Heat of formation of calcium aluminate tricarbonate at 25 °C
- 1 September 1965
- journal article
- Published by National Institute of Standards and Technology (NIST) in Journal of Research of the National Bureau of Standards Section A: Physics and Chemistry
- Vol. 69 (5) , 407-416
- https://doi.org/10.6028/jres.069A.043
Abstract
The heat of formation at 25 °C, Δ H f ° = -16,228 kJ/mole, of calcium aluminate tricarbonate, 3CaO·Al2O3·3CaCO3·30H2O (c), was determined by the heat-of-solution method, with 2N HCl as the solvent, and 3CaO·A12O3· 6H2O (c) and CaCO3 (c) as the reactants. The heat of solution in 2N HCl is -501.0 kJ/mole, and the heat of the reaction 3CaO· A12O3. 6H2O (c) + 3CaCO3 (c) + 24H2O (1) →3CaO· A12O3· 3CaCO3·30H2O (c) is -186.6 kJ. The rate at which the heat of solution in 2N HCl changes with H2O content at the 30H2O level, dv(ΔH)/dn, is + 9.0 kJ/mole per mole H2O. Heats of solution were determined for samples in the range of 6 to 31H2O, but decomposition appears to occur on drying to H2O contents lower than 26H2O. The heats of stop wise reactions leading to the formation of calcium aluminate mono- and tricarbonate have also been calculated.Keywords
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