Question

how has the black coating of copper oxide be turned reddish Brown ​

Answer 1

Answer:

This happens due to oxidation.

Explanation:

Copper from the vessel combines with oxygen present in air to form copper oxide. Since copper oxide is reddish brown in colour it forms a reddish brown layer on the black surface of the copper vessel.

hope it helps

Answer 2

Answer:

hey buddy

when hydrogen gas is passed over a black coloured substance 'X', the coating of on its surface turns brown. this is due to: ... The substance X is copper (II) oxide (CuO). Copper metal is reddish brown in colour and when burnt it air, it turns black due to the formation of copper oxide.