A galvanic cell is prepared with solutions of Mg²⁺ (aq) with a Mg (s) electrode and Al³⁺ (aq) with an Al (s) electrode separated by a salt bridge. What is the purpose of the salt bridge in this galvanic cell?
1) To complete the circuit and allow the flow of electrons
2) To prevent the mixing of the two solutions
3) To increase the rate of the redox reaction
4) To balance the charges in the cell