Heat of Formation of Calcium Aluminate Monocarbonate at 25 °C.

Abstract

The heat of formation of 3CaO·Al2O3·CaCO3·10.68H2O at 25 °C was determined by the heat-of-solution method, with 2N HCl as the solvent and 3CaO·Al2O3·6H2O and CaCO3 as the reactants. The heat of solution of CaCO3, to form dissolved CO2, was obtained by a new technique and a modified calculation which served to include the heat of vaporization of the gas escaping in the reaction and resulted in a higher value than those obtained by Wells and Tayıor and by Bäckström in determinations representing only partial solution of CO2. The results obtained were: kj/molekcal/mole3CaO·Al2O3·CaCO3·10.68H2O Heat of formation from elements, Δ H f ° -1956 from reactants and H2O-18.9 Heat of solution in 2N HCl-532.9-127.43CaO·Al2O3·6H2O Heat of solution in 2N HCl-576.6-137.8CaCO3 Heat of solution in 2N HCl-35.0-8.4.