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Ammonia |Structure, Properties, Preparation, Uses

Last Updated : 08 Feb, 2024
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Ammonia (NH₃) is a colorless gas with a sharp, pungent odor. It is a compound of nitrogen and hydrogen and plays a crucial role in both the industrial sector and biological processes.

Let’s learn about ammonia in detail, including its structure, properties and uses.

Ammonia

Ammonia is nitrogen and hydrogen-based chemical. It is made up of one nitrogen and three hydrogen atoms. NH3 is its chemical formula.

Formation of ammonia by the decomposition of nitrogenous organic matter urea (NH2CONH2).

NH2CONH2 + 2H2O → (NH4)2CO3 ⇌ 2NH3 + CO2 + H2O

The natural breakdown of animal and plant bodies produces ammonia because the nitrogen compounds present in them decompose as they die or decay, resulting in ammonia. Ammonia can also be found in the soil as an ammonium salt.

Ammonia Structure- NH3

The ammonia molecule is produced when three sp3 hybrid orbitals of nitrogen and three s orbitals of hydrogens collide. A lone pair of electrons occupy the 4th sp3 hybrid orbital of nitrogen. The ammonia molecule has a trigonal pyramidal structure as a result of this.

The H-N-H angle is 107.8 , while the N-H bond length is 101.7 pm. Due to lone pair-bond pair repulsion, which tends to push the N-H bond slightly inwards, the H-N-H bond angle is somewhat less than the tetrahedral angle of 10928′. Ammonia is linked in liquid and solid forms due to hydrogen bonding.

Ammonia Structure

Structure of Ammonia

Formation of Ammonia molecule

Physical Properties of Ammonia

Property Description
Physical State Colourless gas
Odour Distinct pungent odour, known as ammoniacal odour
Density Relative to Air Lighter than air, gathered via air displacement downward
Effect on Inhalation Causes tears to well up in the eyes when inhaled quickly
Liquefaction Conditions Easily liquefies at room temperature under a pressure of 8 to 10 atmospheres
Boiling Point under 1 atm –33.5°C (239.6K)
Enthalpy of Vaporization High (1370J/g), used in ice-making equipment and refrigeration systems
Freezing Point Freezes into a white crystalline solid at –77.8°C (195.3K)
Water Solubility Extremely high; one volume of water dissolves about 1300 volumes of ammonia gas
Collection Method Cannot be collected in water due to its high water solubility

Chemical Properties of Ammonia

  • Ammonia is very soluble in water due to its basic composition. Due to the production of OH ions, its aqueous solution is weakly basic.

NH3(g)+H2O(I) ⇋ NH4OH(aq) ⇋ NH4+(aq)+OH(aq)

Because it is basic, it turns moist red litmus blue and neutralises acids in both dry and wet states, generating their corresponding salts.

NH3+HCl → NH4Cl

2NH4OH+H2SO4 → (NH4)2SO4+2H2O

  • Ammonia functions as a Lewis base due to the existence of a lone pair of electrons on the nitrogen atom. Consequently, it can easily donate its electron pair to establish a coordinate bond with electron-deficient compounds such as BF3 or transition metal cations possessing unoccupied d-orbitals to form complexes. As an example,

Ag+(aq)+2NH3(aq) → [Ag(NH3)2]+(aq)

Cu2+(aq)+4NH3(aq) → [Cu(NH3)4]2+(aq)

Thus, ammonia acts as a ligand.

  • Ammonia is neither a fuel nor a fuel supporter when it comes to combustion. In the presence of oxygen, however, it produces dinitrogen and water.

4NH3+3O2→2 N2+6H2O

  • Ammonia is oxidised to dinitrogen gas when it passes through a solution of calcium hypochlorite (bleaching powder), bromine water, or heated copper oxide.

4NH3+3Ca(OCl)2 → 2 N2+3CaCl2+6H2O

8NH3+3Br2 → N2+6NH4Br

2NH3+3CuO+Heat → 3Cu+N2+3H2O

Ammonia is oxidised to nitric oxide when it is passed through Pt/Rh gauze at 500 K under a pressure of 9 bar with an excess of air. Ostwald’s technique uses this reaction as the starting point for making nitric acid.

Preparation of Ammonia

  • Using a strong base to heat ammonium salts: Ammonia is made on a small scale by heating ammonium salts with a strong base.

(NH4)2SO4 + 2NaOH + Heat→2NH3 + 2H2O + Na2SO 

NH4Cl+KOH+Heat→NH3+H2O+KCl

  • Ammonia is made in the lab by heating a mixture of slaked lime and ammonium chloride.

2NH4Cl+Ca(OH)2+Heat→2NH3+2H2O+CaCl2

  • The hydrolysis of metal nitrides, such as magnesium and aluminium nitride, with water or alkalis, can also yield ammonia gas.

