Dinitrogen tetroxide and nitrogen dioxide form a temperature-dependent equilibrium described by the equation below.
N2O4(g)⇌2NO2(g)Kp=0.25 at 350K
A rigid 5.00 L cylinder at 350 K initially contains an equilibrium mixture with a total pressure of 3.00 atm.
(a) Derive expressions for the partial pressures of N2O4 and NO2 in terms of the equilibrium extent of dissociation x and the total pressure 3.00 atm. Then calculate the equilibrium partial pressures and the value of x.
(b) After equilibrium is established, an additional 0.500 atm of NO2 is injected rapidly into the cylinder, raising the total pressure to 3.50 atm. Determine the reaction quotient Qp immediately after the addition and predict the direction of the net reaction.
(c) Using an ICE analysis based on the new total pressure, calculate the final equilibrium partial pressures of N2O4 and NO2.
(d) Evaluate the change, if any, in the mole fraction of NO2 compared with its value in part (a), and explain how Le Châtelier’s principle accounts for the result despite the increased total pressure.