Question

In the manufacture of ammonia by Haber’s process, the condition which would give maximum yield is: \[{N_2} + 3{H_2} \rightleftharpoons 2N{H_3} + Q\,kcal\]
A.High temperature, high pressure and high concentrations of the reactants
B.High temperature, low pressure and low concentrations of the reactants
C.Low temperature and high pressure
D.Low temperature, low pressure and low concentration of \[{H_2}\]

Answer 1

Hint: In this question, we have to first determine the type of changes that take place because of this reaction. These changes can be both physical and chemical in nature. Then the conditions that promote these changes must be incorporated to get the maximum yield in any given reaction.

Complete step by step answer:
The Haber process is used for producing ammonia. The reaction involved in this process can be given as follows: \[{N_2} + 3{H_2} \rightleftharpoons 2N{H_3} + Q\,kcal\].
Now for understanding the conditions that are the most favourable for this process, we need to understand the changes that are involved with this process.
The formation of ammonia using Haber’s Process involves the release of energy. This means that the formation of ammonia is an exothermic process.
In Haber’s Process, 4 moles of reactants form 2 moles of product. Hence the number of moles of the product formed is less than the number of reactants.
Now to favour the above-mentioned conditions, we need to provide the following conditions:
For an exothermic process to proceed at a faster pace, the surrounding temperature must be low. This is in accordance with the laws of thermodynamics.
In a reaction where the number of moles of the reactants is greater than the number of moles of product, the most favourable condition to complete the reaction is increasing the pressure of the entire setup.
Hence, in the manufacture of ammonia by Haber’s process, the condition which would give maximum yield is low temperature and high pressure

Hence, Option C is the correct option.

Note:
Another way to get the maximum yield is the introduction of a catalyst. In Haber’s Process, iron can be used as a catalyst. It helps to achieve an acceptable yield in an acceptable time.