Galvanic cells always involve spontanous oxidation-reduction reactions. In any electrochemical cell, the electrons always move from anode to cathode. Also, the anode is always the site of oxidation, and the cathode is always the site of reduction. Since the reaction is spontaneous (net release of free energy) it drives the movement of electrons from the anode to the cathode. Remember, oxidation is loss of electrons and reduction is gain of electrons. Since oxidation always occurs at the anode, we are left with an excess of electrons, making it the negative electrode. It should makes sense that the extra electrons from the anode spontaneously travel to the cathode (positive electrode).

To help remember oxidation-reduction processes, consider the mnemonics "OIL RIG" and "An Ox, Red Cat." OIL RIG stands for "oxidation is loss, reduction is gain" in reference to electrons. An Ox, Red Cat tells us that the anode is the site of oxidation, while the cathode is the site of reduction.

Electrolytic cells use non-spontaneous reactions that require an external power source in order to proceed. The values between galvanic and electrolytic cells are opposite of one another. Galvanic cells have positive voltage potentials, while electrolytic voltage potentials are negative. Both types of cell, however, have oxidation occur at the cathode and reduction occur at the anode.

First we must rearrange the reduction potentials so that when added together, they match the reaction that takes place in the electrochemical cell.

In the overall reaction,  is in the reactant side, so the  equation must be inverted.

Use the equation:  to find the . 

 is product, while  is the reactant.

The cell must be galvanic because the  value is positive. This means, this the reaction is a spontaneous reaction occurs without an outside energy source.

Oxidation always takes place at the anode, regardless of the electrical cell type. The charges on the anode and cathode are reversed between galvanic and electrolytic cells. In electrolytic cells, the cathodes are marked negative and the anodes are marked positive. In galvanic cells, the reverse is true: cathodes are marked positive and anodes are marked negative.

Reduction always occurs at the cathode, and oxidation always occurs at the anode. Since reduction is the addition of electrons, electrons must travel toward the site of reduction.

In an electrolytic cell the negative charge is on the cathode, while the positive charge is on the anode. Since an electrolytic cell requires energy to perpetuate the reaction, we are pushing the electrons against their potential gradient. The electrons, which are negatively charged, are traveling towards the cathode, which is also negatively charged.

Since our overall reaction includes magnesium solid in the reactants, we must invert the first equation, including the sign of the electrical potential.

This cell is galvanic because the electrical potential, , is positive. Galvanic cells involve spontaneous reactions, and therefore, do not need any external energy source to drive the reaction.

Since our overall reaction includes calcium solid in the reactants, we must invert the second equation, including the sign of the electrical potential.

This cell is electrolytic because the electrical potential, , is negative. Electrolytic cells involve nonspontaneous reactions, and therefore, must have an external voltage source such as a battery to drive their reactions.

Using the equation: , for a spontaneous reaction to occur,  must be positive. With solid zinc as the reactant, any other solid can act as the product, and still give a positive . This is because, subtracting a negative number will give a positive value.

As a result, the equation,, will become inverted to make the solid zinc a reactant. . Solid zinc will give electrons, and oxidize, to reduce other ions. 

First we must rearrange the reduction potentials so that when added together, they match the reaction that takes place in the electrochemical cell.

In the overall reaction,  is in the reactant side, so the  equation must be inverted.

Use the equation:  to find the . 

 is product, while  is the reactant.

The cell must be electrolytic because the  value is negative. This means, this the reaction is a non-spontaneous reaction and need a applied energy source to make the reaction take place.

Oxidation always takes place at the anode, regardless of the electrical cell type. The charges on the anode and cathode are reversed between galvanic and electrolytic cells. In electrolytic cells, the cathodes are marked negative and the anodes are marked positive. In galvanic cells, the reverse is true: cathodes are marked positive and anodes are marked negative.