Berthelot equation of state: Difference between revisions

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At the [[critical points | critical point]] one has <math>\left.\frac{\partial p}{\partial v}\right|_{T=T_c}=0 </math>, and <math>\left.\frac{\partial^2 p}{\partial v^2}\right|_{T=T_c}=0 </math>,  
At the [[critical points | critical point]] one has <math>\left.\frac{\partial p}{\partial v}\right|_{T=T_c}=0 </math>, and <math>\left.\frac{\partial^2 p}{\partial v^2}\right|_{T=T_c}=0 </math>,  


which leads to (Eqs. 4.1 - 4.3 <ref>[http://dx.doi.org/10.1021/ed039p464 Antony F. Saturno "Daniel Berthelot's equation of state", Journal of Chemical Education '''39''' (9) pp. 464-465 (1962)]</ref><ref>  [http://www.ucm.es/info/molecsim/Berthelot_EOS.sws SAGE Notebook Worksheet] for use in the mathematics program [http://www.sagemath.org/ SAGE]</ref>)
which leads to (Eqs. 4.1 - 4.3 <ref>[http://dx.doi.org/10.1021/ed039p464 Antony F. Saturno "Daniel Berthelot's equation of state", Journal of Chemical Education '''39''' (9) pp. 464-465 (1962)]</ref><ref>  [http://www.ucm.es/info/molecsim/Berthelot_EOS.sws SAGE Notebook Worksheet] for use in the open-source mathematics software [http://www.sagemath.org/ SAGE]</ref>)




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:<math>b= \frac{v_c}{3}</math>
:<math>b= \frac{v_c}{3}</math>


and
and giving a critical [[compressibility factor]] of


:<math>\frac{RT_c}{p_cv_c} = \frac{8}{3} \approx 2.667 </math>  
 
:<math>Z_c = \frac{p_cv_c}{RT_c} = \frac{3}{8} = 0.375 </math>  




where <math>p</math> is the [[pressure]], <math>T</math> is the [[temperature]] and <math>R</math> is the [[molar gas constant]]. <math>T_c</math> is the [[critical points | critical]] temperature, <math>p_c</math> is the pressure and <math>v_c</math> is the volume at the critical point.
where <math>p</math> is the [[pressure]], <math>T</math> is the [[temperature]] and <math>R</math> is the [[molar gas constant]]. <math>T_c</math> is the [[critical points | critical]] temperature, <math>p_c</math> is the pressure and <math>v_c</math> is the volume at the critical point.
==Low pressure variant==
Berthelot also proposed an [[Equations of state |equation of state]] for use at low pressures{{reference needed}}:
:<math>p = \frac{RT}{v} \left( 1 + \frac{9}{128} \frac{pT_c}{p_c T} \left( 1- \frac{6T_c^2}{T^2} \right)  \right)</math>
==References==
==References==
<references/>
<references/>
[[category: equations of state]]
[[category: equations of state]]

Latest revision as of 15:31, 8 January 2014

The Berthelot equation of state [1][2] can be written as

.

At the critical point one has , and ,

which leads to (Eqs. 4.1 - 4.3 [3][4])



and giving a critical compressibility factor of



where is the pressure, is the temperature and is the molar gas constant. is the critical temperature, is the pressure and is the volume at the critical point.

Low pressure variant[edit]

Berthelot also proposed an equation of state for use at low pressures[?]


References[edit]