A reddish brown coloured metal used in electric wires, when powdered and heated strongly in an open China dish, its colour rums black. When hydrogen gas is passed over this black substance, it regains its original colour. Based on this information, the metal and black coloured substances are
The only reddish brown colour metal among the given options is copper. When copper powder is heated in a china dish it gets oxidized and turns black due to the formation of copper oxide (CuO). The reaction involved is:
2CuO + O2→ 2CuO
When H2 gas is passed over CuO, it gets reduced to Cu and thus regains its original colour.
CuO + H2→ Cu + H2O