(a) Some metallic oxides can be reduced by hydrogen, carbon, carbon monoxide and some cannot. Explain.

(b) Write balanced equation for the reduction of copper (II) oxide by hydrogen.

(a) The metals in the middle of the activity series such as iron, lead, copper, etc., are moderately reactive and are found as sulphides or carbonates in nature. They are obtained by the reduction of their oxides with carbon, carbon monoxide and hydrogen.
While, oxides of highly active metals like sodium and potassium have great affinity for oxygen and so cannot be reduced by common reducing agents like carbon, carbon monoxide or hydrogen.

(b) $\underset{\text{black}}{\text{CuO}} + \text{H}$2 \xrightarrow{\Delta} \underset{\text{pink/brown}}{\text{Cu}} + \text{H}{2}\text{{O}}