Calculating Change in Entropy for Gas Mix

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SUMMARY

The discussion centers on calculating the change in entropy for a gas mixture involving monatomic helium (He) at 113 K and diatomic nitrogen (N2) at 298 K, both at a pressure of 1,000,000 Pa in containers of 0.1 m³. The entropy change due to increased volume is calculated using the formula: change in entropy = Number of particles * ln(Volume final/Volume initial), yielding a result of 6.126026862e25 for helium. The discussion also raises questions about calculating entropy changes due to temperature variations and the total entropy change, as well as the standard entropy change during the mixing process.

PREREQUISITES
  • Understanding of thermodynamics principles, particularly entropy.
  • Familiarity with the ideal gas law (PV = nkt).
  • Knowledge of statistical mechanics, specifically the concept of microstates (omega).
  • Ability to perform logarithmic calculations and manipulate scientific notation.
NEXT STEPS
  • Learn how to calculate the change in entropy due to temperature changes in gas mixtures.
  • Study the concept of thermal equilibrium and its effect on gas mixtures.
  • Explore the derivation and application of the standard entropy change in thermodynamic processes.
  • Investigate advanced statistical mechanics concepts related to microstates and entropy calculations.
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Students and professionals in thermodynamics, chemical engineering, and physical chemistry, particularly those working with gas mixtures and entropy calculations.

ajbeach2
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Take two containers, each with volume 0.1 m3, containing ideal gases of monatomic He at T= 113 K and diatomic N2 at T = 298 K, respectively. Each gas is at pressure p= 1000000 Pa. A valve is opened allowing these two gases to mix. They are kept thermally isolated from the outside.

1) Now we want to calculate the change in entropy during this process. What is the change of dimensionless entropy solely due to the fact that the gases have more volume accessible?


2). What is the change of dimensionless entropy solely due to the fact that the gases' temperatures have changed?


3) What is then the total change of dimensionless entropy?


4) What is the change of the standard entropy in this process?



Equations: PV = nkt
Entroy = ln(omega)
omega = total number of microstates
k = 1.381e-23

change in entropy = Number of particles * ln(Volume final/volume initial)




i calculated the number of particles for gas A as 6.408079306e25 and for B 2.429909267e25

i used this in the change in entropy equations which relates the change in entropy to the number of particles times the ln of the change in volume. For the first question i got
6.126026862e25 which is right. I don't know how to calculate parts 2,3 or 4
 
Last edited:
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8 years later, and I'm struggling with the exact same problem.
 
Albert11317 said:
8 years later, and I'm struggling with the exact same problem.
If you let the two gases thermally equilibrate with one another, what would the final temperature be?
 

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