Les tables de données fournissent les valeurs de référence...

Les tables de données fournissent les valeurs de référence de l'enthalpie et de l'entropie de différentes substances à $25^{\circ} \mathrm{C}$.
Calculer la valeur de l'enthalpie et de l'entropie du dioxygène à $110^{\circ} \mathrm{C}$ sous 10 bar.

Key Concepts

Specific Heat Capacity and Integration

The specific heat capacity at constant pressure (cp) is vital for calculating changes in state functions like enthalpy and entropy. By integrating cp with respect to temperature (and cp/T for entropy), one can determine the adjustments needed to translate properties from a known reference condition to any other temperature, reflecting the energy absorbed and the corresponding change in disorder.

Reference State and Correction

Reference states provide standard values of thermodynamic properties at set conditions, such as 25°C. To calculate the properties at other conditions, corrections are made by integrating the substance’s specific heat capacities over the temperature change and by including adjustments for pressure, ensuring that the state function properties are correctly evaluated at the new state.

Enthalpy

Enthalpy is a state function representing the total heat content of a system. In thermodynamics, when the enthalpy at a different temperature is sought, one typically integrates the substance’s specific heat capacity at constant pressure from a reference temperature to the new temperature, thereby accounting for the added thermal energy.

Entropy

Entropy is a measure of the system’s disorder or randomness and is also a state function. To determine the entropy change when the temperature or pressure varies, it is necessary to integrate the specific heat capacity over temperature (dividing by temperature) in addition to applying any logarithmic corrections for pressure changes, following the principles of statistical mechanics and ideal gas behavior.

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