Question

A brown substance 'X' on heating in air forms a substance 'Y'. When hydrogen gas is passed over heated 'Y', it again changes back into 'X'.
(i) Name the substance 'X' and 'Y'.
(ii) Name the type of chemical reactions occurring during both the changes.
(iii) Write the chemical equations of the reactions.

Answer 1

(I) Substance X is 'Copper' and substance Y is 'Copper oxide'.

(ii) When copper is heated in air, oxidation takes place. When hydrogen gas is passed over heated copper oxide, reduction takes place.

(iii) The chemical equations involved are:-

2Cu (s) + O₂ (g) ----> 2CuO

CuO + H₂ (g) ----> Cu + H₂O