Question

The reaction between nitrogen and hydrogen to give ammonia is an example of:
A.Decomposition reaction
B.Combination reaction
C.Synthesis reaction
D.Displacement reaction

Answer 1

Hint: 1 mole of ammonia reacts with 3 mole of hydrogen to give 2 mole of ammonia, such that breaking and formation of bonds combine to form a single product. Only one product is being formed.

Complete step by step answer:
The reaction between ammonia and hydrogen to give ammonia is known as Haber process. The Haber process is also known as the Haber-Bosch process. It is the process of fixing atmospheric nitrogen with hydrogen gas to give ammonia using a metal catalyst. Due to the strong triple bond present in nitrogen gas molecules, this process needs a catalyst that will accelerate the breaking of this triple bond. The major source of hydrogen is from natural gas like methane. This process is typically conducted at high temperature (400-500 degree Celsius) and high pressure (100 bar). This process is mainly used for industrial production of ammonia.
The balanced reaction of this process is $${\text{N}}_2\left(g\right)+3{\text{H}}_2\left(g\right)\to 2\text{N}{\text{H}}_3\left(g\right)$$ .
It is an exothermic and reversible reaction.
Decomposition reactions are those reactions in which one reactant breaks into two or more than two compounds. These reactions are just opposite to chemical synthesis. For example decomposition of calcium carbonate into calcium oxide and carbon dioxide.
Combination reactions are those reactions in which breaking and making of bonds between atoms occurs to produce new substances or when two or more compounds combine to form a single product. Such reactions are known as combination reactions. For example: formation of ammonia using nitrogen and hydrogen, formation of glucose using carbon dioxide and water.
Synthesis reactions are those reactions in which generally elements combine to form compounds. For example: synthesis of water using hydrogen and oxygen, synthesis of sulphur dioxide using sulphur and oxygen.
Displacement reactions are those reactions in which ions are exchanged between compounds. For example formation of iron sulphate using iron and copper sulphate solution, formation of lead chloride using lead and copper chloride solution.

Thus, the correct option is B.

Note:
The reaction in which formation of precipitation occurs is known as precipitation reaction. For example mixing of sodium sulphate and barium chloride forms precipitates of barium sulphate and sodium chloride. Ammonia is very pungent smelling gas. It is highly soluble in water.