Arrange the following metals in the order in which they displace each other from the solution of their salts.
Al, Cu, Fe, Mg and Zn.

${{\mathrm{E}}^{\mathrm{o}}}_{{\mathrm{Al}}^{3+}/\mathrm{Al}}=-1.66 \mathrm{V};{{\mathrm{E}}^{\mathrm{o}}}_{{\mathrm{Cu}}^{2+}/\mathrm{Cu}}=+0.34 \mathrm{V}$

${{\mathrm{E}}^{\mathrm{o}}}_{{\mathrm{Fe}}^{2+}/\mathrm{Fe}}=-0.44 \mathrm{V};{{\mathrm{E}}^{\mathrm{o}}}_{{\mathrm{Mg}}^{2+}/\mathrm{Mg}}=-2.36 \mathrm{V}$

$\text{ and }{{\mathrm{E}}^{\mathrm{o}}}_{{\mathrm{Zn}}^{2+}/\mathrm{Zn}}=-0.76 \mathrm{V}$

A metal with more negative.value of ${{\mathrm{E}}^{\mathrm{o}}}_{\text{red }}$ is a stronger reducing agent than those which have less negative or positive value of ${{\mathrm{E}}^{\mathrm{o}}}_{\text{red }}$. Therefore, Mg can displace all the given metals from their aqueous salt solutions.
Al can displace all metals except Mg from their aqueous salt solutions. Zinc can displace Fe and Cu from their aqueous salt solutions and Fe can only displace Cu from its aqueous salt solution. Hence, the order in which they can displace each other from the solution of their salts is as follows:
Mg, Al, Zn, Fe, Cu