Re: Van der vals eqn of state help!

From: Joshua Halpern (vze23qvd_at_verizon.net)
Date: 01/29/05 

Date: Sat, 29 Jan 2005 04:25:23 GMT

Ian Gay wrote:
> josephsch@gmail.com (Joseph) wrote in
> news:56f59da.0501281710.4410bcc3@posting.google.com:
>
>
>>Hi guys I was just trying to figure out the following question, and
>>was wondering if anyone knows the answers.
>>
>>If we say (V^2P+a)(V-b)=RTV^2. The point where all three roots of
>
> the
>
>>cubic equation are equal defines the Van der Waals Critical Point
>
> for
>
>>the gas. Derive the equations that predict Tcrit , Vcrit and Pcrit
>>given values of a, b and R ?
>>
>>any help would be appreciated!
>>
>
>
> Phys Chem textbook. Or complain to your prof that it's not really an
> interesting problem.
>
I'll give you a hint. Solve for P, take the first and second
derivatives of p wrt V and set them equal to zero (The critical
temperature is a point of inflection). Solve for P,V and T crit.

josh halpern