Consider the decomposition of a metal oxide to its elements, where M represents generic metal.
M2O (s) <> 2M (s) + 1/2 O2 (g)
Substance Delta G
M2O 6.30
M 0
O2  0
1) What is the standard change in Gibbs energy for the reaction, as written, in the forward direction?
2) What is the equilibrium constant of this reaction, as written, in the forward direction at 298K?
3) What is the equilibrium pressure of O2 over M (s) at 298k?
2 Answers

1) Delta G = 0  (6.3) = 6.3
2) delta G = RTln(K)
6.3 = R298ln(K)
ln(K) = 2.54*10^3
K = 1 (maybe delta G = 6.3 kJ)
3)
K = 1 = p^0.5
p = 1

K is 0.0786
p is 0.00619
but his way is correct