HOW DID THE HABER-BOSCH PROCESS CHANGE THE WORLD?

Nitrogen

Nitrates are molecules of oxygen and nitrogen, which are abundant in the earth’s atmosphere. 

On every square metre of the earth’s surface, it contains eight metric tonnes of nitrogen. 

Nitrogen bond

The majority of the nitrogen in the air is N2. A triple bond is created when two nitrogen atoms unite to share three pairs of electrons, making the molecule practically unbreakable. 

At 946 kJ/mol, a relatively high amount of energy is needed to break the nitrogen triple bond. This makes molecular nitrogen nearly inert. 

Breaking of Nitrogen bonds

Atomic nitrogen can create ionic nitrides like ammonia (NH3), ammonium (NH4+), or nitrates (NO3–) when nitrogen bonds break. 

Paints require certain kinds of nitrogen, also known as reactive nitrogen, in order to synthesize proteins, amino acids, and enzymes. 

What is the nitrogen cycle? 

It is a biogeochemical process which transforms nitrogen into a variety of forms and allow nitrogen to go from the atmosphere to the soil to living things and back again. 

It involves several processes such as nitrogen fixation, nitrification, denitrification, etc.

Nitrogen fixation

Lightning

Lightning destroys the N2 triple bond. The nitrogen in the air then combines with oxygen to generate nitrogen oxides such as NO and NO2. 

Additionally, they can react with water vapor to produce HNO3 and HNO2, the nitric and nitrous acids, respectively. 

Rainfall fertilizes meadows, woodlands, and farmlands with reactive nitrogen-rich HNO3 and HNO2. About 10 kg of nitrogen are added to the soil annually per acre via this pathway.

Bacterial action

Atmospheric nitrogen is fixed by bacteria, which have a symbiotic relationship with certain plant species.

Legumes like peas, clover and peanuts have nodules on their roots which attract bacteria that convert atmospheric nitrogen into ammonia or ammonium, which can then be used to power the plant.

This process known as biological nitrogen fixation turns organic nitrogen gas into inorganic nitrogen compounds like ammonia and ammonium.

Some Examples are:

Azotobacter bacteria can generate reactive nitrogen. 

Microorganisms like Rhizobia have developed symbiotic relationships with legume plants such as clover, peas, beans, alfalfa, acacia, etc. to provide reactive nitrogen in exchange for nutrition. 

Azolla, which is a species of aquatic fern, forms a symbiotic association with the cyanobacterium Anabaena azollae. It can then absorb and convert nitrogen from the air into reactive nitrogen.

Nitrification

It is a process in which specialised bacteria and archaea transform ammonia into nitrite (NO2), which is subsequently transferred to a completely different group of prokaryotes that further oxidize the nitrite into nitrate (NO3-).

For example, terrestrial plants can absorb ammonium and nitrate by their root hairs. This is the process of how nitrogen is produced as a nutrient in soil and aquatic and marine ecosystems.

Ammonification

In this process, the nitrogen-rich nitrate is converted into ammonium, which can be picked back up by plants and used again.

Denitrification

The process of converting available nitrogen into atmospheric nitrogen is called denitrification. 

Certain anaerobic bacteria which don't require oxygen convert nitrate to nitrogen gas, which goes up into the atmosphere and along with the nitrogen cycle begins yet again.

PRACTICE QUESTION

Q.Consider the following statements about the Haber-Bosch process:

1. It is a method of directly synthesizing ammonia from hydrogen and nitrogen.

2. The process directly combines nitrogen from the air with hydrogen under low pressures.

3. The process made the manufacture of ammonia economically feasible. 

Which of the above  statements are correct? 

A. 1 and 3 only

B. 2 and 3 only

C. 1, 2 and 3 only

D. None

Answer: A

Explanation:

Statement 1 is correct: 

The Haber-Bosch process is a method of directly synthesising ammonia from hydrogen and nitrogen.

It was developed by the German physical chemist Fritz Haber. 

The method was made into a large-scale process by using a catalyst and high-pressure methods by Carl Bosch.

Statement 2 is incorrect: 

The process directly combines nitrogen from the air with hydrogen under extremely high pressures and moderately high temperatures. 

A catalyst which is made mostly from iron enables the reaction to be carried out at a lower temperature than practicable.

The lower the temperature and the higher the pressure used, the greater the proportion of ammonia yielded in the mixture. 

For commercial production, the reaction is carried out at pressures ranging from 200 to 400 atmospheres and at temperatures ranging from 750° to 1200° F.

Statement 3 is correct: 

Haber-Bosch was the first industrial chemical process to use high pressure for a chemical reaction. 

The process made the manufacture of ammonia economically feasible.