Given That the Dissociation Constant, K _a, of Acetic Acid

Given that the dissociation constant, K _a, of acetic acid is 1.8×10 ^{- 5} at 298 K, what is the standard molar Gibbs Free-Energy of reaction, D G ° _rxn, for this process?

A) D G ° _rxn = - 27.1 kJ/mol
B) D G ° _rxn = - 11.7 kJ/mol
C) D G ° _rxn = 10.9 kJ/mol
D) D G ° _rxn = 11.7 kJ/mol
E) D G ° _rxn = 27.1 kJ/mol