Thermodynamically favored reaction

nipwoni

I have a homework question about the electrolysis of seawater, and I need to know what reactions are thermodynamically favored. One reaction is the production of H2 and O2, and it has a standard cell potential of -2.06 V. The other is the production of H2 and Cl2, and has a standard cell potential of -2.19 V. Is the favored reaction the one that occurs at a more negative voltage, or the one at a voltage with a smaller absolute value?

so-crates

What does it mean for a reaction to be "thermodynamically favored"? What is the name of the quantity that measures this ? How does that quantity relate to the variables you have in an electrochemical cell?

GCT

The production of hydrogen and oxygen from water is not favored thermodynamically so you can guess upon the productino of hydrogen and chlorine gas based on this.

nipwoni

But based on the voltages which will be favored over the other? I know that reactions at "lower" voltage/ cell potential are favored, but what do they mean by lower? Is it the one with an actual lower number (more negative) or the one with a voltage closer to zero? I need to know for an exam tomorrow, not just for these particular reactions. Thanks!

GCT

Doesn't your text say answer explicitly on these matters? I gave you hints in my post, and you should be able to figure it out.

nipwoni

Ok so it's the more negative voltage that's favored.
My book didn't say, and my problem was that I got conflicting answers from different TAs. The answer sheet to the problem set also contradicts what you said, but they're wrong sometimes (quite often actually.)

GCT

I somewhat forgot whether it's the negative or positive indicates spontaneity, you'll need to refer to your text to make sure.