Need help with balancing half-reactions ??

Question

Consider a galvanic cell in which Al^3+ is reduced to elemental aluminum and magnesium metal is oxidized to Mg^2+. Write the balanced half-cell reactions that take place at the cathode and at the anode.

Half-Cell Reaction at the Cathode:

Half-Cell Reaction at the Anode:

Answer 1

Reduction takes place at the cathode:

Al³⁺(aq) + 3e- ==> Al(s)

Oxidation takes place at the anode:

Mg(s) ==> Mg²⁺(aq) + 2e-

In order to equalize electrons being transferred, multiply reduction by 2 and oxidation by 3 to get:

Cathode reaction:

2Al³⁺(aq) + 6e- ==> 2Al(s)

Anode reaction:

3Mg(s) ==> 3Mg²⁺(aq) + 6e-