Change in GIbbs free energy for ethanol

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Discussion Overview

The discussion revolves around calculating the change in Gibbs free energy for a specified mass of ethanol when subjected to an isothermal pressure increase from 1 atm to 3000 atm. The focus is on the application of thermodynamic principles and equations relevant to this calculation.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant presents the equation dG=V(Pf-Pi) for calculating the change in Gibbs energy and attempts to apply it to the problem.
  • Another participant suggests that the equation ΔG=VΔp might be appropriate and emphasizes the need to convert all units into SI units, providing specific conversions for pressure and volume.
  • The first participant expresses frustration with the calculation process and notes a discrepancy between their result and the expected answer of 10.4 kJ.
  • A later reply thanks the second participant for their assistance, indicating that the guidance was helpful in addressing the confusion.
  • One participant reminds others about forum etiquette, suggesting that questions should be posted in a single forum category.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct approach to the calculation, as there are differing equations proposed and a lack of clarity on the correct application of units and conversions.

Contextual Notes

There are unresolved issues regarding unit conversions and the application of the equations for Gibbs free energy, which may affect the accuracy of the calculations presented.

Who May Find This Useful

Students or individuals studying thermodynamics, particularly those interested in Gibbs free energy calculations and related concepts in physical chemistry.

koomanchoo
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hey i seem to be having a lot of trouble with this type of question:
Calculate the change in Gibbs energy of 35g of ethanol (mass density = 0.789g cm-3) when the pressure is increased isothermally from 1 atm to 3000 atm.

in my notes i have that dG=V(Pf-Pi) and search up on the net that mass=volume*density so volume of ethanol comes to 35/.789 the answer is suppose to be 10.4kJ but i get nowhere near it.

dG=(35/.789)*(3000-1) is this the right equation because that's all i can find
pls help me! thanks
P.K
 
Science news on Phys.org
Okay.Maybe

[tex]\Delta G=V\Delta p[/tex]

sounds right.I'm sure you need to convert all units into SI-mKgs.

1 atm=101,325 Pa
1 cm^{3}=10^{-6}m^{3}

1kJ=1000J

Daniel.
 
thanks man

Thanks heeeeeeeeeaps! Daniel :biggrin:
you made my day. spent ages doing that Q like hours and hours just seraching what i was doing wrong. thanks again.
this forum rOcks!
:approve:
 
Please,do not double post.You should have asked it in one single forum.I think Classical Physics was the appropiate choice...

Daniel.
 

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