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Absolute entropy of a gas isolated from other phases. This property will be a function of temperature T and pressure p. Reported in units of kJ/mol. All entropies and enthalpies are derived through integration from absolute zero of the heat capacities. Integration constants at phase transition temperatures are included as equation constants.
Please note that the equations below are expressed in terms of heat capacity and not in the necessary integral form.
cp/Rgas = a0 + (a1/T2)×e-a2/T + a3×Y2 + [a4 - a5 /(T - a7)2]×Y8
|Y =||0,||T ≤ a7|
|(T - a7)/(T - a6),||T > a7|
c = ∑aiTi, i ∈ [0, nterms - 1]
where Rgas = universal gas constant
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The TRC Group is part of the Thermophysical Properties Division in NIST's Material Measurement Laboratory
The National Institute of Standards and Technology is an agency of the U.S. Department of Commerce