20. The acid dissociation constant for a weak acid HX at 25°C is 3.0 × 10⁻⁹. Calculate the free energy of formation for X⁻(aq) at 25°C. The standard free energies of HX(aq) and H⁺(aq) at 25°C are -203.4 kJ/mol and 0, respectively. (A) -199 kJ/mol (B) 252 kJ/mol (C) 0 (D) -155 kJ/mol (E) -252 kJ/mol