1. The problem statement, all variables and given/known data The thermal dissociation equilibrium of CaCO3 (s) is studied under different conditions. CaCO3 ⇔ CaO (s) + CO2 (g) For this equilibrium, the correct statement(s) is (are) (A) ΔH is dependent on T (B) Keq is independent of the initial amount of CaCO3 (C) Keq is dependent on the pressure of CO2 at a given T (D) ΔH is independent of the catalyst, if any Answers are (A), (B) and (D) 2. Relevant equations 3. The attempt at a solution I need someone to tell me if my justification for (A) is correct, and clear a doubt I have on (C). For (A), since this reaction is taken to be at equilibrium ΔG = 0. ΔG = ΔH - TΔS ⇒ ΔH = TΔS (at eq) Since ΔH ∝ T (A) is correct. I'm asking this because I think my reasoning might be wrong as I saw a justification involving Kirchhoff's law, http://chemwiki.ucdavis.edu/Core/Ph...namics/State_Functions/Enthalpy/Kirchhoff_Law For (C), I'm well aware that equilibrium constants are independent of concentrations of reactants and products, and they are a fixed value for a given reaction at a given temperature. However, I'm unable to reason why this is so. In this case Kp = (pco2)eq, i.e. partial pressure of CO2 at equilibrium. So isn't is directly dependent on the pressure of CO2, even though the pressure of CO2 at equilibrium is a fixed value at a given temperature and volume due to ideal gas law? Thank you!