Title: isosteric enthalpy of adsorption
Long Title: IUPAC Gold Book - isosteric enthalpy of adsorption
DOI: 10.1351/goldbook.I03313
Status: current

Definition
When the addition of the differential amount of component \(i\) \(\mathrm{d}n_{i}^{\sigma }\) or \(\mathrm{d}n_{i}^{\rm{s}}\) is effected at constant pressure \(p\), the differential molar enthalpy of adsorption, \(\Delta _{a}H_{i}^{\sigma}\) or \(\Delta _{a}H_{i}^{\rm{s}}\) also called the isosteric enthalpy of adsorption (\(q^{\rm{st}}\)) is defined as: \[\Delta _{a}H_{i}^{\sigma} = -q^{\rm{st},\sigma} = U_{i}^{\sigma} - H_{i}^{\rm{g}}\] \[\Delta _{a}H_{i}^{\rm{s}} = -q^{\rm{st},\sigma} = H_{i}^{\sigma} - H_{i}^{\rm{g}}\] where \(H_{i}^{\rm{s}}=(\frac{\partial H^{\rm{s}}}{\partial n_{i}^{\rm{s}}})_{T,p,m,n_{j}^{\rm{s}}}\) and \(H_{i}^{\rm{g}}\) is the partial molar enthalpy of component \(i\) in the gas phase, i.e. \((\frac{\partial H^{\rm{g}}}{\partial n_{i}^{\rm{g}}})_{T,p,n_{i}^{\rm{g}}}\)

Related Term
- enthalpy: https://goldbook.iupac.org//terms/view/E02141

Source
- PAC, 1972, 31, 577. 'Manual of Symbols and Terminology for Physicochemical Quantities and Units, Appendix II: Definitions, Terminology and Symbols in Colloid and Surface Chemistry' on page 603 (https://doi.org/10.1351/pac197231040577)

Other Outputs
- html: https://goldbook.iupac.org/terms/view/I03313/html
- json: https://goldbook.iupac.org/terms/view/I03313/json
- xml: https://goldbook.iupac.org/terms/view/I03313/xml

Citation: Citation: 'isosteric enthalpy of adsorption' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351/goldbook.I03313
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Accessed: 2026-06-12T04:39:33+00:00