Question

A reddish brown coloured metal used in electrical wire when heated turns black. when hydrogen gas is passed over this black substance , it regains its original colour . name the metal and represent the reaction .

Answer 1

it is copper
when it is heated it forms copper oxide
and when hydrogen is paased over this compound again it turns into a single one that is copper
reaction are as follows
copper+oxygen -gives CuO
CuO+H---GIVES-- C+H20