Nitric Acid (HNO₃): Properties, Structure, Uses, Preparation and Applications Explained

Nitric acid is one of the most important mineral acids used in chemistry and industry. It is a highly corrosive and strong acid with the chemical formula HNO₃. What's interesting is! Pure nitric acid is colourless, but it often appears yellow because of dissolved nitrogen oxides formed during decomposition.

 But have you ever wondered why nitric is considered to be so important? This acid plays a major role in the manufacture of fertilizers, explosives, dyes, medicines, and several industrial chemicals. It is also widely used in laboratories as a chemical reagent and oxidising agent. 

The article is all about the structure, properties, preparation, reactions, uses, advantages, and safety measures related to nitric acid explained in a student friendly way.

Table of Contents 

• What is Nitric Acid
• Difference Between Concentrated and Dilute Nitric Acid
• Properties of Nitric Acid
• Preparation of Nitric Acid
• Uses of Nitric Acid
• Safety Precautions While Handling Nitric Acid

What is Nitric Acid?

Nitric acid is a strong inorganic acid composed of hydrogen, nitrogen, and oxygen. It is commonly known as aqua fortis or spirit of nitre.

When it comes to the Chemical Formula and Structure of Nitric Acid 

The molecular formula of nitric acid is: HNO3

Nitric acid contains:

• One hydrogen atom
• One nitrogen atom
• Three oxygen atoms

On observation the nitrogen atom is bonded to three oxygen atoms, forming a trigonal planar structure. One oxygen atom is attached to hydrogen, forming a hydroxyl group (-OH).

Structural Formula of Nitric Acid:

O=N-(OH)=O

This above structure explains why nitric acid easily releases hydrogen ions in water, making it a strong acid.

Lets discuss the Nitric acid behaviour?

Nitric acid is highly soluble in water and acts as a powerful oxidising agent. It reacts with metals, metal oxides, and bases to form nitrate salts. Because of its reactive nature, nitric acid is widely used in industries and laboratories.

Interestingly! Pure nitric acid is a colourless liquid, but prolonged storage causes it to turn yellow due to the formation of nitrogen dioxide gas.

Lets Discuss how to differentiate between Concentrated and Dilute Nitric Acid! 

Difference Between Concentrated and Dilute Nitric Acid

Basis	Concentrated Nitric Acid	Dilute Nitric Acid
Strength	More acidic and reactive	Less reactive
Appearance	Yellowish due to dissolved gases	Mostly colourless
Oxidising Ability	Stronger oxidising agent	Comparatively weaker
Uses	Industrial manufacturing	Laboratory experiments

Read More: Neutralisation Reaction 

Properties of Nitric Acid

Property	Description
Chemical Formula	HNO₃
Molecular Mass	63 g/mol
Appearance	Colourless or yellowish liquid
Odour	Sharp and pungent smell
Nature	Highly corrosive
Solubility	Completely soluble in water
Boiling Point	83°C
Density	About 1.51 g/cm³
Acid Strength	Strong acid

Chemical Properties of Nitric Acid

Let's Discuss !!

Nitric acid shows several important chemical properties because it is both a strong acid and a strong oxidising agent.

1. Acidic Nature

Nitric acid ionises completely in water to produce hydrogen ions.

HNO3→H++NO3−

Because of complete ionisation, nitric acid is classified as a strong acid.

2. Reaction with Metals

Nitric acid reacts with metals to form nitrate salts. Unlike many acids, it usually does not release hydrogen gas because of its oxidising nature.

Example:

Cu+4HNO3→Cu(NO3)2+2NO2+2H2O

The fact that Copper reacts with concentrated nitric acid to produce copper nitrate, nitrogen dioxide, and water.

3. Reaction with Bases

Nitric acid reacts with bases to form salts and water.

Example:

HNO3+NaOH→NaNO3+H2O

This is a neutralisation reaction.

4. Strong Oxidising Agent

Nitric acid can oxidise many substances easily. This property makes it useful in industries and laboratories.

Preparation of Nitric Acid

Nitric acid is mainly manufactured using the Ostwald Process. This industrial process converts ammonia into nitric acid.

Steps in the Ostwald Process: 

Step 1: Oxidation of Ammonia

4NH3+5O2→4NO+6H2O

Ammonia reacts with oxygen in the presence of a platinum catalyst.

Step 2: Formation of Nitrogen Dioxide

2NO+O2→2NO2

Nitric oxide further reacts with oxygen.

Step 3: Formation of Nitric Acid

4NO2+O2+2H2O→4HNO3

Nitrogen dioxide dissolves in water to form nitric acid.

Uses of Nitric Acid

• Nitric acid has a wide range of industrial, laboratory, and commercial applications.
• Nitric acid is widely used in the manufacture of fertilizers such as ammonium nitrate and calcium nitrate.
• It is used in producing explosives like TNT and nitroglycerin.
• Nitric acid helps in manufacturing polymers, dyes, paints, and medicines.
• It is used for metal cleaning and refining precious metals like gold and silver.
• In laboratories, nitric acid is commonly used as a chemical reagent and for chemical analysis.

Safety Precautions While Handling Nitric Acid

Nitric acid is highly corrosive and dangerous if handled improperly. Proper safety measures should always be followed.

Below are some Important Safety Measures : 

• Wear gloves and protective goggles
• Avoid direct skin contact
• Use in well-ventilated areas
• Store in tightly closed containers
• Keep away from combustible materials
• Wash immediately with water in case of accidental contact

Learn More:  Acid- Base Difference and Acid-Base Titrations 

As we have learned that Nitric acid is one of the most widely used and industrially important mineral acids. Its strong acidic and oxidising properties make it useful in the manufacture of fertilizers, explosives, dyes, polymers, and many industrial chemicals. It also plays an important role in laboratories and chemical analysis. Although nitric acid is highly useful, it must be handled carefully because of its corrosive and toxic nature.