Nitrogen: Preparation, Properties, Uses & Nitrogen Cycle

Nitrogen has the atomic number 7 and the symbol N. It is a nonmetal and the lightest member of Group 15 of the periodic table, often known as pnictogens. It is a common element across the universe, with the Milky Way and Solar System having the sixth-highest total abundance. At typical temperatures and pressures, two atoms of the element combine to form N₂, a colourless and odourless diatomic gas. N₂ is the most common uncombined element in the atmosphere, accounting for 78 percent of the total. Nitrogen is found in all animals, in amino acids (and hence proteins), nucleic acids (DNA and RNA), and the energy transfer molecule adenosine triphosphate.

Nitrogen

Key Terms: Nitrogen, Nitrogen Cycle, Nitrogen Gas, Industrial Applications, Liquid Nitrogen

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Preparation of Nitrogen Gas

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Aqueous ammonium chloride and sodium nitrite solutions are heated to produce N2 

NH₄Cl (aq)+NaNO₂(aq) → NaCl(aq)+2H₂O (l)+N₂(g)

This reaction also produces a small amount of nitric oxide and nitric acid. By passing the gas into an aqueous sulphuric acid solution having potassium dichromate, the N₂ produced is purified.

(i) Thermal Decomposition of Ammonium Dichromate 

When red ammonium dichromate crystals are heated, a strong reaction occurs, accompanied by light flashes and nitrogen evolution.

(NH₄)2Cr₂O₇ → N₂+4H₂O+Cr₂O₃

(ii) By Oxidation of Ammonia 

Nitrogen is produced when ammonia is oxidised by the red hot copper oxide or chlorine.

2NH₃+3CuO  \(\to\)N₂+3H₂O+3Cu

8NH₃+3Cl_2 \(\to\)N₂+6NH₄Cl

(iii) By Sodium Azide Thermal Decomposition 

By heating sodium or barium azide, very pure nitrogen can be obtained. 

2NaN₃\(\to\)2Na+3N₂

Ba(N₃)₂\(\to\)Ba+3N₂

Nitrogen gas is produced industrially through fractional distillation of liquid air or mechanically utilising gaseous air (pressurised reverse osmosis membrane or pressure swing adsorption). Nitrogen gas generators that use membranes or pressure swing adsorption (PSA) are often less expensive and energy-intensive than bulk nitrogen delivery. 

Commercial nitrogen is frequently produced as a byproduct of air-processing for industrial oxygen concentration in steelmaking and other applications. It's known as OFN when it's delivered compressed in cylinders (oxygen-free nitrogen). Commercial-grade nitrogen currently includes no more than 20 parts per million of oxygen, and specially purified grades with no more than 2 parts per million of oxygen and 10 parts per million of argon are also available.

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Properties of Nitrogen Gas

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Physical and chemical properties of nitrogen are as follows.

Physical Properties

• Nitrogen is an odourless, tasteless, and colourless gas. 
• Nitrogen is non-poisonous, yet animals perish from a lack of oxygen in a nitrogen-rich environment. 
• Nitrogen has a very low water solubility (23.2 cm³ per litre of water at and pressure) 
• 63.2K and 77.2K are the melting and boiling points, respectively.

Chemical Properties

• At typical temperatures, N2 is practically non-reactive. It doesn't burn and doesn't allow combustions to take place. Because of the molecule's exceptional stability, N₂ is chemically inert at typical temperatures. 
• In a N₂ molecule, a triple bond connects the two nitrogen atoms. The bond enthalpy (the amount of heat energy needed to break a chemical bond) of the triple bond is extremely high. N₂ is almost unreactive with most chemicals because of its extremely high bond dissociation enthalpy. 
• At high temperatures, however, it forms nitrides, which are ionic and covalent compounds made up of some metals and non-metals. Below are a few of the most important N₂ chemical reactions.

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Uses of Nitrogen Gas

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• N₂ is mostly used in the production of ammonia. It is also used to make things like calcium cyanide, nitric acid, and other vital chemicals. 
• Nitrogen is utilised to create an inert environment in a variety of metallurgical processes. 
• Liquid nitrogen is a refrigerant that is used to preserve biological items and to freeze food. Cryosurgery makes use of it as well. 
• Nitrogen is employed as a reactive chemical's inert diluent.

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Nitrogen Cycle

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A cycle is a set of events or processes that occur on a regular basis. Nitrogen travels from the soil to plants, animals, and then back to the soil in the nitrogen cycle. It can be utilised again by another plant after it returns to the soil from a decaying plant. 

Nitrogen Cycle

There are five steps to the nitrogen cycle. 

• Fixing of nitrogen 
• Nitrification 
• Denitrification 
• Assimilation of nitrates 
• Ammonification. 

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Industrial Applications

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In the industrial sector, nitrogen is mostly used to make ammonia, which is used in explosives, fertilisers, and other products. However, nitrogen has a variety of other applications in many industries. Nitrogen is used in a variety of applications, including medications and food packaging. The following are examples of nitrogen's applications in several industries:

Food Packaging

Nitrogen is utilised in many food manufacturing processes to maintain food or beverage quality. Manufacturers are increasingly using compressed nitrogen to substitute oxygen when packaging perishable food items. Foods including vegetables, fruit, meats, and snacks can stay longer in the lack of oxygen. Furthermore, nitrogen protects food from spoilage during transportation.

Tires for Automobiles 

Car tyres pumped with nitrogen perform far better than compressed air tyres. Nitrogen in your automobile tyres might enhance your vehicle's fuel economy. Nitrogen, unlike compressed air, has a hard time escaping from the tire's cavity, ensuring that the pressure inside the tyre remains constant for a long time. The car's engine runs more smoothly when the pressure is optimal.

Blanketing with chemicals 

To remove oxygen from the manufacturing process, several firms utilise nitrogen in extremely explosive chemical facilities. It is commonly employed in dangerous environments such as factories, manufacturing facilities, and chemical plants to prevent explosions and fires. One can avoid explosions in their production facilities by lowering the oxygen level. 

Electronics 

Nitrogen is used to permanently join two components of an electronic gadget during assembly. Soldering is another name for this procedure. Nitrogen is employed in this technique to reduce the surface tension and facilitate a better break away from the electric bond. Nitrogen also helps to keep computers cool by keeping them from overheating.

Laboratory 

Researchers and scientists in laboratories require a specialised environment in which to conduct tests and obtain correct results. Nitrogen is utilised to regulate oxygen levels, temperature, and humidity in this way. As a result, the gas aids in preserving the ideal environment for sensitive processes and testing involving heavy machinery. Aside from that, several types of lab equipment necessitate nitrogen purging. 

Laser Cutting

Because nitrogen may be used for purging, it has become a necessary component for the steel industry as a whole. The nitrogen gas is often used to sweep away molten residue and assist in the production of a corrosion-resistant stainless or aluminized steel product.

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Things to Remember

• Nitrogen is found in all animals, particularly in amino acids (and hence proteins), nucleic acids (DNA and RNA), and the energy transfer molecule adenosine triphosphate.
• Nitrogen gas is produced industrially through fractional distillation of liquid air or mechanically utilising gaseous air (pressurised reverse osmosis membrane or pressure swing adsorption). 
• Commercial-grade nitrogen currently includes no more than 20 parts per million of oxygen, and specially purified grades with no more than 2 parts per million of oxygen and 10 parts per million of argon are also available.
• Nitrogen is utilised in many food manufacturing processes to maintain food or beverage quality. 
• Nitrogen is used in a variety of applications, including medications and food packaging.