3.1.5 - Oxidation, reduction and redox equations

What can oxidation be?

Oxidation can be the addition of oxygen, loss of hydrogen or the loss of electrons.

What can reduction be?

Reduction can be the loss of oxygen, addition of hydrogen and the gain of electrons.

What happens if one species if oxidised?

If one species is oxidised, another must be reduced.

What is an oxidising agent?

An oxidising agent oxidises another atom or ion by causing it to lose electrons. An oxidising agent itself gets reduced.

What is a reducing agent?

A reducing agent is a substance that reduces another atom or ion by causing it to gain electrons, A reducing agent itself gets oxidised.

Can some substances be both reducing and oxidising agents?

yes

What is the oxidation state?

A number assigned to an element in chemical compound, which represents the number of electrons lost or gained by an atom of that element in the compound.

What can the oxidisation state be used to find out?

Tell if oxidation or reduction has taken place
Work out what has been oxidised and/or reduced
Construct half equations and balance redox equations.

What is the oxidising state of atoms?

Atoms have 0 as their oxidation state.

What is the oxidising state in simple ions?

In simple ions, the oxidation state of the atom is the charge on the ion.

What is the oxidising number of oxygen and the exceptions?

Oxygen is -2 except in peroxides where it is -1 and in F2O where it is +2

What is the oxidising number of hydrogen and the exceptions?

Hydrogen is +1 except for metal hydrides where it is -1

What is the oxidising number of chlorine and the exceptions?

Cl is -1 except in compounds with F and O where it is positive

What is the sum of the oxidation state in a compound?

Zero

What is the sum of the oxidation state in an ion?

the charge on the ion

Which element is given the negative value?

In a compound or an ion, the more electronegative element is given the oxidation state. This element is given the negative value.

Which atoms can only have integer oxidation states?

Single atoms can only have an integer oxidation states.

What does a positive number mean?

A positive number shows that the element has lost electrons and has therefore been oxidised.

What does a negative number mean?

A negative number shows that the element has gained electrons and has therefore been reduced.

What does a gain of electrons do to the oxidation number?

decreases

What is a redox reaction?

an oxidation reaction paired with a reduction reaction