Question

At what temperature is the free energy change for the following reaction equal to zero? 2NO(g) + O2 (g) =2NO2(g)

Answer 1

ΔH^o_rxn = ΔH^o_products - ΔH^o_reactants

            = 2 ΔH^o_NO2 - (ΔH^o_O2 + 2 x ΔH^o_NO)

            = 2 x 33.18 - (0+ 2 x 90.25)

            = - 114.14 kJ/mol

ΔS^o_rxn = ΔS^o_products - ΔS^o_reactants

            = 2 ΔS^o_NO2 - (ΔS^o_O2 + 2 x ΔS^o_NO)

            = 2 x 240 - ( 205 + 2 x 210.6)

           = - 146.2 J/K

ΔG^o_rxn = ΔH^o_rxn - T x ΔS^o_rxn

0 = - 114.14 - T x (- 146.2 x 10^-3)

T = 780.7 K

temperature = 780.7 K