A mineral ore contains a mixture of compounds of lead and calcium, in approximately equal proportions - VCE - SSCE Chemistry - Question 7 - 2005 - Paper 1

At the positive electrode (anode), the oxidation reaction occurs as follows:

$\text{Pb}^{2+}(aq) + 2e^- \rightarrow \text{Pb}(s)$

At the negative electrode (cathode), the reduction reaction occurs as follows:

$\text{Ca}^{2+}(aq) + 2e^- \rightarrow \text{Ca}(s)$

The new half reaction that may occur at the anode is:

$2\text{H}_2\text{O}(l) \rightarrow 4\text{H}^+(aq) + 4e^- + ext{O}_2(g)$

If copper electrodes were used, the half reaction at the anode could involve the oxidation of copper:

$\text{Cu}(s) \rightarrow \text{Cu}^{2+}(aq) + 2e^-$ This would result in copper ions entering the solution, altering the electrochemical processes occurring in the cell.