Given the reaction: 2NaHCO3(s)Na2CO3(s)+CO2(g)+H2O(g) 1) Calculate Hrxn 2) Calculate Srxn 3) Calculate Grxn using: Grxn=HrxnTTSrxn 4) Calculate G rxn using: Gf values (This is exactly the same procedure as calculating Hrxn using Hf values) 5) Calculate T (the temperature where Grxn=0. It is where the reaction switches between being spontaneous and non-spontaneous and may also be referred to as Tcritical)