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Redox Equations

You can use oxidation numbers to help you understand redox reactions.You can also use oxidation numbers to help balance ionic equations.For an equation to be balanced:

the number of each type atom must be the same for both products and reactants.
the total charge of the reactants must be the same as the total charge of the products.

In the following redox equation:

+3		-1	→	+2		0
Fe³⁺	+	I^-	→	Fe²⁺	+	½I₂

Iron is reduced from +3 to +2 and iodine is oxidised from -1 to 0.In the following redox equation:+

+5-2		+1+4-2	→	0		+6-2		+1		+1-2
2IO₃^-	+	5HSO₃^-	→	I₂	+	5SO₄^2-	+	3H⁺		H₂O

iodine is reduced from +5 to 0 and sulfur is oxidised from +4 to +6.

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Specification: AQA Chemistry (7404), AS-level, 3.1.7 Oxidation, reduction and redox equations. Topic: Oxidation and Reduction.

Key terms in this lesson

Ionic equation: An equation that shows only the particles that react, leaving out spectator ions.
Oxidation: The addition of oxygen, the removal of hydrogen, the loss of electrons, or an increase in oxidation number.
Oxidation number: A number that represents the number of electrons an atom has lost or gained, or would do if the compound were fully ionic.

More in Oxidation and Reduction

All 15 lessons in Oxidation and Reduction · All AQA AS-level Chemistry topics