Answer to Question #98791 in General Chemistry for Muhammad

Question

One of the steps in the production of nitric acid involves the reaction of ammonia and
oxygen to form nitrous oxide:
2NH3(g) + 2.5O2(g) --> 2NO(g) + 3H2O(g) + heat
Using Le Ch telier’s principle, describe and explain four ways in which an industrial
chemist could increase the yield of nitrous oxide. (4 marks)

Answer 1

Reaction:

2NH₃(g) + 2,5O₂(g) = 2NO(g) + 3H₂O(g) + heat (exothermic reaction)

Le Chateleier’s principle states: “When an equilibrium system is disturbed, it will adjust to diminish the change that has been made to it”.

There are 4 factors that can influence the equilibrium state: changes of pressure, temperature, concentration and addition of a catalyst.

1. The increasing of pressure causes the shift of equilibrium towards the reaction, where smaller volume of gases is formed. In our case, there are 4.5 moles of gas in the left part of the reaction, and 5 moles in the right part. So, if the pressure decreases, the equilibrium will shift towards the increasing of NO yield.

2. The increasing of temperature promotes the endothermic reaction. There is an exothermic reaction. Therefore, to increase the NO yield, the temperature must be decreased.

3. The increasing of concentration of the reagents leads to a shift in equilibrium toward their use. In our reaction, increasing the concentration of either NH₃ or O₂ will increase the NO yield. Also, the decreasing of products concentration leads to a shift in equilibrium the right.

4. Addition of a catalyst makes the reaction possible and towards the increasing of NO yield.