why is it that aluminium metal cannot be obtained by the electrolysis of an aqueous solution of a salt of aluminium?
why is it that aluminium metal cannot be obtained by the electrolysis of an aqueous solution of a salt of aluminium?
When we are considering the electrolysis of an aqueous solution of Al3+ salts, the different species that would be present in the aqueous solution are Al3+ ion, anion of the aluminum salt and H2O. At cathode, the following two reactions are possible
2 H2O + 2e- →H2 (g) + 2OH-(aq) E0 = -0.83V (1)
Al3+ + 3e- → Al (s) E0 = -1.66V (2)
The reduction potential of Aluminium is lower than that of water. This means that it has lesser tendency to get reduced than water. The reaction with a higher reduction potential will occur at the cathode and since water has higher reduction potential, therefore reaction (1) will occur at the cathode. Hence the electrolysis of Aluminium salt will give Hydrogen instead of aluminium.
When we are considering the electrolysis of an aqueous solution of Al3+ salts, the different species that would be present in the aqueous solution are Al3+ ion, anion of the aluminum salt and H2O. At cathode, the following two reactions are possible
2 H2O + 2e- →H2 (g) + 2OH-(aq) E0 = -0.83V (1)
Al3+ + 3e- → Al (s) E0 = -1.66V (2)
The reduction potential of Aluminium is lower than that of water. This means that it has lesser tendency to get reduced than water. The reaction with a higher reduction potential will occur at the cathode and since water has higher reduction potential, therefore reaction (1) will occur at the cathode. Hence the electrolysis of Aluminium salt will give Hydrogen instead of aluminium.
