Which statement correctly contrasts galvanic and electrolytic cells?

• A. Galvanic cells require external energy input to drive the reaction; electrolytic cells are spontaneous and generate electrical energy.
• B. Galvanic cells are spontaneous and convert chemical energy to electrical energy; electrolytic cells require external energy and are non-spontaneous.
• C. Galvanic cells and electrolytic cells are both spontaneous and produce electrical energy.
• D. Galvanic cells are non-spontaneous and require external energy; electrolytic cells are spontaneous and produce electrical energy.

Answer: (B)

The main idea is how spontaneity governs energy flow in these two types of cells. In a galvanic (voltaic) cell, a redox reaction happens on its own because it’s energetically favorable, so chemical energy is directly converted into electrical energy that can do work in the external circuit. That’s why the standard cell potential is positive and the reaction has a negative ΔG. In contrast, an electrolytic cell requires an external energy source to force a non-spontaneous redox reaction to proceed; electrical energy is put into the system to drive the chemical change. Because of this, the roles of the electrodes are opposite to those in a galvanic cell: the anode is positive and the cathode is negative in an electrolytic cell, whereas in a galvanic cell the anode is negative and the cathode is positive. So the statement that galvanic cells are spontaneous and convert chemical energy to electrical energy, while electrolytic cells require external energy input and are non-spontaneous, captures this essential contrast.