What is an Equation of State

A relationship between the pressure $P$, the temperature $T$, the volume $V$ and the moles of its components $n$.

If a system is heterogeneous (involving several phases or components) then each phase will have its own equation of state.

Two examples of equation of state are:

The equation of the ideal gas

$PV=nRT$

The equation of van der Waals

$\left( P+\dfrac{an2}{V2} \right)\left(V-nb\right)=nRT$

where $a$ and $b$ are constants different for every gas. Constant $a$ represent a measure of the strength of the intermolecular atraction while $b$ represents the molecular size.

Important comments

• The laws of thermodynamics are so general that cannot be used to determine equations of state for a given system
• Equations of state must be determined experimentally

Any question? Write in the comments and I shall try to help.

Other stuff of interest

• LE01 - AC and DC voltage measurement and continuity test
• LE 02 - Start and stop push button installation 24V DC
• LE 03 - Turn on/off an 24V DC pilot light with a push button
• Minor losses  - Formulas
• What is a process variable?
• What are the most important process variables?
• Time dependence of process variables
• A list of process variables

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Ildebrando.