The ΔG° for the following reaction is +70.9 kJ.?

Question

The ΔG° for the following reaction is +70.9 kJ.

SO3(g) → SO2(g) + 1/2ΔO2(g)
Given ΔG°f[ SO3(g)] = -371.0 kJ/mol, calculate ΔG°f [SO2(g)].

a.+441.9 kJ/mol
b.-300.1 kJ/mol
c.-5.23 kJ/mol
d.+300.1 kJ/mol
e.+5.23 kJ/mol

Answer 1

Since the free energy change for a reaction is equal to the free energies of formation of the of the products minus the free energy of formation of the reactants, and since you have all but one thing, it's an easy problem:

70.9 kJ = ΔG°f [SO2(g)] - ΔG°f[ SO3(g)]
70.9 = x - (-371.0)

Just solve for x.