IB Chemistry home > Syllabus 2016 > Redox processes > Redox equations

Syllabus ref: 9.1

Redox is a term that stands for 'Reduction and Oxidation'. In any reduction process electrons are provided and, logically, they must be picked up by a different species.

In other words, reduction always take place in conjunction with oxidation during redox chemical reactions (as opposed to processes occurring at electrodes). This chapter looks at redox equations and how to construct and deconstruct them.

Nature of science:

How evidence is used: Changes in the definition of oxidation and reduction from one involving specific elements (oxygen and hydrogen), to one involving electron transfer, to one invoking oxidation numbers is a good example of the way that scientists broaden similarities to general principles.


The activity series ranks metals according to the ease with which they undergo oxidation.

The Winkler Method can be used to measure biochemical oxygen demand (BOD), used as a measure of the degree of pollution in a water sample.

Applications and skills

Identification of the species oxidized and reduced and the oxidizing and reducing agents, in redox reactions.

Deduction of redox reactions using half-equations in acidic or neutral solutions.

Deduction of the feasibility of a redox reaction from the activity series or reaction data.

Solution of a range of redox titration problems.

Application of the Winkler Method to calculate BOD.

In Chapter 9.2