In the Haber process, ammonia is synthesized from nitrogen and hydrogen:

N₂(g) + 3H₂(g) → 2NH₃(g)

ΔG° at 298 K for this reaction is -33.3 kJ/mol. The value of ΔG at 298 K for a reaction mixture that consists of 1.0 atm N₂, 3.0 atm H₂, and 0.50 atm NH₃ is ________.