Question

At 33K. N₂H₄ is fifty percent dissociated. Calculate the standard free energy change at this temperature and at one atmosphere.

Answer 1

T = 33K 

N₂O₄ ⇌ 2NO₂ 

Initial concentration 100% 

Concentration dissociated 50% 

Concentration remaining at equilibrium 50% – 100%

K_eq = 100/50 = 2 

∆G° = -2.303 RT log K_eq 

∆G° = -2.303 x 8.31 x 33 x log 2 

∆G° = -190.18 J mol^-1