Chemical Equilibrium Question

• LastRide7

  18 Jul 11, 23:18

  A pure sample of N2O4 (l) is introduced into an evacuated vessel. The vesse, of constant volume, is heated to a constant temperature such that the equilibrium below is established:
  
  2NO2 (g) <---> 2NO (g) + O2 (g)
  
  The value of the pressure p is then found to be 20% greater than if only NO2 (g) were present. Calculate the mole fraction, x, of oxygen in this equilibrium mixture.

• UltimaOnline

  19 Jul 11, 02:09

  2NO2 (g) <---> 2NO (g) + O2 (g)
  1 | 0 | 0
  -2x | +2x | +x
  1-2x | 2x | x
  
  Total pressure = 1+x
  
  Since (1+x)/(1) = 120/100, hence :
  1 + x = 1.2
  x = 0.2
  
  Therefore mole fraction of oxygen = (0.2)/(1.2) = 0.16666 = 0.167 (to 3 sf)