Topic 3 Redox I

Electrons are transferred when reduction and oxidation occurs. OILRIG Oxidation is the Loss of electrons Reduction is the gain of electrons

This is when reduction and oxidation happen at the same time. Ca + 1/2 O2 —-> CaO is a redox reaction Ca—-> Ca2+ + 2e- Calcium is being oxidised as it is losing electrons 1/2 O2 +2e- —–> O2- oxygen is being reduced as it is gaining electrons

They lose electrons and are oxidised themselves They gain electrons and are reduced themselves

Uncombined elements are always 0 Oxidation number is same as charge on the ion Group 1 and 2 is always +1 and +2 Aluminium is always +3 Hydrogen is always +1 except in hydrides where it is -1. Chlorine is always -1 except if it is in a compound with F and O, it would have a positive value Fluorine is always -1 Oxygen is -2 except it is -1 in peroxides and +2 in OF2

Oxidation is an increase in the oxidation number Reduction is a decrease in the oxidation number

Write down the species before and after a reaction Balance any atoms apart from oxygen and hydrogen Balance any oxygens with H2O Balance any hydrogens with H+ Balance charges with electrons e-

Write them both out and then make sure the electrons balance. Do this by multiplying the entire equations. Then cancel the electrons and combine the 2 equations Your full ionic equation shows both reduction and oxidation and so is a redox reaction

This is when reduction and oxidation simultaneously happens