Thermodynamics

 

 66) T = 298 K          R = 8.314 J/mol•K

       (a) NaHCO3(s) NaOH(s) + CO2(g)

 

             Keq = PCO2

             Keq = e-ΔG°/RT

 

             ΔG°rxn = ΣΔGf°(products) - ΣΔGf°(reactants)

             ΔG°rxn = [ΔGf°(NaOH(s)) + ΔGf°(CO2(g))] - [ΔGf°(NaHCO3(s))]

             ΔG°rxn = [1 mol NaOH(s) x -379.5 kJ/1 mol NaOH(s) + 1 mol CO2(g) x -394.4 kJ/1 mol CO2(g)] - [1 mol NaHCO3(s) x -851.8 kJ/1 mol NaHCO3(s)]

             ΔG°rxn = 77.9 kJ

 

             -ΔG°/RT = -(77.9 kJ x 103 J/kJ)/(8.314 J/mol•K x 298 K) = -31.4 kJ

             Keq = e-ΔG°/RT = e-31.4 = 2 x 10-14

 

 

       (b) 2HBr(g) + Cl2(g) 2HCl(g) + Br2(g)

 

            Keq = PCO2

             Keq = e-ΔG°/RT

 

             ΔG°rxn = ΣΔGf°(products) - ΣΔGf°(reactants)

             ΔG°rxn = [2ΔGf°(HCl(g)) + ΔGf°(Br2(g))] - [2ΔGf°(HBr(g)) + ΔGf°(Cl2(g))]

             ΔG°rxn = [2 mol HCl(g) x -95.27 kJ/1 mol HCl(g) + 1 mol Br2(g) x 3.14 kJ/1 mol Br2(g)] - [2 mol HBr(g) x -53.22 kJ/1 mol HBr(g) + 0]

             ΔG°rxn = -80.96 kJ

 

             -ΔG°/RT = -(-80.96 kJ x 103 J/kJ)/(8.314 J/mol•K x 298 K) = 32.7 kJ

             Keq = e-ΔG°/RT = e32.7 = 2 x 1014

 

 

       (c) 2SO2(g) + O2(g) 2SO3(g)

 

            Keq = PCO2

             Keq = e-ΔG°/RT

 

             ΔG°rxn = ΣΔGf°(products) - ΣΔGf°(reactants)

             ΔG°rxn = [2ΔGf°(SO3(g))] - [2ΔGf°(SO2(g)) + ΔGf°(O2(g))]

             ΔG°rxn = [2 mol SO3(g) x -370.4 kJ/1 mol SO3(g)] - [2 mol SO2(g) x -300.4 kJ/1 mol SO2(g) + 0]

             ΔG°rxn = -140.0 kJ

 

             -ΔG°/RT = -(-140.0 kJ x 103 J/kJ)/(8.314 J/mol•K x 298 K) = 56.5 kJ

             Keq = e-ΔG°/RT = e56.5 = 3 x 1024