agent is oxygen itself. In many reactions, oxygen gains electrons from other substances and facilitates their oxidation.

When learning or working with redox reactions, noting which species acts as the oxidizing agent is essential for understanding the overall electron flow.

Reducing Agent

A reducing agent is essential for redox reactions as it facilitates the reduction of another substance. It does this by donating electrons, quite generously, to the substance needing them.

This generous act simultaneously causes the reducing agent to lose its electrons, thus becoming oxidized itself. It's a bit like a person giving away their lunch to someone else and then having no lunch themselves.

Think of a reducing agent as the "electron benefactor," as it willingly parts with electrons to help another.

• Causes another substance to reduce
• Loses electrons
• Becomes oxidized

Hydrogen is often used as a reducing agent in various chemical processes, donating its electrons and getting oxidized to form bonds with other elements.

In any redox reaction, identifying which species is the reducing agent helps in predicting the direction of electron movement and the reaction’s outcome.

Oxidation

Oxidation is one half of the redox reaction pair and it signifies the loss of electrons from a substance.

When oxidation occurs, the oxidized substance hands over its electrons and often experiences an increase in oxidation state. It's a bit like letting go of a balloon and watching it float away, never to be seen again.

This process is key in many everyday phenomena, such as rusting, where iron loses electrons to oxygen.

• Involves electron loss
• Oxidation state increases

One simple way to remember oxidation is through the mnemonic: OIL - Oxidation Is Loss (of electrons).

Learning to identify oxidation in reactions helps in balancing redox equations and understanding how substances interact in chemical processes.

Reduction

Reduction is the counterpart to oxidation in redox reactions. It signifies the gain of electrons by a substance from another.

During reduction, the substance becomes more "complete" in terms of electron count, experiencing a decrease in oxidation state, much like a hole being filled with dirt.

This action is the reverse of oxidation and is crucial in processes like photosynthesis, where carbon dioxide is reduced to form glucose.

• Involves electron gain
• Oxidation state decreases

Remembering reduction can be simplified with the mnemonic: RIG - Reduction Is Gain (of electrons).

Focusing on reduction in reactions allows for a deeper understanding of how substances are transformed and how energy is transferred in a chemical system.