Mg3 N2+6H2O→2NH3+3Mg(OH)2

AlN+3H2O→NH3+Al(OH)3

By passing ammonia gas over quicklime, it is dried (CaO). Because ammonia is a basic gas, it cannot be dried by passing it through concentrated sulphuric acid or phosphorus pentoxide, as it will react with them to generate ammonium sulphate or ammonium phosphate. Calcium chloride cannot be used to dry ammonia gas because calcium chloride creates ammoniates.

Preparation of Ammonia by Haber Process

On a commercial scale, ammonia is manufactured by Haber’s process.

N2(g) + 3H2(g) ⇌ 2NH3(g) ; ΔH=–92.4kJ/mol

This is a reversible, exothermic reaction that occurs when the volume decreases. As a result, according to Le Chatelier’s principle, the best conditions for producing ammonia are:

  1. Low temperature: Because the forward process is exothermic, the generation of ammonia is favoured at low temperatures. The rate of reaction, however, will be slow at low temperatures. The reaction’s optimal temperature has been determined to be around 700K.
  2. High pressure will favour the creation of ammonia since the forward reaction happens with a decrease in volume. At a pressure of 200×105Pa (200 atmospheres), the reaction is normally carried out.
  3. Catalyst: The reaction rate is relatively slow, at roughly 700K. Iron oxide is used as a catalyst, along with a minor amount of K2O and Al2O3. The addition of molybdenum as a promoter improves the efficiency of the catalyst.

Haber’s technique compresses a mixture of N2 and H2 in a 1:3 molar ratio to roughly 200-atmosphere pressure. After cooling, the compressed gases are transported through a soda-lime tower to remove moisture and carbon dioxide. These are then fed into a catalyst chamber containing iron oxide, a small amount of k2O, and Al2O3. When the two gases combine to make ammonia, the chamber is heated electrically to a temperature of 700K. Because the process is exothermic, the heat generated keeps the temperature at the desired level, and no additional electrical heating is necessary.

The gases seeping from the chamber contain around 15–20 % ammonia, with the rest being nitrogen and hydrogen with no reaction. They pass via the condensing pipe, which liquefies the ammonia in the receptor and collects it. The unreacted gases are pumped back to the compression pump, where they are mixed with a new gas combination.

The Haber Process

Uses of Ammonia

The following are some of the many uses for ammonia:

  • In Ostwald’s nitric acid synthesis process.
  • In the manufacturing of sodium carbonate, the Solvay process is used.
  • It’s used in the production of rayon and urea.
  • Ammonium sulphate, ammonium nitrate, urea, diammonium phosphate, and other fertilizers are produced.
  • In ice plants as a refrigerant.
  • Furniture and glass surfaces can be cleaned with it.
  • In the laboratory, it is employed as a solvent and as a reagent.

Frequently Asked Questions on Ammonia

What is the Chemical Formula of Ammonia?

The chemical symbol for ammonia is NH3​. This represents a molecule of ammonia consisting of one nitrogen atom (N) and three hydrogen atoms (H).

What is the Structure of Ammonia?

The structure of ammonia (NH₃) is trigonal pyramidal. This molecule consists of one nitrogen atom (N) at the center with three hydrogen atoms (H) symmetrically spaced around it.

What are Properties of Ammonia?

Ammonia is a colourless gas with a distinctive pungent ammoniacal odour. It is lighter than air and may easily liquefy at room temperature when subjected to a pressure of 8 to 10 atmospheres. Under one atmosphere pressure, its boiling point is –33.5C(239.6K). It serves as a Lewis foundation.

What is the Preparation Method of Ammonia?

Haber’s technology is used to produce ammonia on a commercial basis.

N2 (g) + 3H2 ⇌ NH3 (g)  ; ΔH=–92.4kJ/mol

This reaction is carried out in the presence of iron oxide as a catalyst with a little amount of K2O and Al2O3 at a temperature of 700K and a pressure of 200×105Pa or 200 atmospheres. Molybdenum is utilised as a promoter to improve the catalyst’s efficiency.

What are the Uses of Ammonia?

Ammonia is used as:

  1. In the production of nitric acid by Ostwald’s process, sodium carbonate by Solvay’s process, and rayon and urea by Solvay’s process.
  2. In the production of fertilizers such ammonium sulphate, ammonium nitrate, urea, and diammonium phosphate, among others.
  3. In ice plants as a refrigerant.
  4. As a surface cleaner for furniture and glass.
  5. In the laboratory, it is utilised as a solvent and as a reagent.

What Type of Reaction is the Synthesis of Ammonia by Haber’s process?

Haber’s technique produces ammonia through a reversible, exothermic reaction that results in a drop in volume. We hope you found this ammonia post useful. If you have any questions, please leave a comment below and we will respond as soon as possible.



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