What is the function of the cathode in an electrolytic cell ?

1 Answer
Dec 30, 2014

The cathode is where reduction occurs in an electrolytic cell.

Explanation:

Product on a cathode from www.bbc.co.uk

(BBC )

In the case of copper(II) chloride solution the +ve copper(II) ions are attracted to the cathode and discharged.

The numeral (II) tells us that the copper ion has a 2+ charge so will require 2 moles of electrons to form a neutral copper atom.

The half equation will therefore be:

#Cu_((aq))^(2+)+2erarrCu_((s))#

So the charge on the ion decides how many moles of electrons are needed. E.g aluminium is extracted from its ore by the electrolysis of molten alumina. The half equation is:

#Al_((l))^(3+)+3erarrAl_((l))#

In some cases for aqueous solutions, too much energy is required to discharge the metal ion. In the case of aqueous sodium chloride water is reduced instead:

#H_2O_((l))+erarr(1)/(2)H_(2(g))+OH_((aq))^-#

This process forms the basis of the chlor - alkali industry.