For the reaction 3h2 (g) + n2 (g) 2nh3 (g), kc = 9.0 at 350°c. calculate g° at 350°c.

When ΔG° is the change in Gibbs free energy

So according to ΔG° formula:

ΔG° = - R*T * (㏑K)

here when K = [NH3]^2/[N2][H2]^3 = Kc

and Kc = 9

and when T is the temperature in Kelvin = 350 + 273 = 623 K

and R is the universal gas constant = 8.314 1/mol. K

So by substitution in ΔG° formula:

∴ ΔG° = - 8.314 1 / mol. K * 623 K * ㏑ (9)

= - 4536