Question

What is the colour of the product formed when the black copper oxide is heated in a steam of hydrogen?

• A. Greenish red
• B. Grey
• C. Pale yellow
• D. Reddish brown

Answer 1

The correct option is D

Reddish brown

Black copper oxide, when heated in a steam of hydrogen forms a reddish-brown copper metal. The reaction involved in the process is:

$\underset{\left(\text{Black}\right)}{\text{CuO}\text{(s)}}+{\text{H}}_2\text{(g)}\to \underset{\left(\text{Reddish brown}\right)}{\text{Cu}\text{(s)}}+{\text{H}}_2\text{O}\text{(l)}$

The copper oxide is reduced to copper on the account of loss of oxygen on the other hand hydrogen has been oxidised on the account of gain of oxygen to form water.