Question 3 Page 13 - Chapter 1 Class 10 - Chemical Reactions and Equations

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.