For a gaseous reaction standard conditions are 298K and part

For a gaseous reaction, standard conditions are 298K and partial pressure of 1atm for all species.
For the reaction:
2NO(g) + O2(g) <--> 2NO2(g)

the standard change in Gibbs free energy is DeltaG= -32.8kJ/mol. What is deltaG for this reaction at 298K when the partial pressures are:
PNO= .200atm, P02=.100atm, PNO2= .850atm

Solution

Kp for reaction = p^2No2/p^2No x pO2 = (0.85)^2/(0.2)^2(0.1) = 180.625,

delta n for reaction = 2-1-2 = -1,

Kp = Kc(RT)^delta n , Kp = Kc(RT)^-1,

Kc = Kp(RT) = 180.625 x0.0821x298 = 4419.135,

dG = dGo + RT ln Kc

dG = -32.8 + [(8.314x298)/1000] ln(4419.135)

dG = -12 KJ/mol