What distinguishes galvanic and electrolytic cells?

• A. Galvanic cells generate electricity spontaneously; electrolytic cells use electricity to drive non-spontaneous reactions.
• B. Galvanic cells require external energy; electrolytic cells generate electricity.
• C. Both generate electricity spontaneously.
• D. There is no difference.

Answer: (A)

The key idea is what provides the driving force for the reaction. In a galvanic cell, a spontaneous redox reaction occurs, so chemical energy is converted into electrical energy as electrons flow from the anode to the cathode through an external circuit. This makes the cell generate electricity on its own, and the arrangement of electrodes means the anode is negative and the cathode is positive.

In an electrolytic cell, you apply external electrical energy to push a non-spontaneous redox reaction to happen. The external power source forces electrons in the opposite direction to what would occur spontaneously, so the cell consumes electricity to drive the chemical change. Here the anode is connected to the positive terminal and the cathode to the negative terminal, with oxidation at the anode and reduction at the cathode driven by the external voltage.

So, galvanic cells generate electricity from chemical energy because the reaction is spontaneous, while electrolytic cells use electricity to drive a non-spontaneous reaction.