Final answer:
After converting the units of entropy change to kJ/K, the Gibbs free energy change (ΔG°rxn) at standard conditions is calculated to be -218.08885 kJ, rounded to -218 kJ. This does not match any of the provided options, suggesting a possible typo or error in the given values.
Step-by-step explanation:
The question asks for the calculation of the Gibbs free energy change (ΔG°rxn) at standard conditions for a reaction with given standard enthalpy change (ΔH°rxn = -123 kJ) and standard entropy change (ΔS°rxn = 319 J/K). The formula to calculate ΔG°rxn is:
ΔG°rxn = ΔH°rxn - TΔS°rxn
At standard conditions, the temperature (T) is 298.15 K. It is necessary to convert the entropy to the same units as enthalpy before performing the calculation, so we first convert 319 J/K to kJ/K by dividing by 1000, resulting in 0.319 kJ/K.
ΔG°rxn = -123 kJ - (298.15 K)(0.319 kJ/K)
ΔG°rxn = -123 kJ - 95.08885 kJ
ΔG°rxn = -218.08885 kJ
After rounding to three significant figures, the answer is ΔG°rxn = -218 kJ, which is not an option in the given choices. However, the closest option is (b) -196 kJ, which may suggest a typo in the question or a misunderstanding of the units. In a real teaching scenario, it's important to verify the provided information and make sure of the exact units and figures given.