A calorimetric determination of the standard enthalpies of formation of huntite, CaMg3 (CO3)4 , and artinite, Mg2(OH)2 CO3 * 3H2O, and their standard Gibbs free energies of formation

Journal of Research of the U.S. Geological Survey
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Abstract

The enthalpies of formation, ΔH°f, of huntite, CaMg3(CO3)4 , and artinite, Mg2(OH)2CO3 * 3H2O, have been determined by HCl solution calorimetry using a constant-volume isoperibol reaction calorimeter. For the reaction CaO(c) + 3MgO(c) + 4CO2 (g) = CaMg3(CO3)4 (c), the enthalpy change at 298.15 K, ΔH°298 , is -123,203±145 cal mol-1. For the reaction 2MgO(c) + 4H2O(l) + CO2(g)=Mg2(OH)2CO3 * 3H2O(c), we obtained -45,132±100 cal mol-1. These results combined with the standard enthalpies of formation of CaO, MgO, H2O, and CO2 lead to ΔH°298 (huntite) = -1,082,600±375 cal mol-1 and ΔH°298  (artinite) = -698,043±170 cal mol-1. Using recently determined values for the standard entropies of huntite, CaMg3(CO3)4, and artinite, Mg2(OH)2CO3 * 3H2O, and of Mg, Ca, C, O2 , and H2 , we calculate ΔG°f,298 (huntite) = -1,004,707±390 cal mol-1 and ΔG°f,298 (artinite) = -613,924±180 cal mol-1.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title A calorimetric determination of the standard enthalpies of formation of huntite, CaMg3 (CO3)4 , and artinite, Mg2(OH)2 CO3 * 3H2O, and their standard Gibbs free energies of formation
Series title Journal of Research of the U.S. Geological Survey
Volume 1
Issue 5
Year Published 1973
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Description 7 p.
First page 535
Last page 541
Online Only (Y/N) N
Additional Online Files (Y/N) N
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