Search our Thermodynamic Data Tables by entering a substance name, filtering by physical state or element group, and pull up the standard enthalpy of formation (ΔH°f), Gibbs free energy (ΔG°f), and standard entropy (S°) for any compound you need.
Substance
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ΔH°f (kJ/mol)
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ΔG°f (kJ/mol)
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S° (J/mol·K)
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State
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Standard thermodynamic properties are measured at standard conditions (298K, 1 bar pressure). They include enthalpy of formation (ΔH°f), Gibbs free energy of formation (ΔG°f), and standard entropy (S°).
ΔH°f is the standard enthalpy of formation - energy change when forming one mole of compound from elements. ΔG°f is the standard Gibbs free energy of formation - useful work obtainable from the formation reaction.
By convention, the standard enthalpy and Gibbs energy of formation are zero for pure elements in their most stable form at 298K (like O2 gas, C graphite, Na solid).
Values are compiled from NIST databases and peer-reviewed literature. Accuracy typically ranges from ±0.1 to ±5 kJ/mol depending on the substance and measurement methods used.
These are standard values at 298K. For other temperatures, you need temperature-dependent heat capacity data and integration formulas to calculate properties at different conditions.
These indicate physical states: (s) solid, (l) liquid, (g) gas, and (aq) aqueous solution. The same compound can have different thermodynamic properties in different states.
Use Hess's law: ΔH°reaction = Σ(ΔH°f products) - Σ(ΔH°f reactants). Sum the formation enthalpies of products minus reactants, accounting for stoichiometric coefficients.
Standard SI units: kJ/mol for enthalpy and Gibbs energy values, and J/mol·K for entropy values. All data is referenced to 298.15K and 1 bar pressure.