2.2 Equations of State

Equation of state relates \(PVT\) behavior of a component at equilibrium.

The Ideal Gas Law

\[PV = RT \tag*{(4)}\] where \(R\) is universal gas constant; and \(V\) is molar volume; \(T\) is absolute temperature (Kelvin or Rankine).

  • The ideal gas law is a combination of many experimental observations reported by Boyle, Charles, and Gay-Lussac.

  • At constant temperature, a gas obeys: \[P \propto \frac{1}{V}  \tag{Boyle's law}\]

  • At constant pressure, the gas also obeys: \[V \propto T  \tag{Charles' law}\]

  • A fixed volume of gas obeys \[P \propto T \tag{Gay-Lussac's law}\]

  • The ideal gas law forms the basis for much of our study of thermodynamics.

  • Any gas can be considered as ideal under low \(P\) and high \(T\).

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