Standard Free Energy Change?

Calculate the standard free energy change at 25°C for the reaction 2NO(g) + O2(g) ===%26gt; 2NO2(g).





Species ______ DHf° (kJ/mol) _____ S° (J/K·mol)


NO(g) _________ 90.25 ___________ 210.8


O2(g) __________0.00 ____________ 205.1


NO2(g) ________33.18 ____________ 240.1





a. -4.69 kJ


b. -70.46 kJ


c. -157.82 kJ


d. -532.57 kJ

Standard Free Energy Change?
2NO(g) + O2(g) -----%26gt; 2NO2(g)


delta H = (2×33.18) - (2×90.25 + 1×0.00) = 66.36-180.50 = -114.14 kJ/mol


delta S = (2×240.1) - (2×210.8 + 1×205.1) = 480.2 - 421.6 - 205.1 = -146.5 J/K/mol


delta G = delta H - T×delta S = -114.14 - (298)(-0.1465) = -114.14 + 43.66 = -70.48 kJ/mol