Question

Calculate the standard enthalpy change (ΔH°) and standard entropy change (ΔS°) for the decomposition reaction of calcium carbonate (CaCO3) at 298 K:CaCO3(s) → CaO(s) + CO2(g)

Answer 1

To calculate the standard enthalpy change  H  and standard entropy change  S  for the decomposition reaction of calcium carbonate  CaCO3  at 298 K, we need to use the standard enthalpies of formation  Hf  and standard molar entropies  S  of the substances involved in the reaction.The standard enthalpies of formation  Hf  for the substances are as follows:CaCO3 s : -1206.9 kJ/molCaO s : -635.1 kJ/molCO2 g : -393.5 kJ/molThe standard molar entropies  S  for the substances are as follows:CaCO3 s : 92.9 J/molKCaO s : 39.8 J/molKCO2 g : 213.8 J/molKNow, we can calculate the standard enthalpy change  H  for the reaction using the following equation:H =  [Hf products ] -  [Hf reactants ]H = [ -635.1 kJ/mol  +  -393.5 kJ/mol ] - [ -1206.9 kJ/mol ]H =  -1028.6 kJ/mol  -  -1206.9 kJ/mol H = 178.3 kJ/molNext, we can calculate the standard entropy change  S  for the reaction using the following equation:S =  [S products ] -  [S reactants ]S = [ 39.8 J/molK  +  213.8 J/molK ] - [ 92.9 J/molK ]S =  253.6 J/molK  -  92.9 J/molK S = 160.7 J/molKSo, the standard enthalpy change  H  for the decomposition reaction of calcium carbonate  CaCO3  at 298 K is 178.3 kJ/mol, and the standard entropy change  S  is 160.7 J/molK.