Question

How is ammonia collected?
(A)-Ammonia is less dense than air so it is collected by upward delivery
(B)- Ammonia is denser than air so it is collected by upward delivery
(C)- Ammonia is less dense than air so it is collected by downward delivery
(D)-None of the above

Answer 1

Hint: Upwards delivery method is used for gases which are soluble in water and has lighter density as compared to air for example chlorine. Downwards delivery is used for gases which are soluble in water and are heavier than air.

Complete solution step by step:
-industrially, Ammonia is produced by the Haber Bosch process. In this reaction molecular nitrogen reacts with molecular hydrogen in a gaseous phase.
-This reaction is a reversible reaction. So, Ammonia, molecular nitrogen and molecular hydrogen exist in an equilibrium.
-To increase the yield of ammonia, Le chatelier principle is applied which states, when any stress is applied on a system, the system will adjust itself in such a way that the effect of stress is reduced or nullified.
-As formation of ammonia is an exothermic reaction, by decreasing the temperature of reaction, yield of ammonia can be increased.
- \[{{N}_{2}}+3{{H}_{2}}\leftrightharpoons2N{{H}_{3}}\]
Number of moles of ammonia are 2, so to increase the yield, equilibrium should be shifted from left to right. So, by increasing pressure, no of moles increases, to reduce this change, reaction occurs in forward direction and yield of ammonia increases.

As Ammonia is less dense than air, it is collected by upward delivery, so option A is correct.

NOTE: In upward delivery method, the gas jar is connected to the flask. Gas less dense than air starts rising on top of the jar. Ammonia is soluble gas so the apparatus should be completely dry. Initially ammonia was mostly produced by dry distillation of animal waste products that were rich in nitrogen. Distillation of these waste products leads to reduction of nitrites and nitrous acids with hydrogen.