[Chemistry Class Notes] on Preparation, Properties and Uses of Nitrogen Pdf for Exam

Nitrogen was discovered in 1772 by Daniel Rutherford, a Scottish scientist. Lavoisier established its elemental nature and named it azote. The present name nitrogen is derived from nitre which is a well known nitrogenous compound. Nitrogen is the first element of group 15 of the periodic table and has electronic configuration 1s22s22p3. The molecular form of nitrogen is referred to as N2. The method of preparation of nitrogen and N2 (Dinitrogen) is the same. They have the same physical and chemical properties as well as uses. Nitrogen is an essential constituent of all vegetable and animal proteins which are vital for life processes. 

Laboratory Method of Preparation of Dinitrogen (N2)

In the laboratory, N2 is prepared by heating an aqueous solution of ammonium chloride and sodium nitrite.

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

Small amounts of nitric oxide and nitric acid are also formed in this reaction. The N2 thus obtained is purified by passing the evolved gas through an aqueous sulphuric acid solution containing potassium dichromate.

Other Methods of Preparation of N2

By Thermal Decomposition of Ammonium Dichromate 

When red crystals of ammonium dichromate are heated, a violent reaction takes place which is accompanied by flashes of light and evolution of nitrogen.

(NH4)2Cr2O7 →  N2+4H2O+Cr2O3

By Oxidation of Ammonia

When ammonia is oxidized by a red hot copper oxide or by chlorine, nitrogen is obtained.

2NH3+3CuO → N2+3H2O+3Cu

8NH3+3Cl2 → N2+6NH4Cl

By Thermal Decomposition of Sodium Azide

Very pure nitrogen can be obtained by heating sodium or barium azide.

2NaN3 → 2Na+3N2

Ba(N3)2 → Ba+3N2

Manufacturing of N2

Commercially, N2 is prepared by the fractional distillation of liquid air. 

Properties of Dinitrogen (N2)

Physical Properties of Dinitrogen (N2)

• It is a colorless, odorless, and tasteless gas.

• It is non-poisonous but animals die in an atmosphere of nitrogen for want of oxygen.

• It has very low solubility in water (23.2 cm3 per litre of water at and pressure)

• Its melting and boiling points are 63.2K and 77.2K respectively.

Chemical Properties of Dinitrogen (N2)

• N2 is almost non-reactive at ordinary temperatures. It neither burns nor supports combustion. The chemical inertness of N2 at ordinary temperatures is due to the high stability of the molecule.

• In a molecule of N2, the two nitrogen atoms are linked together by a triple bond. The triple bond has a very high bond enthalpy(amount of heat energy required to break a chemical bond) . Due to very high bond dissociation enthalpy, N2 is almost unreactive towards most of the reagents. 

• However, at high temperatures, it combines with some metals and non-metals to form ionic and covalent compounds called nitrides. Some important chemical reactions of N2 are given below.

Combination with Electropositive Metals

N2 combines with some highly electropositive metals at high temperatures forming their nitrides. Lithium nitride forms slowly at ordinary temperatures but rapidly at higher temperatures. Magnesium and aluminum continue burning in an atmosphere of nitrogen forming their nitrides. Calcium, strontium, and barium react with N2 when they are red hot.

6Li+N2→ 2Li3N2

3Mg+N2→ Mg3N2

2Al+N2 →  2AlN

3Ca+N2→  Ca3N2

Combination with O2

N2 combines with O2 in the presence of an electric arc (above 3273K) to form nitric oxide.

N2+O2→ 2NO

Equations

1. What happens when N2 combines with H2?

N2 reacts with H2 at 725K under a pressure of 200 atmospheres in presence of a catalyst (finely divided iron and molybdenum).

N2+3H2→ 2NH3

2. Write chemical equations for the reaction of N2 with Alumina and Calcium Carbide.

Al2O3+N2+3C → 2AlN+3CO

CaC2+N2→ CaCN2+C

CaCN2 or Calcium cyanide is an important fertilizer.

Uses of Dinitrogen (N2)

• The main use of N2 is in the manufacturing of ammonia. It is also used in the p
  reparation of some other important chemicals such as calcium cyanide, nitric acid, etc.

• It is used for providing an inert atmosphere in several metallurgical operations.

• Liquid nitrogen is used as a refrigerant to preserve biological materials and in freezing food articles. It is also used in cryosurgery.

• It is used as an inert diluent for reactive chemicals.

Industrial Applications of Nitrogen 

The main use of nitrogen in the industrial world is to create ammonia required for explosives, fertilisers, and other materials. However, there are plenty of other uses of nitrogen in different industries. Whether it is pharmaceuticals or food packaging, nitrogen is an essential element in many areas. Mentioned below are the uses of nitrogen in different industries: 

1. Food Packaging

Nitrogen is used in many food production processes to maintain the quality of food or beverage. It has become a common practice for manufacturers to use compressed nitrogen to replace oxygen while packing perishable food items. In the absence of oxygen, food items such as vegetables, fruits, meats, and snacks can last longer. Moreover, nitrogen also prevents food from getting damaged during transport. 

2. Car Tires 

Car tires inflated with nitrogen perform much better than the ones inflated with compressed air. Using nitrogen in your car tires can improve the fuel economy of your vehicle. Unlike compressed air, nitrogen struggles to escape from the tire’s cavity, which ensures that the pressure inside the tire remains the same for a long time. At an ideal pressure, the car’s engine works more smoothly. 

Not only the fuel economy, but nitrogen can also enhance the durability of your car tires. Compressed air contains water vapour that leads to rustiness in the wheels. However, nitrogen eliminates the risk of corrosion and enhances the lifespan of the tire. 

Moreover,  tires inflated with nitrogen offer more safety than the ones that have compressed air in them. No matter what the weather condition is, nitrogen inflated tires are the best choice. These tires ensure consistent performance in dry and wet conditions. If you often drive on highways, nitrogen-filled tires will help you smoothen the ride and improve your driving experience. 

3. Chemical Blanketing 

Many manufacturers use nitrogen in highly explosive chemical plants to displace oxygen from the production process. It is usually used to prevent explosions and fires in a dangerous environment such as factories, manufacturing facilities, and chemical plants. By lowering the level of oxygen, one can prevent explosions in their manufacturing facilities. 

4. Electronics

While assembling electronic devices, nitrogen is used to combine two components of the device permanently. This process is also known as soldering. In this process, nitrogen is used to provide a cleaner break away from the electric bond by reducing the surface tension. Besides this, nitrogen also plays a pivotal role in preventing computers from overheating. 

5. Laboratory

In laboratories, researchers or scientists require a specific environment to carry out tests and results accurately. For this, nitrogen is used to control oxygen levels, temperature, and humidity. This way, the gas helps in maintaining the perfect atmosphere to perform sensitive procedures and tests using heavy equipment. Other than that, many types of lab equipment require nitrogen for purging too. 

6. Laser Cutting 

Since nitrogen can be used for purging, it has become an essential element for the entire steel industry. The nitrogen gas is used to blow away molten residue and help in producing a durable and stronger stainless or aluminised steel product, which is resistant to corrosion.