Ammonia is manufactured in a sealed steel vessel at 450 °C by the reaction
N₂(g) + 3 H₂(g) ⇌ 2 NH₃(g) Kp=4.34×10−3 at 450 °C
A reactor of fixed volume 10.0 L initially contains the following partial pressures at 450 °C:
PN2=4.0atmPH2=9.0atmPNH3=0.80atm
The reactor is then rapidly expanded to a volume of 20.0 L while the temperature remains constant.
(a) Calculate the partial pressure of each species immediately after the expansion but before any shift in chemical equilibrium occurs.
(b) Using the pressures from part (a), determine the numerical value of the reaction quotient Qp and compare it to Kp to decide the direction in which the reaction will proceed to re-establish equilibrium.
(c) Construct a stoichiometric equilibrium table for the expanded system and solve for the new equilibrium partial pressure of each species.
(d) Compute the percentage change in the mole fraction of ammonia from just before the expansion to after the new equilibrium is established. Explain how the sign and magnitude of this percentage change are related to Le Châtelier’s principle.