Nitric Acid – HNO3

Nitric Acid is a powerful and highly corrosive acid with the chemical formula HNO₃. Nitric Acid is a colorless liquid that can range from pale yellow to reddish-brown due to decomposition into nitrogen dioxide and water. Nitric acid is a key reagent in the chemical industry, playing a crucial role in the production of fertilizers, explosives, and various other chemicals.

Nitric acid (HNO₃) is a strong mineral acid known for its corrosive and highly reactive properties. Nitric Acid is also known as the Spirit of Niter and Aqua Fortis because of its ability to dissolve metals, particularly copper and silver. In this article, we will study in detail about Niitric Acid, the physical, and chemical properties of Nitric Acid, and the different applications of Nitric Acid.

What is Nitric Acid?

Nitric Acid is an inorganic compound having the chemical formula HNO₃. It is known for its corrosive and highly reactive properties. Nitric Acid possesses excellent cleaning properties.

Nitric Acid belongs to the category of a strong acid. In its pure form, it appears colorless and with time, it gets older and hence it turns into the yellow cast. This coloration is happening due to the decomposition of Nitric acid to oxides of nitrogen and water. The nature of Nitric Acid is highly corrosive and toxic. It may cause severe skin burns too. It easily reacts with hydroxides, metals, and oxides to produce nitrate salts. Therefore, it is useful as a strong oxidizing agent.

Nitric Acid Formula

Chemical Formula of Nitric Acid is HNO₃

Molar Mass of Nitric Acid

Molar Mass of Nitric Acid is 63.01 g/mol

Molecular Mass of any compound is calculated by adding the masses of all the constituent atoms. It is the mass of one molecule of a substance.

The molecular mass of HNO3 can be determined as:

• The atomic mass of H = 1u
• The atomic mass of N = 14u
• The atomic mass of O = 16u
• Molecular mass of HNO₃ = 1 + 14 + (16×3) = 63 u

Structure of Nitric Acid (HNO₃) Molecule

The molecular formula of Nitric acid is HNO₃. Nitric acid molecule contain 3 oxygen atoms, 1 nitrogen atom, and 1 hydrogen atom. In its molecules, one of the oxygen atoms is doubly bonded to the nitrogen atom at the centre. Also, another oxygen atom is singly bonded to the central nitrogen atom as well as to the hydrogen atom. The last oxygen atom in the nitric acid molecule is having negative charge of -1 and it is singly bonded to the central nitrogen atom.

Lewis Structure of Nitric Acid

The Lewis structure of nitric acid illustrates the chemical bonding and electron dot structure of the molecule. It shows the covalent bonds formed between the atoms and the distribution of valence electrons. In the case of nitric acid, the nitrogen atom forms a covalent bond with each of the three oxygen atoms, while each oxygen atom forms a covalent bond with a hydrogen atom.

Resonance Structure of Nitric Acid

Resonance structures are a set of two or more Lewis structures that demonstrate the delocalization of electrons in a chemical species. Resonance structures have the same connectivity of atoms, the same number of electrons, and the same chemical formula. The chemical formula of nitric acid is HNO₃.

How to Form Nitric Acid?

The procedure of Nitric Acid Preparation is discussed below:

Principle

A more volatile acid can be easily displaced from its salt through the other one having less volatile acid. This basic principle is very useful in the preparation of nitric acid in the laboratory. This acid is more volatile acidic in comparison to sulphuric acid. Hence, it is generally displaced by the sulphuric acid from metal nitrates.

Preparation Method of Nitric Acid

50gm of the potassium nitrate (i.e. KNO₃ ) and 25ml of concentrated sulphuric acid (i.e. H₂SO₄) is required in a round bottom flask. This set of reactants are heated to about 200 C. But temperature must not be more than 200 C.

Its chemical equation is:

KNO₃ + H₂SO₄ → KHSO₄ + HNO₃

Properties of Nitric Acid

The Properties of Nitric Acid are classified into two categories namely

• Physical Properties of Nitric Acid
• Chemical Properties of Nitric Acid

Physical Properties of Nitric Acid

• Nitric acid is found as a liquid having the acrid, pungent and suffocating odour.
• Its molar mass is 63.01 g/mol and density is 1.51g/cm³.
• Its boiling point is 83°C and its melting point is −42°C.

