Heat capacity and thermodynamics of solid and liquid pyridine-3-carboxylic acid (nicotinic acid) over the temperature range 296K to 531K
| Autor: | Manuel E. Minas da Piedade, Abhinav Joseph, Carlos E. S. Bernardes |
|---|---|
| Rok vydání: | 2012 |
| Předmět: |
Isothermal microcalorimetry
chemistry.chemical_classification Phase transition Carboxylic acid Thermodynamics Atmospheric temperature range Heat capacity Atomic and Molecular Physics and Optics Gibbs free energy chemistry.chemical_compound symbols.namesake Differential scanning calorimetry chemistry Pyridine symbols General Materials Science Physical and Theoretical Chemistry |
| Zdroj: | The Journal of Chemical Thermodynamics. 55:23-28 |
| ISSN: | 0021-9614 |
| Popis: | The molar heat capacity of pyridine-3-carboxylic acid (nicotinic acid) for T = (296 to 531) K was investigated by differential scanning calorimetry (DSC) and Calvet-drop microcalorimetry. The measurements extended up to the liquid range and also covered the interval where a reversible and fast solid-solid (cr II → cr I) phase transition occurs. The molar enthalpies and entropies of that phase transition and of fusion were obtained as T trs = (455.0 ± 0.2) K, Δ trs H m o = (0.90 ± 0.10) kJ ⋅ mol −1 , Δ trs S m o = (1.98 ± 0.22) J ⋅ K −1 ⋅ mol −1 , T fus = (509.91 ± 0.04) K, Δ fus H m o = (28.2 ± 0.1) kJ ⋅ mol −1 , and Δ fus S m o = (55.30 ± 0.16) J ⋅ K −1 ⋅ mol −1 . By combining these experimental results with the previously reported Δ sub H m (NA,cr II) at T = 366.5 K, the corresponding entropy in the gaseous state calculated at the B3LYP/6-31+G(d,p) level of theory, and Δ f H m o (NA),cr II) at T = 298.15 K, it was possible to estimate the standard molar Gibbs energy of formation functions necessary for the construction of the Δ f G m ∘ vs. T diagram illustrating the enantiotropic nature of this system. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect