69 Oxidation-Reduction Reactions

Redox Reactions Introduction

LEARNING OBJECTIVES

Explain the processes involved in a redox reaction and describe what happens to their various components.

KEY TAKEAWAYS

Key Points

  • Oxidation and reduction reactions are defined by the movement of electrons

Key Terms

  • : a shorthand term for “reduction-oxidation,” two methods of electron transfer that always occur together

Redox reactions are all around us. In fact, much of our technology, from fire to laptop batteries, is largely based on redox reactions. Redox ( reduction – oxidation ) reactions are those in which the oxidation states of the reactants change. This occurs because in such reactions, electrons are always transferred between species. Redox reactions take place through either a simple process, such as the burning of carbon in oxygen to yield carbon dioxide (\text{CO}_2), or a more complex process such as the oxidation of glucose (\text{C}_2\text{H}_12\text{O}_6) in the human body through a series of electron transfer processes.

The term “redox” comes from two concepts involved with electron transfer: reduction and oxidation. These processes are defined as follows:

  • Oxidation is the loss of electrons or an increase in oxidation state by a molecule, atom, or ion.
  • Reduction is the gain of electrons or a decrease in oxidation state by a molecule, atom, or ion.

A simple mnemonic for remembering these processes is “OIL RIG”—Oxidation Is Losing (electrons), Reduction Is Gaining (electrons).

Redox reactions are matched sets: if one species is oxidized in a reaction, another must be reduced. Keep this in mind as we look at the five main types of redox reactions: combination, decomposition, displacement, combustion, and disproportion.

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