A rigid tank contains an equal-molar mixture of N₂ and H₂. At the temperature of the vessel ammonia is formed by the reaction:

1/2 N₂ + 3/2 H₂ ---> NH₃

All components behave as ideal gases at the temperature and pressure of the system. The initial pressure before any reaction occurs is 760 mm Hg.

a) Calculate the moles of N₂ and the moles of H₂ consumed when the pressure has fallen to 550 mm Hg if the temperature has not changed.

b) What is the extent of the reaction?