Question

Why are voltage-producing voltaic cell reactions spontaneous but electrolysis reactions nonspontaneous?

Answer 1

A voltaic cell creates a spontaneous flow of e- from the anode to cathode due to a difference in Reduction potential. an electrolytic cell applies an external voltage to force the flow against this gradient.

Explanation:

electrons will spontaneously flow to the electrode of the cell with the greatest reduction potential - voltaic cells use this potential energy to generate a spontaneous flow of electrons from the anode (lower reduction potential) to the cathode (higher reduction potential), whereas electrolysis applies a voltage (an external source of electron flow that exceeds the force spontaneous flow of the electrolytic cell) to force the electrons to travel towards the region with lower reduction potential.