Question

A shiny brown coloured element A on heating in air becomes black due to the formation of a substance B.
When B reacts with a gas C, A is obtained again. C is the gas which is evolved at cathode during electrolysis
of water. Identify A, B and C and write the balanced chemical equations for the chemical reactions involved
in the process.

Answer 1

A is COPPER
B is COPPER OXIDE
C is OXYGEN
chemical equation- 2Cu+O2(i was not able to write the formula of oxygen)-2CuO

Answer 2

The shiny brown colour element is copper.
There is coating of black colour substance that is Copper oxide.
2Cu + O2 = 2CuO
Also the gas which is evolved at cathode during electrolysis of water is Hydrogen
Hope this help......
2H2O = 2H2 + O2