The acid dissociation constant for a weak acid HX at 25°C is 4.3 10^-⁸.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 -208.3 kJ/mol and 0,respectively.

Question

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The free energy change for the dissociation of HX can be calculated using the relation: ΔG° = -RT ln Ka where ΔG° is the standard free energy of formation for X^-(aq), R is the gas constant (8.314 J/mol K), T is the temperature in Kelvin (25°C = 298 K), and Ka is the acid dissociation constant for HX. Substituting the given values, we get: ΔG° = -8.314 J/mol K x 298 K x ln (4.3 11eaa8f0_66da_bd70_93a6_a9ce941267d5_TB6423_11 10^-⁸) / 1000 J/kJ ΔG° = -166 kJ/mol Therefore, the correct answer is D) -166 kJ/mol.

The Acid Dissociation Constant for a Weak Acid HX at 25°C