20. For the reaction at 800 K: N2(g) + 3F2(g)→2NF3(g), an equilibrium mixture contains the partial pressures of P(nitrogen) = 0.021 atm, P(fluorine) = 0.063 atm, and P(nitrogen trifluoride) = 0.48 atm. The △G° for the reaction at 527°C is thus _____kJ/mol.
(A) 17
(B)-50
(C) 50
(D)-17
(E)-71