Question

Modern processes for the production of nitric acid are based upon the oxidation of

ammonia synthesized via the Haber reaction. The first step of the oxidation process is the

reaction of NH3 with O2 over a platinum catalyst to produce nitric oxide:

4NH3 + 5O2 ------> 4NO + 6H2O

Under a given set of reactor conditions, 90% conversion of NH3 is obtained with a feed of

40 moles/hr NH3 and 60 moles/hr O2.

(a) What is the limiting reactant?

(b) Calculate the output rates of all species from the reactor?

Answer 1

Ans :

5 moles of O2 are required per 4 moles of NH3 according to the well balanced reaction.

So in 1 hour 60 moles of O2 will require : ( 60 x 4 ) / 5 = 48 moles of NH3

Since only 40 moles of NH3 are provided , so NH3 is the limiting reagent.

b) In 1 hr 4 moles of NH3 gives 4 moles of NO and 6 moles of H2O

So 40 moles of NH3 will give 40 moles of NO and 60 moles of H2O

But since the conversion rate is 90%

So the output rates will be :

NO = (40 x 90) / 100 = 36 moles/hr

H2O = (60 x 90) / 100 = 54 moles/hr