Enthalpies of formation of chromium carbides

Abstract

Adiabatic oxygen combustion calorimetry has been used to determine the enthalpies of combustion of the chromium carbides Cr₂₃C₆, Cr₇C₃ and Cr₃C₂ to be—15,057.6±12.4 kJ ·mole⁻¹,—4985.3±3.8 kJ ·mole⁻¹ and—2400.5±0.9 kJ ·mole⁻¹ respectively. The products of combustion in all cases were Cr₂O₃ and CO₂. Using standard data for Cr₂O₃ and CO₂, the enthalpies of formation of the carbides have been calculated to be:fΔH ^o₂₉₈ Cr₂₃C₆=−290.0±27.6 kJ·mole⁻¹ fΔH ^o₂₉₈ Cr₇C₃=−149.2±8.5 kJ·mole⁻¹ fΔH ^o₂₉₈ Cr₃C₂=−81.1±2.9 kJ·mole⁻¹