Max inversion temperature for a gas (Dieterici’s equation of state)

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Homework Help Overview

The discussion revolves around the concept of the maximum inversion temperature for a gas as described by Dieterici’s equation of state. Participants are exploring the relationship between temperature, pressure, and molar volume in the context of the inversion curve.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants are attempting to derive the maximum temperature by setting pressure to zero in the inversion curve formula. Questions arise regarding the correct interpretation of the inversion curve and the relationship between temperature and molar volume versus pressure.

Discussion Status

Some participants have provided feedback on the correctness of the original poster's work. There is a recognition of the need to eliminate variables between equations, and guidance has been offered on how to approach the problem by substituting expressions for volume.

Contextual Notes

Participants are discussing the implications of using Dieterici’s equation of state and the specific forms of the equations provided by the lecturer. There is an acknowledgment of the need for explicit expressions for temperature or volume to proceed with the calculations.

jonny997
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Homework Statement
I’m trying to calculate the maximum inversion temperature from the inversion curve.
Relevant Equations
See below
DE470E58-1630-423E-84E8-0E5DBCBDA631.jpeg

The notes my lecturer has provided state that the maximum temperature can be found taking p = 0 in the inversion curve formula, given as:

6A8750D7-F98E-47B3-B21A-22DFC4A35C64.jpeg


I’m not sure how to obtain this??

These are the formulas:
01F6BEEB-B15E-431E-863B-EB4FA8D37442.jpeg

This is my attempt at a solution :
D4A3A282-5D6B-48D9-88E7-19D674F87E42.jpeg

BA25810D-9D85-40B6-A08C-CF6AB4E45C1B.jpeg

Not sure if this approach is right?
 
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Your work looks correct to me.

For part (b) you obtain the inversion curve as a relation between the inversion temperature ##T## and the molar volume ##V##:

1713569406810.png


I believe an inversion curve is typically a relation between ##T## and ##P## rather than between ##T## and ##V##.
 
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TSny said:
Your work looks correct to me.

For part (b) you obtain the inversion curve as a relation between the inversion temperature ##T## and the molar volume ##V##:

View attachment 343722

I believe an inversion curve is typically a relation between ##T## and ##P## rather than between ##T## and ##V##.
Hey. Thanks for the response. Do you have any idea how I would go about obtaining the expression my lecturer has provided? Namely, $$ P_{inv} = \left[\frac{2a}{b^2} - \frac{RT}{b}\right]e^{\frac{1}{2}-\frac{a}{RTb}}$$ If I am to rewrite ## T = \frac{2a}{R}\left(\frac{1-\frac{b}{V}}{b}\right) ## in terms of ##P## do I not need an explicit expression for T or V from Dieterici’s e.o.s.
 
jonny997 said:
If I am to rewrite ## T = \frac{2a}{R}\left(\frac{1-\frac{b}{V}}{b}\right) ## in terms of ##P## do I not need an explicit expression for T or V from Dieterici’s e.o.s.
You need to eliminate ##V## between the equation of state and the equation ## T = \frac{2a}{R}\left(\frac{1-\frac{b}{V}}{b}\right) ##. Decide which equation is easier to solve for ##V## and then substitute for ##V## in the other equation.
 
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TSny said:
You need to eliminate ##V## between the equation of state and the equation ## T = \frac{2a}{R}\left(\frac{1-\frac{b}{V}}{b}\right) ##. Decide which equation is easier to solve for ##V## and then substitute for ##V## in the other equation.
Ahhh okay, thank you. For some reason it didn’t click that I could solve for V using ## T = \frac{2a}{R}\left(\frac{1-\frac{b}{V}}{b}\right) ## and then sub that into the other equation 😬 I’ve got it now
 
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