Question

(a) What would you observe if hydrogen gas is passed over heated copper (II) oxide?

(b) Which property of hydrogen is illustrated in (a)

(c) Give a balanced equation for the reaction taking place in (a)

(d) Mention one large scale use of the property named in (b)

Answer 1

(a)

• When oxides of metals such as iron, copper and zinc react with hydrogen, they get reduced to their corresponding metals. When copper(II) oxide reacts with hydrogen, it reduces into copper and water

$$\begin{gathered} \mathrm{CuO}\left(\mathrm{s}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)\to \mathrm{Cu}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Copper}\left(\mathrm{II}\right)\mathrm{oxide}\mathrm{Hydrogen}\mathrm{Copper}\mathrm{Water} \end{gathered}$$

(b) A reaction in which a metallic oxide loses its oxygen to form pure metal is called a reduction reaction. This property of hydrogen is called the reducing property.

(c)

• Number of atoms of each element on LHS

Copper = 1 atom, Oxygen = 1 atom, Hydrogen = 2 atoms

• Number of atoms of each element on RHS

Copper = 1 atom, Oxygen = 1 atom, Hydrogen = 2 atoms

• We can see that the number of atoms in LHS = the number of atoms in RHS

Therefore, the balanced chemical equation is $$\begin{gathered} \mathrm{CuO}\left(\mathrm{s}\right)+{\mathrm{H}}_2\left(\mathrm{g}\right)\to \mathrm{Cu}\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right) \\ \mathrm{Copper}\left(\mathrm{II}\right)\mathrm{oxide}\mathrm{Hydrogen}\mathrm{Copper}\mathrm{Water} \end{gathered}$$

(d)

• The reducing property is used in extracting pure metal from its ore.
• Therefore, large scale use of reducing property is Purification or extraction of metal from concentrated ore.