If a substance gains oxygen in a reaction, it has been
oxidised. If it loses oxygen, it has been reduced.
Oxidation and reduction always take place together,
so if one substance is oxidised, another is reduced.
a First, see if you can write a word equation for
each redox reaction A to F below.
b Then, using the ideas above, say which
substance is being oxidised, and which is being
reduced, in each reaction.
A Ca (s) 1 O2 (g) 2 CaO (s)
B 2CO (g) 1 O2 (g) 2CO2 (g)
C CH4 (g) 1 2O2 (g) CO2 (g) 1 2H2O (l)
D 2CuO (s) 1 C (s) 2Cu (s) 1 CO2 (g)
E 2Fe (s) 1 3O2 (g) 2Fe2O3 (s)
F Fe2O3 (s) 1 3CO (g) 2Fe (s) 1 3CO2 (g)