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

  • #1
jonny997
20
5
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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  • #2
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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  • #3
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.
 
  • #4
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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  • #5
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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FAQ: Max inversion temperature for a gas (Dieterici’s equation of state)

What is the Max inversion temperature in the context of Dieterici's equation of state?

The Max inversion temperature refers to the highest temperature at which a gas can exhibit a phase transition from a gas to a liquid when compressed. In the context of Dieterici's equation of state, it is the temperature above which the gas cannot be liquefied, regardless of the pressure applied.

How does Dieterici's equation differ from other equations of state?

Dieterici's equation of state incorporates the effects of molecular attraction and volume exclusion, making it more accurate for real gases compared to the ideal gas law. It includes an exponential term that accounts for the attractive forces between molecules, which is significant at high pressures and low temperatures.

What is the significance of the Max inversion temperature in practical applications?

The Max inversion temperature is crucial for understanding the behavior of gases in industrial processes, such as gas liquefaction and refrigeration. It helps engineers and scientists determine the conditions necessary to achieve phase changes and optimize processes involving gas storage and transport.

How can the Max inversion temperature be calculated using Dieterici's equation?

The Max inversion temperature can be determined by analyzing the critical constants of the gas and applying them in Dieterici's equation. The equation can be manipulated to find the temperature at which the compressibility factor changes behavior, indicating the onset of liquefaction.

Are there any limitations to using Dieterici's equation for determining the Max inversion temperature?

Yes, while Dieterici's equation provides a better approximation for real gases than the ideal gas law, it may still have limitations at very high pressures or for gases with strong intermolecular forces. Additionally, it may not accurately predict behavior for all types of gases, particularly those that deviate significantly from ideal behavior.

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