Critical variable - Alchetron, The Free Social Encyclopedia

Critical variables are defined, for example in thermodynamics, in terms of the values of variables at the critical point.

On a PV diagram, the critical point is an inflection point. Thus:

( ∂ P ∂ V ) C = 0 ( ∂ 2 P ∂ V 2 ) C = 0

For the van der Waals equation, the above yields:

P C = a 27 b 2 V C = 3 n b T C = 8 a 27 b R

References

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