Chemical Properties of Nitric Acid

• The pH value of Nitric acid is approximately 3.01
• It is highly soluble in water and forms a highly acidic solution when dissolved.
• Nitric acid is a very strong acid, turns blue litmus red.

Nitric Acid Chemical Reactions

Some of the common chemical reactions of nitric acid are:

Reaction with Metals

Nitric acid releases the hydrogen gas with the metals above hydrogen element in the metal activity series. For example-

Mg + 2HNO₃ → Mg(NO₃)₂ + H₂

Mn + 2HNO₃ → Mn(NO₃)₂ + H₂

Reaction with Water

Nitric acid can be decomposed easily to form brown nitrogen dioxide with the help of heat or light.

4HNO₃ + 2H₂O → 4NO₂ + O₂

Reaction with Ammonia

Ammonia on treatment with nitric acid, neutralizes the acid and forms ammonium nitrate.

NH₃ + HNO₃ → NH₄NO₃

Reaction with Sodium Hydroxide

Nitric acid reacts with bases like NaOH to form salts like NaNO₃ and water. This is a neutralization reaction, and it is a common way to prepare nitrates from nitric acid.

NaOH + HNO₃ → NaNO₃ + H₂O

Reaction with Zinc

Zinc reacts with concentrated HNO₃ to form nitrogen dioxide:

Zn + 4HNO₃(conc.) → Zn(NO₃)₂ + 2H₂O + 2NO₂ ↑

Zinc reacts with dilute HNO₃ to form nitrous oxide:

4Zn + 10HNO₃(dil.) → 4Zn(NO₃)₂ + 5H₂O + N₂O ↑

Reaction with Copper

Copper reacts with HNO₃ to form copper nitrate:

Cu + 4HNO₃ → Cu(NO₃)₂ + 2NO₂ + 2H₂O

Nitric Acid Decomposition Reaction

Nitric Acid decomposes into Nitrogen Dioxide which is brown in colour. The decomposition reaction of Nitric Acid is given below:

4HNO₃ → 4NO₂ + O₂ + 2H₂O

Uses of Nitric Acid

The applications of Nitric Acid are mentioned below:

• Nitric Acid is used in liquid-fueled rockets as an oxidizer.
• In its pure form, it is used in the removal of the wart
• Nitric Acid is very and widely used for the production of fertilizers like ammonium nitrate and the polymers like Nylon.
• Explosives like TNT can be produced using Nitric acid.
• Nitric Acid is useful as the chemical doping agent in electrochemistry

FAQs on Nitric Acid

1. How to Identify the Nitric Acid?

Nitric acid is a Liquid that is Colorless to Yellow with a strong, shocky, acidic odor. Concentrated nitric acid will emit the nitrogen dioxide and nitrogen oxide gasses.

2. What Neutralizes Nitric Acid?

Base such as NaOH neutralizes Nitric acid.

3. Can we say that Nitric Acid is a strong acid or not?

Yes. Nitric acid is a type of Strong Acid. It is a strong acid, as almost all of its molecules dissociate into ions in the solution.

4. What are some Health hazards of Nitric Acid?

Nitric acid is the corrosive acid which causes severe Skin Burns Effects.

5. What is pH value of Nitric Acid?

The pH value of Nitric acid is approximately 3.01

6. Does Nitric Acid turn Red Litmus to Blue?

The statement is False. Nitric Acid will not turn the red litmus paper blue. Because Nitric Acid is Acidic in nature and thus, it has no effect on red litmus paper.

7. What is the Chemical Symbol for Nitric Acid?

The Chemical Symbol for Nitric Acid is HNO₃

8. What is the Density and Molar mass of Nitric Acid?

Its molar mass is 63.01 g/mol and density is 1.51g/cm³

9. Why Nitric Acid turns Brown with Time?

Nitric Acid decomposes into Nitrogen Dioxide with time which is basically brown in colour. Hence, Nitric Acid turns Brown with time. The reaction for conversion of nitric acid to nitrogen dioxide is given below:

4HNO₃ → 4NO₂ + O₂ + 2H₂O