Ammonia and Nitric Acid

Ammonia and Nitric Acid: Understanding the Basics 

Students may already have been introduced to the compound ammonia, and have some idea about its composition. It is a combination of three hydrogen atoms or molecules and nitrogen. The combination leads to the formation of ammonia gas. Besides this, an understanding of the properties of ammonia is also important. 

We will not go into a relatively elaborate discussion on ammonia but also focus on its important attributes. By the end of this discussion, you will also have an idea about the laboratory preparation of ammonia acid. Do note, this is a vital chapter in your curriculum.

Nature of Ammonia 

Ammonia is also known as nitrogen trihydride or azane. The chemical formula of ammonia is NH3. The molecule has a trigonal pyramidal shape. Three hydrogen atoms are connected with sole nitrogen. The nitrogen atom with a single electron pair makes ammonia to be a base. It can form a homogenous mixture with water and owing to the hydrogen bonds it can form ammonia, which is a polar molecule.

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Within the human body, ammonia occurs naturally. It is secreted by the kidneys which help in the neutralisation of acids within body. Ammonia can also be found naturally occurring in our atmosphere, in volcanic areas, as well as in rainwater in small quantities. 

Structure of Ammonia Molecule 

The molecules of ammonia exhibit a pyramidal shape and the nitrogen atom is placed at the vertex. Ammonia molecules constantly undergo inversion motion wherein the nitrogen atom moves through the plane of a hydrogen atom like an upside down umbrella.

The properties of ammonia that are seen are owing to ammonia acting as a base. The atom of nitrogen may either bond to a metal cation or to a proton such as forming an ammonium ion.  

When the ammonia is frozen or in liquid form, there exists molecular attraction through the shared hydrogen atom between two molecules. Such sharing is called hydrogen bonding. Due to this bond, an association takes place leading to the formation of compounds which contain free electrons that may be obtained by treating ammonia solutions with various complexing agents.

Properties of Ammonia 

The physical properties of ammonia are listed below in detail–

  • Colourless gas having a pungent and suffocating odour.

  • Freezing point is -77.7°C.

  • Boiling point is -33.35°C.

  • Lighter than air given its density to be 0.583 times of air. 

  • Molar mass is 17.03g/mol.

Given the extremely low boiling point of ammonia, liquid ammonia can be readily stored at high pressure and low temperature. In its purest form, anhydrous ammonia can readily absorb moisture (hygroscopic). It also retains alkaline properties and amounts to being corrosive. 

Do You Know?

Research studies have found out that ammonia can have a toxic effect on the glial and nerve cells of the brain. While in healthy people, ammonia is converted into urea in the liver which is eventually washed out with urine, there could be excessive concentration ammonia in blood for people with impaired liver function. The higher levels lead to ammonia toxicity triggering seizures and coma. 

Laboratory Preparation of Ammonia 

Ammonia is prepared by the Haber-Bosch process. The process, in principle, combines nitrogen from the air with that of hydrogen that is mainly derived from natural gas such as methane. It leads to the production of ammonia. The production of ammonia is exothermic, and this reaction is reversible in nature.

In the presence of a metal catalyst, elemental hydrogen and elemental nitrogen are reacted which gives out ammonia gas. The reaction is conducted at very high pressure as well as high temperature (400-550°C). 

N2 + 3H2 → 2NH3

Uses of Ammonia 

  • Ammonia acts as a precursor to different nitrogen compounds like amino acids, urea, phenol, hydrogen cyanide, acrylonitrile, nitric acid, soda ash, among others.

  • It finds extensive usage in the production of polymers, fertilisers, synthetic fibres such as rayon and nylon, cleaning agents, refrigerants along with explosives like nitroglycerin and TNT. 

Even though ammonia is present and finds usage in many household products and purposes; its inhalation can be highly toxic. The fumes of ammonia have a very sharp and pungent odour that can cause irritation in nose, eye, mucous membranes and skin. It can also cause severe damage to the respiratory tract. When exposed to a very high concentration of ammonia gas, it may lead to permanent lung damage or even death. 

