Question

A reddish brown metal used in electrical wires when powdered and heated strongly turns black. When hydrogen gas is passed over this black substance, it regains its original colour. Based on this information answer the following questions:

1. Name the metal and the black substance formed.
2. Write balanced chemical equations for the two reactions involved in the above information

Answer 1

1. The metal is called copper (Cu), and the black substance generated is called copper oxide.
2. The balanced chemical reactions for both the reactions are as follows:
   When powdered copper is heated strongly in the presence of oxygen copper oxide is.
   \[\ce{2Cu(s) + O_2(g) ->[\Delta]2CuO(s)}\]
   When hydrogen gas is passed over copper oxide, it produces copper metal and water.
   \[\ce{CuO(s) + H_2(g) ->Cu(s) + H_2O(l)}\]