For context, I'm in high school. I'm trying to mentally connect electrolysis with the concept of energy changes and kinda having trouble.

I understand the bottom line is that a simple cell converts chemical energy to electrical energy in a spontaneous redox reaction, and in an electrolytic cell, electrical energy is used to cause a non-spontaneous chemical reaction to occur.

I've found resources that vaguely say the overall reaction (?) in a simple cell is exothermic. I find this unclear and confusing.

  • If the reaction is exothermic then the products should have lower energy than the reactants. What are the products and reactants involved in the system, to derive the enthalpy change from?
  • Where did the energy lost go?
  • Don't both bond breaking (oxidation @ anode) and bond making (reduction @ anode) occur? Does the bond making somehow involve more energy? How? (does this have something to do with the cation getting discharged at the cathode being of a less reactive element than the cation formed at the anode? must the electrolyte have a cation that fulfils this requirement?)

For the sake of simplicity assume a simple cell setup with just electrodes, external circuit, and electrolyte. Not connected to a lightbulb or something.

Thank you

  • $\begingroup$ Your second paragraph is exactly correct. But then you wander off a bit. Please search for “Lead-acid battery” in wiki and look at the electrode reactions and net reaction for this extremely common and useful rechargeable battery. Then recharging is electrolysis: input electrical energy results in re-formation of the substances present in the fully charged battery. $\endgroup$ – Ed V Apr 24 at 13:36

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