Peculiarities of CaCO3, SrCO3 and BaCO3 decomposition in CO2 as a proof of their primary dissociative evaporation

The results of thermogravimetric experiments on the decompositions of CaCO₃, SrCO₃ and BaCO₃ in the presence of CO₂ and some data reported in the literature were used for the determination of the E parameter of the Arrhenius equation by the third-law method. The values obtained (495, 569 and 605 kJ mol⁻¹) are twice as much compared with the values of the E parameter obtained for these carbonates earlier in the absence of CO₂. This fact together with the invariance of the E parameter with partial pressure of CO₂ (P_CO2) and a hyperbolic dependence of the rate of decomposition on P_CO2 is in excellent agreement with the theoretical predictions deduced from the mechanism of decomposition that includes the primary stage of dissociative evaporation of reactant.