Thermodynamics: gas expansion formula or approximation error?

Click For Summary
SUMMARY

This discussion focuses on the calculations involved in reversible gas processes, specifically for CO2 and oxygen under ideal conditions. At 127 °C, 1 L of CO2 is reversibly compressed from 380 mmHg to 1 atm, resulting in heat and work exchanged of Q = L = -34.95 J. Additionally, the maximum work obtainable from 50 L of oxygen expanding isothermally from 100 atm to 50 atm is calculated to be 349,000 J using the formula L = P1 * V1 * ln(P1 / P2). The discussion emphasizes the importance of using consistent units in thermodynamic calculations.

PREREQUISITES
  • Understanding of ideal gas laws and behavior
  • Familiarity with thermodynamic processes, specifically reversible processes
  • Knowledge of logarithmic functions in the context of pressure-volume work
  • Basic proficiency in unit conversions, particularly between atm and mmHg
NEXT STEPS
  • Study the derivation and application of the ideal gas law
  • Learn about isothermal and adiabatic processes in thermodynamics
  • Explore the concept of work done by gases in various thermodynamic cycles
  • Investigate the significance of unit consistency in scientific calculations
USEFUL FOR

Students and professionals in physics and engineering, particularly those specializing in thermodynamics, gas dynamics, and related fields will benefit from this discussion.

lucaud
Messages
1
Reaction score
0
Homework Statement
FIRST TYPE: REVERSIBLE PROCESS


SECOND TYPE: REVERSIBLE PROCESS
Relevant Equations
costant temperature
FIRST TYPE: REVERSIBLE PROCESS At the temperature of 127 ° C, 1 L of CO2 is reversibly compressed from the pressure of 380 mmHg to that of 1 atm. Calculate the heat and labor exchanged assuming the gas is ideal. Q = L = - 34.95 J

CONDUCT 380 mmHg = 0.5 atm L = P1 * V1 * ln (P1 / P2) = 0.5 * 1 * ln (0.5 / 1) = - 0.34 L * atm = -0.34 * 101325/1000 = -35.11 J

SECOND TYPE: REVERSIBLE PROCESS Calculate the maximum work obtainable by making 50 L of oxygen expand isothermally (27 ° C) from 100 atm to 50 atm. Suppose the gas has ideal behavior. 349 * 10 ^ 3 J

PROCESS: L = P1 * V1 * ln (P1 / P2) = 100 * 50 * ln (100/50) = 3465 L * atm = 3465 * 101325/1000 = 351165 J
 
Physics news on Phys.org
Hello @lucaud , welcome !

You need to list the relevant equations you use and mention deviating units if necessary.
In this case the expression for work.

What are the units of pressure in the expression ?
What units did you use in the evaluation ?
 
It seems to me your results are correct. What is your question?
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 6 ·
Replies
6
Views
10K
  • · Replies 1 ·
Replies
1
Views
1K
Replies
8
Views
2K