At 60°c,one mole of dinitrogen tetroxide is fifty percent dissociatedN2O4⇌2NO2. the standard free energy change at this temperature and at 1atm.(log 1.33 = 0.1239)

N2O4(g)⇌2NO2(g)       1mol          2mol    1-x               2x where x=50%=0.5 XN2O4=0.51.5 =13 ;    XNO2=11.5=23 PN2O4 =13×1 atm. ;   PNO2=23×1 atm. Equilibrium constant , KP= PNO22PN2O4=23×2313=1.33 atm∆Go=-2.303RTlogKP           =-2.303(8.314)333(0.1239)            =-790 J mol-1