Thermodynamically favored reaction

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Discussion Overview

The discussion revolves around the thermodynamic favorability of reactions during the electrolysis of seawater, specifically comparing the production of hydrogen and oxygen versus hydrogen and chlorine. Participants explore the implications of standard cell potentials and their relationship to thermodynamic favorability.

Discussion Character

  • Homework-related
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant questions which reaction is thermodynamically favored based on their standard cell potentials of -2.06 V for H2 and O2 and -2.19 V for H2 and Cl2.
  • Another participant seeks clarification on what it means for a reaction to be "thermodynamically favored" and asks about the relevant quantities that measure this in an electrochemical cell.
  • A participant asserts that the production of hydrogen and oxygen is not favored thermodynamically, suggesting that hydrogen and chlorine gas is the more likely product.
  • There is confusion regarding whether a lower voltage (more negative) or a voltage closer to zero indicates a favored reaction, with one participant emphasizing the need for clarity before an upcoming exam.
  • One participant suggests that the textbook should provide explicit answers to these questions, while another mentions conflicting information from different teaching assistants and the answer sheet.
  • A later reply indicates uncertainty about whether negative or positive voltages indicate spontaneity, advising to refer back to the text for confirmation.

Areas of Agreement / Disagreement

Participants express differing views on which reaction is thermodynamically favored and the interpretation of standard cell potentials. There is no consensus on the correct understanding of the relationship between voltage and thermodynamic favorability.

Contextual Notes

Participants reference various sources, including textbooks and teaching assistants, which may contain conflicting information. The discussion highlights the need for clarity on definitions and the implications of standard cell potentials in electrochemical reactions.

nipwoni
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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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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?
 
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.
 
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!
 
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.
 
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.)
 
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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