A Brief note on Nitric Acid

To the early alchemist, the development of nitric acid and its use was mainly known. In 1648, German chemist, Johann Rudolf Glauber ascribed a common laboratory process that was used for many years, the laboratory mainly consisted of heating potassium nitrate along with concentrated sulfuric acid. 

Antoine-Laurent Lavoisier, a chemist of 1776 showed that the development of nitric acid contained oxygen, and during the year 1816 Joseph-Louis Gay-Lussac and Claude-Louis Berthollet discovered nitric acid’s chemical composition. Nitric acid can be prepared in many ways but the scientists later developed a process in which ammonia was used to obtain nitric acid, the principal method of manufacture of nitric acid is ammonia is used as a source of catalytic oxidation. 

In 1901, in the method discovered by the German chemist Wilhelm Ostwald, with the help of a platinum gauze catalyst ammonia gas is oxidised successfully to nitric oxide and nitrogen dioxide with the help of air or oxygen. The nitrogen dioxide compound is absorbed in water to produce nitric acid which results in an acid-in-water solution that is about 50–70 percent the weight of acid, this acid can be dehydrated by distillation with the help of sulfuric acid. Nitric acid is observed to decompose into the water, nitrogen dioxide, and oxygen, forming or leaving a brownish-yellow solution. 

Structure of Nitric Acid Molecules

The chemical formula of Nitric acid is  HNO3. In the structure of Nitric Acid one molecule contains 3 oxygen atoms and 1 nitrogen atom, and 1 hydrogen atom. In nitric acid’s molecules, one of the oxygen atoms is bonded in a double form to the nitrogen atom at the centre. Also, another oxygen atom is bonded in a single form to the central nitrogen atom as well as to the hydrogen atom. 

The last oxygen atom in the nitric acid molecule consists of having a negative charge of -1 and the last oxygen atom is singly bonded to the nitrogen atom present at the central position. As the nitrogen atom is present at the centre in four covalent bonds of the molecule that participates for example with three oxygen atoms. So, the molecule consists of a charge of the positive value of +1. 

However, this results in the net charge present on the nitric acid molecule becoming zero, because of the positive charge possessed by the nitrogen atom and the negative charge possessed by the oxygen atom, both these charges possessed by the nitrogen and oxygen atom cancel each other out. It is further known that the charges in these molecules can be transferred and changed due to the resonance effect; this process also explains the development of nitric acid.

The Nitric acid molecule is planar in shape, with three oxygen atoms attached to the nitrogen atoms, one of which is in charge of holding the proton. The other two N-O bonds are equivalent in form and the resonance is visible or shown with a double bond character.

Physical and chemical properties of nitric acid

• Physical properties

• Nitric acid is mainly found in a liquid state having an odd, pungent, and suffocating odour.
• Various concentrations of nitric acid are available on our earth. These variations are usually colourless or maybe yellow or red according to their respective concentration.
• The industrial grade of nitric acid is approximately 68% in water and the grade is approximately between 52% and 68% commercially.
• Also, the concentration grade of the fuming nitric acid is approximately 86% or maybe higher, however, concentrations of white fuming or red fuming nitric acid are above 95%. The approx PH value of Nitric acid is  3.01.
• The molar mass of nitric acid is 63.01 g/mol and its density is 1.51g/cm3.
• As already mentioned earlier the boiling point of nitric acid is  83C and its melting point is −42C.

• Chemical properties

• The nature of Nitric acid is strong and it is a monoprotic acid.
• Due to its pH scale, the nitric acid turns blue litmus red. It also frequently produces solid hydrates, for example, monohydrate HNO3⋅H2O and also trihydrate HNO3⋅3H2O.
• Nitric acid can be decomposed easily to form brown nitrogen dioxide with the help of heat or light. Nitric acid becomes brownish over time though fresh nitric acid is colourless mainly due to this reason.
• This chemical reaction for the above-mentioned phenomenon is 4HNO3→2H2O + 4NO2 + O2

Also responsible for the development of nitric acid.

• Nitric acid also comprises the nature of a powerful oxidising agent and it also reacts violently or vigorously with many non-metallic compounds. When reacted with metals, these metals dissolve in them to produce metal oxides.
• Hydrogen gas is released from nitric acid due to which it developed a process in which ammonia was used to obtain nitric acid, the metals above hydrogen element 0 in the metal activity series. 
• Some reactions showing the process are :
• Mg + 2HNO3→Mg(NO3)2 + H2
• Mn + 2HNO3→Mn(NO3)2 + H2.

Uses of nitric acid

• The use of Nitric acid is varied in such different forms and also is widely used for the production of fertilisers, for example, ammonium nitrate and the polymers like Nylon.
• It is also used as an excellent nitrating agent which introduces a nitro group when the sulfuric acid is combined. Also, it is useful as an oxidizer in liquid-fueled rockets.
• In the production of the ammonium nitrates for further manufacturing of plastic, dye, and fertilisers, nitric acid is also used.
• Nitric acid produces explosives like TNT.
• When nitric acid is in its pure form, it helps greatly to remove the wart.
• In electrochemistry, It is also very useful as a chemical doping agent.

Conclusion

In 1901, in the method discovered by the German chemist Wilhelm Ostwald, with the help of a platinum gauze catalyst ammonia gas is oxidised successfully to nitric oxide and nitrogen dioxide with the help of air or oxygen. 

The nitrogen dioxide compound is absorbed in water to produce nitric acid which results in an acid-in-water solution that is about 50–70 percent the weight of acid, this acid can be dehydrated by distillation with the help of sulfuric acid. 

Nitric acid is observed to decompose into the water, nitrogen dioxide, and oxygen, forming or leaving a brownish-yellow solution. Which forms a strong acid, completely ionised into hydronium chemical formula H3O+ and nitrate chemical formula NO3− ions in aqueous solution, it also forms a powerful oxidising agent, the oxidising agent that acts as electron acceptor mainly in oxidation-reduction reactions.