Question

Identify the substances oxidised and reduced in the following reactions:

(i) 4Na (s) + O₂ (g) → 2Na₂O (s)

(ii) CuO (s) + H₂ (g) → Cu (s) + H₂O (l)

Answer 1

(i) In this given reaction, 4Na (s) + O₂ ​(g) → 2Na_2​O (s) 

Sodium (Na) is gaining oxygen to form Na_2​O. Hence, sodium (Na) is being oxidized and oxygen is getting reduced (oxygen is a reduced substance).

2Na → Na₂​O

Additional information:

• The substance that gains oxygen is being oxidised and is the oxidised substance.
• The substance that loses oxygen is being reduced and is the reduced substance.

(ii) CuO (s) + H₂ (g) → Cu (s) + H₂O (l)

• Oxygen is added to H₂, and it gets oxidized to H₂O. Therefore, H₂ gets oxidized.
• Oxygen is removed from CuO, and it gets reduced to Cu. Therefore, CuO gets reduced.