Question

on passing hydrogen gas over the heated black material coating on the surface of copper sheets- give reason

Answer 1

Answer:

On passing Hydrogen gas over the heated black material coating on the surface of copper sheets :

It becomes Brown due to copper formation

Explanation:

Copper reacts with atmospheric Oxygen (Moisture) and gets black because of the formation of copper oxide (CuO). This reaction is also called oxidation reaction .

$2Cu(s) + O_{2}(g)\rightarrow 2CuO$

On passing Hydrogen gas over the heated black material coating on the surface of copper sheets this black coating become brown. This is due to formation of Copper again. This is redox- reaction.

Here copper oxide  is reduced  to copper and Hydrogen is oxidised water.

$CuO + H_{2}\rightarrow Cu + H_{2}O$