Identify the substances that are oxidised and the substances that are reduced in the following reactions.
(i) 4Na(s) + O 2 (g) → 2Na 2 O(s)
(ii) Cu(s) + H 2 (g) → Cu(s) + H 2 O(l)
Answer
Addition of Oxygen to a Substance or removal of Hydrogen from a substance is called Oxidation.
Removal of Oxygen from a substance or addition of Hydrogen to a substance is called Reduction.
(i) 4Na(s) + O 2 (g) → 2Na 2 O(s)
Oxygen is added to Na, and it gets oxidized to Na 2 O.
Therefore, Na gets oxidized .
One atom of Oxygen is removed from O 2 , and it gets reduced to Na 2 O.
Therefore, O 2 gets reduced.
(ii) CuO(s) + H 2 (g) → Cu(s) + H 2 O(l)
Oxygen is added to H 2 , and it gets oxidized to H 2 O.
Therefore, H 2 gets oxidized .
Oxygen is removed from CuO, and it gets reduced to Cu.
Therefore, CuO gets reduced.
