Cuestiones adicionales de equilibrio

1. PCl5(g) and Cl2(g) were placed in a sealed flask and allowed to reach equilibrium at 200 °C. The enthalpy change, ΔH, for the decomposition of PCl5(g) is positive.

a. Deduce the equilibrium constant expression, K , for the decomposition of PCl (g).

b. Deduce, giving a reason, the factor responsible for establishing the new equilibrium after 14 minutes.


2. The Contact process involves an exothermic reversible reaction:

2SO2(g) + O2(g) ⇌ 2SO3(g) Kc>>1 at 200 °C and 1 atm

a. Deduce the extent of the reaction at 200 °C and 1 atm.

b. The Contact process operates at a temperature of 450 °C and a pressure of 2 atm as optimum conditions for the production of SO3. Outline the reasons for choosing these conditions.

c. An engineer at a Contact process plant hypothesized that using pure oxygen, instead of air, would increase the profits. Comment on whether or not her hypothesis is valid, giving your reasons.


3. An equilibrium occurs between nitrogen dioxide, NO2, and dinitrogen tetroxide, N2O4.

2 NO2 = N2O4

a. Deduce the equilibrium constant expression, Kc, for this reaction.

b. Explain the effect on the position of the equilibrium and on the value of Kc when: i) pressure is decreased and temperature is kept constant; ii) temperature is increased and pressure is kept constant.