Thermodynamically favored reaction

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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?
 

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  • #2
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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?
 
  • #3
GCT
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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.
 
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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!
 
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GCT
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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.
 
  • #6
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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.)
 
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GCT
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I somewhat forgot whether it's the negative or positive indicates spontaneity, you'll need to refer to your text to make sure.
 

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