Question

Determine ∆G° for 2 NO₂(g) → N₂O₄(g) at 25°C.

NO2 = 51.3
N2O4 = 97.8

Answer 1

Are those values \(∆G_f°\) values?

Answer 2

Yes they are.

Answer 3

Use the formula \[∆G°=\sum ∆G_f° _\text{products}- \sum ∆G_f°_\text{reactants}\]
Don't forget to consider stoichiometry. For NO2, you have to consider the '2' in the reactants (i.e., multiply the free energy of formation by 2, because it's 51.3 kJ/mol of reactant or product, and here you have 2 mols). Units are in \(kJ/mol_{rxn}\)