Thermochemistry of double carbonates in the K{sub 2}CO{sub 3}-CaCO{sub 3} system
- Princeton Univ., NJ (United States)
- Umea Univ. (Sweden); and others
Enthalpies of formation, {Delta}H{sub f}, of the double carbonates K{sub 2}Ca(CO{sub 3}){sub 3} (with two polymorphs, buetschliite and fairchildite) and K,Ca,(CO,), from the components K{sub 2}CO{sub 3} and CaCO{sub 3} were determined at 298 K by drop solution calorimetry in molten 2PbO{circ}B{sub 2}O{sub 3} at 974 K. The enthalpies of formation were -38.7 {+-} 3.2 kJ/mol for buetschliite, -5.1 - 3.3 U/mol for fairchildite and -7.2 {+-} 5.8 kJ/mol for K{sub 2}Ca{sub 2}(CO{sub 3}){sub 3}. The entropy changes for the formation, {Delta}S{sub f}, were also evaluated for the double carbonates. Assuming {Delta}S{sub f} (buetschliite) = 0, because of its ordered structure, the entropy of formation of fairchildite is 40.9 {+-} 5.1 J/mol{circ}K and of K{sub 2}Ca{sub 2}(CO{sub 3}){sub 3} is 39.4 - 7.3 J/mol{circ}K. 12 refs., 4 tabs.
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FG02-85ER13437
- OSTI ID:
- 543159
- Journal Information:
- American Mineralogist, Journal Name: American Mineralogist Journal Issue: 5-6 Vol. 82; ISSN AMMIAY; ISSN 0003-004X
- Country of Publication:
- United States
- Language:
- English
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