Topic 3: Redox I 1️⃣&2️⃣

Oxidation

A species that oxidises another species by removing one or more electrons. When an oxidising agent reacts it gains electrons and is therefore, reduced

A species that reduces another species by adding one or more electrons. When an reducing agent reacts it loses electrons and is therefore, oxidised

Simultaneous oxidation and reduction of an element in a single reaction

A reaction that involves both reduction and oxidation

The change that an ion has or the change that it would have if the species was fully ionic

-1

Combined with a less electronegative element. Then it becomes -1

Peroxides where it is -1 and when combined with fluorine it is +1

0

More electronegative element in a substance

OxIdised

ReDuced

When an element can have more than one oxidation state the names of its compounds and its ions often include the oxidation number of that element eg. FeCl2 = iron (II) chloride (oxidation number of Fe= +2) FeCl3 = iron (III) chloride (oxidation number of Fe= +3)

The formula of the iron(III) ion is Fe3+ The formula for the sulphate ion is SO4 2- So the two ions are present in a 2:3 ratio to give a neutral compound giving the formula Fe2(SO4)3

Write a balanced equation for the species Work out the ‘before’ and ‘after’ oxidation states Balance oxidation states with electrons If charges don’t balance add H+ ions to one of the sides to balance If still not balanced add enough H2O to one side so it balances