Abstract
Conventional thermodynamic expression predicts that the isobaric heat capacity decreases with increasing pressure. In model calculations, heat capacity increases with pressure, decreases, or remains insensitive to pressure, depending on the model applied. The expression cannot be applied to the gases, but experimental data on gases show evidently that heat capacity increases with pressure.
Considering the change in enthalpy along two different paths with identical starting and ending points, we derive new expression dC P/dP=αV, where α is the volume coefficient of thermal expansion and V is the molar volume. The expression predicts the increase in C P with pressure and can be applied to gases. The test of the new expression against accurate literature data on the heat capacity of air, gaseous and liquid, demonstrates its validity.
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Drebushchak, V.A. Heat capacity increases with pressure. J Therm Anal Calorim 95, 313–317 (2009). https://doi.org/10.1007/s10973-008-9221-x
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DOI: https://doi.org/10.1007/s10973-008-9221-x