Understanding Van der Waals Equation for Ideal and Actual Gases | Homework Help

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Discussion Overview

The discussion revolves around the Van der Waals equation for real gases and its relation to the ideal gas law. Participants are exploring the corrections made in the Van der Waals equation and how they relate to the behavior of gases under different conditions, focusing on the implications of volume and pressure corrections.

Discussion Character

  • Homework-related
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant questions whether the Van der Waals equation represents ideal pressure and volume in terms of measured values, suggesting that PV=nRT applies to ideal conditions.
  • Another participant counters that this is an approximation and not strictly correct, indicating that the Van der Waals equation provides a better model than the ideal gas equation.
  • There is a discussion about the term V-nb, with one participant asserting that it represents the actual volume available to gas molecules, while another explains that it accounts for the volume occupied by gas particles.
  • One participant summarizes their understanding of the corrections in the Van der Waals equation, stating that V-nb considers the volume of particles and that the pressure correction accounts for intermolecular forces.

Areas of Agreement / Disagreement

Participants express differing views on the interpretation of the Van der Waals equation and its corrections. Some agree on the need for corrections in real gas behavior, while others challenge the clarity and implications of these corrections. The discussion remains unresolved regarding the precise nature of these corrections and their interpretations.

Contextual Notes

Participants have not fully clarified the assumptions underlying the corrections in the Van der Waals equation, nor have they resolved the implications of these corrections on the ideal gas law.

babita
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Homework Statement



(P+ an^2/V^2)(V-nb) = nRT
I'm having some problems in understanding the above equation.

firstly, PV=nRT holds for ideal P and V , so after correction we are writing ideal P and V in terms of measured P and V right?

secondly V-nb is the actual volume not the ideal one. isn't it? if yes what is it doing in the above equation?

Homework Equations





The Attempt at a Solution

 
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please reply...i'm going mad:mad::mad:
 
babita said:

Homework Statement



(P+ an^2/V^2)(V-nb) = nRT
I'm having some problems in understanding the above equation.

firstly, PV=nRT holds for ideal P and V , so after correction we are writing ideal P and V in terms of measured P and V right?
No. This is an approximation that is somewhat better than the simple form of the IGE.
secondly V-nb is the actual volume not the ideal one. isn't it? if yes what is it doing in the above equation?
V-nb is a correction to the volume that is proportional to the number of moles of gas and has units of volume. Recall that the IGE assumes that gas molecules/atoms are non-interacting and have no "size".
 
okkk...i was unable to understand the corrections made by van der waals in IGE...would u pls check if I'm getting it right...

in PV=nRT V is the volume that is available to the gas molecules, since at ideal gas conditions(high T and low P) the volume of particles is negligible,we can write the volume as V only...but in other cases we write V-nb taking into account the volume of particles too.
and in PV=nRT P stands for the pressure that gas particles would exert if no inter molecular forces were present...so in ideal conditions this is approximately equal to measured P...in other cases we have to add an^2/V^2
thankyou
 

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