Question

In the redox reaction

$\mathrm{Fe}\left(\mathrm{s}\right)+{\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)\to \mathrm{Cu}\left(\mathrm{s}\right)+{\mathrm{Fe}}^{2+}$

Which one of Cu and Fe is more reactive?

Answer 1

1. Redox reactions

A redox reaction involves the process of oxidation and reduction simultaneously. In redox reactions, the oxidation number of the elements gets changed. Elements that lose electrons in a redox reaction are called reducing agents. These reagents undergo oxidation and will have lower ionization enthalpy. Since metals with low ionization enthalpy are more reactive, the reducing agent will be the more reactive metal in a redox reaction.

2. Reaction of Iron in Copper solution

Single displacement reactions are examples of redox reactions. The reaction between Iron and Copper ions is given as:

$$\begin{gathered} \mathrm{Fe}\left(\mathrm{s}\right)+{\mathrm{Cu}}^{2+}\left(\mathrm{aq}\right)\to \mathrm{Cu}\left(\mathrm{s}\right)+{\mathrm{Fe}}^{2+}\left(\mathrm{aq}\right) \\ \mathrm{Iron}\mathrm{Copper}\mathrm{ions}\mathrm{Copper}\mathrm{Iron}\mathrm{ions} \end{gathered}$$

In the above reaction, the oxidation number of Iron changes from 0 to +2. Hence, it undergoes oxidation. In contrast, Copper gains two electrons and hence undergoes reduction. Iron is the reducing agent in the reaction and displaces copper from the solution causing the deposition of copper in its elemental form.

Therefore, Iron (Fe) is more reactive than Copper (Cu).