Nitric Acid 

Nitric acid (HNO3) is a strong acid which is also known as aqua fortis and the spirit of nitre. It may be decomposed into nitrogen oxides (NOx) and water. Nitric acid further reacts with metals, hydroxides and oxides leading to the formation of nitrate salts. Nitric acid acts as a strong oxidising agent which is used for the catalytic oxidation of ammonia.

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Properties of Nitric Acid 

  • Nitric acid is a fuming, colourless and highly corrosive agent.

  • Freezing point is -42°C.

  • Boiling point is 83°C.

  • PH is approximately 3.01.

  • Nitrogen atom is bonded to a hydroxy group and forms equivalent bonds with the rest oxygen atoms.

  • It is conjugate acid of a nitrate.

Test Yourself 

1. The Factories Producing Fertilisers Need to have Plant(s) of -

(a) ammonium nitrate production.

(b) nitric acid production.

(c) ammonia production.

(d) all of the above.

2. During Ammonia Production, Low Temperature is Maintained. The Benefit of Low Temperature –

(a) better yields only.

(b) better quality.

(c) slow and better yields. 

(d) better quality.

3. _______________ can be Used to Catalyse the Synthesis of Ammonia.

(a) Iron

(b) Nickel 

(c) Platinum 

(d) Aluminium 

Solutions: 1. (d) all of the above 

      2. (c) slow and better yields 

      3. (a) Iron

Laboratory Preparation of Nitric Acid 

Laboratory preparation of Nitric Acid (HNO3) involves heating of nitrate salt with that of concentrated sulphuric acid.

NaNO3 + H2SO4 → NaHSO4 + HNO3

Nitric acid vapour is condensed into brown-coloured liquid within a receiver that is cooled by cold water. The oxides of nitrogen that remain dissolved in the mixture are removed by way of re-distillation.  

Uses of Nitric Acid 

  • Nitric acid has several industrial uses and acts as a building block chemical for many other chemical compounds. It is used for the manufacture of different polymers such as polyurethane and polyamide. 

  • It is used to make explosives such as nitro-glycerine and trinitrotoluene (T.N.T). Nitric acid also finds usage in the aerospace industry as rocket propellant.

  • Nitric acid is used in fertiliser production such as ammonium nitrate, calcium nitrate etc. It is also used in our daily lives as laboratory reagents, for cleaning food and dairy equipment, among others. 

Chemistry can prove to be one of the difficult subjects that you may have to prepare in your syllabus. However, you can join our online classes where even the basics of the subject will be explained along with providing clarification of all your doubts on ammonia and nitric acid formulae properties preparation. 

Various topics, such as properties of ammonia, are frequently touched upon in examination. Hence, when you have a clear understanding of such topics, you can hit the ground running in terms of preparation.

FAQ (Frequently Asked Questions)

1. What are the Properties of Ammonia?

Ans. The physical properties of ammonia are that it is a colourless gas with a sharp odour with its freezing point to be at -77.7°C and boiling point at -33.35°C. Ammonia gas can be liquefied, but on account of its low boiling point, it must necessarily be stored at high pressure and low temperature.

The chemical properties of ammonia are that it is a weak base and can form ammonium salts on combination with different acids. Such chemicals are important for many industries. Liquid ammonia is also a useful non-aqueous solvent dissolving different alkali and alkaline-earth metals producing conductive solutions. 

2. How is Ammonia Prepared?

Ans. Ammonia is prepared commercially by way of Haber-Bosch method where elemental nitrogen and hydrogen undergo reaction in the presence of a metal catalyst emitting ammonia gas. The reaction takes place at high temperature (400-500°C) and high pressure. 

N2 + 3H2 → 2NH3

3. What Kind of Reaction is Ammonia?

Ans. The dissolution of ammonia in water is an exothermic reaction forming an aqueous ammonia solution called ammonium hydroxide (NH4OH).

NH3 + H2O → NH4OH

4. What are the Properties of Nitric Acid?

Ans. Nitric acid (HNO3) is a strong acid which can undergo complete ionisation – hydronium (H3O+) and nitrate ion (NO3-) in an aqueous solution. It acts as a powerful oxidising agent and also decomposes water into oxygen and nitrogen dioxide, leading to a brownish-yellow solution.