question_answer 153)

  On the basis of Le Chatelier's principle explain how the temperature and pressure can be adjusted to increase the yield of ammonia in following reaction: \[{{N}_{2}}(g)+3{{H}_{2}}(g)\rightleftharpoons 2N{{H}_{3}}(g)\] \[\Delta H=-92.38kJ\,mo{{l}^{-1}}\] What will be the effect of addition of argon to the above reaction mixture at constant volume?

Answer:

  Effect of temperature: The reaction is exothermic, hence it will shift in forward direction by lowering the temperature. Thus, better yield of ammonia will be obtained at low but moderate temperature, otherwise reaction will become very slow. Effect of pressure:\[\Delta {{n}_{g}}=2-4=-2\]. Volume is decreasing in forward direction, hence it will shift in forward direction, on increasing the pressure. Effect of inert gas addition: At constant volume, there is no effect of addition of Argon.