Find delta G reaction

Question

ATP (aq) + H2O --> ADP (aq) + HPO4 2- (aq)

delta G^o rxn = -30.5 kj/mol at 37 C with pH of 7.0. Find delta G rxn in which [ATP] = 5.0 mM, [ADP] = 0.70 mM and [HPO4 2-] = 5.0 mM

Answer 1

We can use the expression ∆G = ∆Gº + RT ln Q

First we will determine Q:

Q = [ADP][HPO₄^2-] / [ATP]

Q = (0.70 mM)(5.0 mM) / 5.0 mM) = 0.7

∆G = -30.5 kJ/mol + (8.314 J/K-mol x 310K) ln 0.7

∆G = -30.5 kJ/mol + (0.008314 kJ/Kmol x 310K) ln 0.7

∆G = -31.4 kJ/mol