Redox reactions.

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Oxidation-Reduction Reactions “Redox”

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Presentation transcript:

Redox reactions

First things to do with your reaction Firstly balance your equation Next: Calculate the oxidation number of each atom. Remember, compounds have an overall oxidation state of 0 (unless otherwise specified) In compounds H=+1 and O is usually -2

How to identify the oxidised atom OILRIG Oxidation is losing electrons So the atom which has an oxidation number that is increasing is the oxidised atom

How to identify the Reduced atom OILRIG Reduction is gaining electrons So the atom which has an oxidation number that is decreasing is the reduced atom

Example Ca (s) + H2SO4 (aq) CaSO4(aq) + H2 (g) So 0 +2 +6 -8 +2 +6 -8 0 So Calcium 0 +2 therefore Ca is oxidised Hydrogen +1 0 therefore H is reduced

How to identify the oxidising agent Now you have identified what is being oxidised and what is being reduced. An oxidising agent is the part of the equation that causes oxidation by taking electrons from something else Therefore the compound that contains the object that is reduced is the oxidising agent! In the case of our example it is sulphuric acid (acids are often the oxidising agent because they contain H+ ions)

Oxidising agent reduced = OAR

How to identify the reducing agent Now you have identified what is being oxidised and what is being reduced. An reducing agent is the part of the equation that causes reduction by giving electrons to something else Therefore the compound that contains the object that is oxidised is the reducing agent! In the case of our example it is calcium