Les tables de données fournissent les valeurs de l'enthalpie...

Les tables de données fournissent les valeurs de l'enthalpie molaire de référence et de l'entropie molaire de référence de différentes substances à $25^{\circ} \mathrm{C}$. Comment calculer l'énergie interne d'une substance à partir de son enthalpie?

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Key Concepts

Relationship between Enthalpy and Internal Energy

The relationship between enthalpy and internal energy is given by the equation U = H - pV. This formula allows one to calculate the internal energy by subtracting the pressure-volume work from the enthalpy, which is particularly useful when enthalpy data is available from standard tables.

Internal Energy

Internal energy (U) represents the total energy contained within a system due to both the microscopic kinetic and potential energies of its constituents. It is a state function that does not include the work done by the system in expanding against an external pressure.

Thermodynamic Potentials

Thermodynamic potentials are state functions that provide different ways to account for the energy of a system under various constraints. They allow us to analyze energy changes and phase behavior in processes occurring at constant pressure, volume, or temperature.

Enthalpy

Enthalpy (H) is defined as the sum of the internal energy (U) and the product of pressure and volume (pV) of a system. It is particularly useful when dealing with processes occurring at constant pressure, such as many chemical reactions, and is a key measurement in standard state data tables.

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