Question

Manufacture of ammonia from the elements is represented by
\[{N_2}\, + \,3{H_2}\, \rightleftharpoons \,2N{H_3}\, + \,22.4kcal\]
The maximum yield of ammonia will be obtained when the process is made to take place:
A. At low pressure and high temperature
B. At low pressure and low temperature
C. At high pressure and high temperature
D. At high pressure and low temperature

Answer 1

Hint:Haber’s process is one the famous method to manufacture the ammonia from the elements. In this process the combination of nitrogen from the air with hydrogen from natural gas (i.e., methane) into ammonia. This process yields the maximum product at certain temperature and pressure. The production of ammonia is an exothermic process.


Complete step by step solution:
In Haber’s process, the combination of nitrogen from the air with hydrogen from natural gas (i.e., methane) forms into ammonia. This reaction is a reversible reaction. This process yields the maximum product at low temperature and high pressure. The production of ammonia is an exothermic process. In this reaction, the \[1\] mole nitrogen ( \[N\] ) and \[3\] moles of hydrogen (\[H\]) to form \[2\] moles of ammonia ( \[N{H_3}\]) .
To increase the yield, it follows Le Chatelier's principle.
\[{N_2}\, + \,3{H_2}\, \rightleftharpoons \,2N{H_3}\, + \,22.4kcal\]
In this reaction, only 15% of nitrogen and hydrogen is converted into ammonia. To increase the amount of ammonia the equilibrium is shifted towards the right.
To increase the amount of ammonia, the pressure is increased and the temperature is decreased by following Le Chartelier’s principle.
The high pressure is maintained due to the fewer moles of the product which are than the reactants.
\[\,\Delta {n_g} = \,2\, - (1 + 3)\, = \, - 2\]
\[\Delta {n_g} < \,0\]
The low temperature favours the exothermic reaction.
So, the answer for this is at high pressure and low temperature the maximum amount of yield is produced.

Therefore, the correct option is C. Formalin.


Note:If the pressure is increased in this reaction, the equilibrium shifts towards the product side since the product is having fewer moles than the reactant which means it leads to more product formation. Therefore, more ammonia formation takes place. According to Le Chatelier’s principle, if a system is disturbed at equilibrium the position of equilibrium will shift towards the direction so that the effect of change can be nullified.