Low-temperature heat capacity and entropy of chalcopyrite (CuFeS 2): estimates of the standard molar enthalpy and Gibbs free energy of formation of chalcopyrite and bornite (Cu 5FeS 4)

Abstract

The heat capacity of CuFeS 2 (chalcopyrite) was measured between 6.3 and 303.5 K. At 298.15 K, C p,m o and S m o( T) are (95.67±0.14) J·K −1·mol −1 and (124.9±0.2) J·K −1·mol −1, respectively. From a consideration of the results of two sets of equilibrium measurements we conclude that Δ f H m o(CuFeS 2, cr, 298.15 K) = −(193.6±1.6) kJ·mol −1 and that the recent bomb-calorimetric determination by Johnson and Steele ( J. Chem. Thermodynamics 1981, 13, 991) is in error. The standard molar Gibbs free energy of formation of bornite (Cu 5FeS 4) is −(444.9±2.1) kJ·mol −1 at 748 K.