Internally consistent thermodynamic data for magnesium sulfate hydrates
2009; Elsevier BV; Volume: 73; Issue: 22 Linguagem: Inglês
10.1016/j.gca.2009.08.005
ISSN1872-9533
AutoresKlaus-Dieter Grevel, Juraj Majzlan,
Tópico(s)CO2 Sequestration and Geologic Interactions
ResumoExperimental studies on the stability of several Mg-sulfate hydrates including epsomite (MgSO4·7H2O), hexahydrite (MgSO4·6H2O), starkeyite (MgSO4·4H2O), and kieserite (MgSO4·H2O) as a function of temperature and relative humidity are in poor agreement with calculations based on thermodynamic properties of these substances taken from the literature. Therefore, we synthesized four different MgSO4 hydrates and measured their enthalpies of formation by solution calorimetry at T = 298.15 K. The resulting enthalpies of formation from the elements are: ΔfH0298 (epsomite) = −3387.7 ± 1.3 kJmol−1 ΔfH0298 (hexahydrite) = −3088.1 ± 1.1 kJmol−1 ΔfH0298 (sanderite, MgSO4·2H2O) = −1894.9 ± 1.3 kJmol−1 ΔfH0298 (kieserite) = −1612.4 ± 1.3 kJmol−1 Epsomite: ΔfH0298 = −3388.7 kJmol−1, S0298 = 371.3 Jmol−1 K−1, ΔfG0298 = −2871.0 kJmol−1 Hexahydrite: ΔfH0298 = −3087.3 kJmol−1, S0298 = 348.5 Jmol−1 K−1, ΔfG0298 = −2632.3 kJmol−1 Starkeyite: ΔfH0298 = −2496.1 kJmol−1, S0298 = 259.9 Jmol−1 K−1, ΔfG0298 = −2153.8 kJmol−1 Kieserite: ΔfH0298 = −1611.5 kJmol−1, S0298 = 126.0 Jmol−1 K−1, ΔfG0298 = −1437.9 kJmol−1
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