You have a 100 mMoles of A in the 10 ml reaction mixture which contains buffer and enzyme. The reaction is allowed to reach equilibrium at 25 o C and you measure the concentration of B as 10 mM. What is the delta Go' for the reaction in KJ.

Wouldn't dGo be -RT*lnK

............A ==> B
I...........100...0
C...........-x....x
E..........100-x..10
Since x = 10, then 100-x = 90.
Solve for K, then substitute into the above equation to obtain dGo in J, convert kJ.