Final answer:
To find the standard free energy change (ΔG°rxn) for the given reaction, we subtract the sum of the standard free energies of formation of the reactants from the sum for the products. Plugging the given values into the relevant formula yields a ΔG°rxn of approximately -3297.7 kJ, which is closest to option A. -3.298 x 103 kJ.
Step-by-step explanation:
To calculate the standard free energy change (ΔG°rxn) for the reaction (4 HNO3(g) + 5 N2H4(l) → 7 N2(g) + 12 H2O(l)) we need to use the standard free energies of formation (ΔG°f) of the reactants and products. The formula for this is:
ΔG°rxn = Σ(ΔG°f products) - Σ(ΔG°f reactants)
Substituting known values, the equation becomes:
ΔG°rxn = [(7 mol N2 × 0kJ/mol) + (12 mol H2O(l) × -237.1kJ/mol)] - [(4 mol HNO3(g) × -73.5 kJ/mol) + (5 mol N2H4(l) × 149.3 kJ/mol)]
ΔG°rxn = [(0 kJ) + (-2845.2 kJ)] - [(-294 kJ) + (746.5 kJ)]
ΔG°rxn = -2845.2 kJ + 294 kJ - 746.5 kJ
ΔG°rxn = -3297.7 kJ
Therefore, the closest answer is A. -3.298 x 103 kJ.