September 22, 2020, 09:57:33 AM
Forum Rules: Read This Before Posting


Topic: [Help] Prove that delta G<= 0 for constant T and P  (Read 2152 times)

0 Members and 1 Guest are viewing this topic.

Offline linkamfai

  • New Member
  • **
  • Posts: 7
  • Mole Snacks: +0/-0
[Help] Prove that delta G<= 0 for constant T and P
« on: June 24, 2015, 06:18:50 AM »
How to prove that Delta G <= 0 for constant T and P processes,

What is the implication of this inequality?

Offline Dan

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 4716
  • Mole Snacks: +467/-72
  • Gender: Male
  • Organic Chemist
    • My research
Re: [Help] Prove that delta G<= 0 for constant T and P
« Reply #1 on: June 24, 2015, 06:26:02 AM »
You must show you have attempted the question, this is a Forum Rule.
My research: Google Scholar and Researchgate

Offline linkamfai

  • New Member
  • **
  • Posts: 7
  • Mole Snacks: +0/-0
Re: [Help] Prove that delta G<= 0 for constant T and P
« Reply #2 on: June 24, 2015, 07:40:18 AM »
G=H-TS
H=U+PV
=> G= U+PV-TS

dG=dU+PdV +VdP - TdS - SdT
=> dU = dq+dw ; dw= dw'-PexdV => w' = non-expansion work
=> dG=dw'(max)

deltaG = w'(max)

but i don't know how to show delta G must <=0 for an isolated system, also the meaning for this inequality

Offline linkamfai

  • New Member
  • **
  • Posts: 7
  • Mole Snacks: +0/-0
entropy and G of fertilied egg
« Reply #3 on: June 24, 2015, 08:34:51 AM »
Consider a fertilized hen egg in and incubator at a constant temperature and pressure environment.

The fertilized egg, hen proteins are formed into a highly ordered chick. Explain why the development of the chick is consistent with the second law. Please include the environment in the discussion.

b) Does the G of the system increase, decrease, or remain the same? How do you know?





ΔSuni=ΔS(sys) + (-ΔHsys/T)
is it because that the process of developing the chick would release heat to the environment?

Offline mjc123

  • Chemist
  • Sr. Member
  • *
  • Posts: 1775
  • Mole Snacks: +252/-11
Re: [Help] Prove that delta G<= 0 for constant T and P
« Reply #4 on: June 24, 2015, 08:49:35 AM »
Consider what you wrote in your other post, about the egg. Can you express that equation slightly differently?

Offline Arkcon

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 7360
  • Mole Snacks: +533/-147
Re: entropy and G of fertilied egg
« Reply #5 on: June 24, 2015, 05:54:21 PM »
What is the definition of each term in the Gibbs free energy equation you've quoted?  Which part of your word problem matches which term in the equation?  Does the development of the chick release heat into the system?  And is that the only thing driving ΔG?
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline Arkcon

  • Retired Staff
  • Sr. Member
  • *
  • Posts: 7360
  • Mole Snacks: +533/-147
Re: [Help] Prove that delta G<= 0 for constant T and P
« Reply #6 on: June 24, 2015, 06:01:20 PM »
Consider what you wrote in your other post, about the egg. Can you express that equation slightly differently?

So why not merge the posts, and let's have all the work together.  So I did. ;D
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Sponsored Links