The nitric acid chemical formula is HNO₃. Nitric acid is a strong acid and mostly corrosive and it finds application in the manufacture of fertilizers, explosives, and etching metals.

Physical properties Nitric Acid

Appearance: Pure nitric acid is colorless but owing to its aging and impurities containing NO₂ dissolved in the acid, nitric acid usually appears as yellowish and has a sharp, acrid smell.

State: At room temperature and atmospheric pressure, it is in liquid form.

Density: The concentrated nitric acid possesses a density of about 1.41 g/cm³ at 20°C, but normally the density of nitric acid varies with concentration.

Boiling point: Nitric acid at about 83°C is at its boiling point; this is for concentrated nitric acid. For more dilute solutions, this boiling point can be lower.

Melting point: Nitric acid has a melting point of about -42°C in its pure form.

Solubility in Water: Nitric acid is highly soluble in water in every proportion. In addition to the concentrated nitric acid to water, much heat is produced on account of the heat of the solution liberated during dissolution being exothermic.

Vapor Pressure: Nitric acid possesses a fairly high vapor pressure, especially at high temperatures by which it can evaporate easily into the atmosphere.

Viscosity: The nitric acid is somewhat less viscous than many liquids and thus its flow characteristics are not changed much.

Reactivity: It is corrosive enough to react with practically any type of metal producing metal nitrates and hydrogen gas. The acid also causes severe burns and damage to materials such as glass and certain plastics.

Acidity: Nitric acid is a strong acid; its pH concentration is very low, about 1 or less.

Chemical properties

Acidic Properties

Strong Acid: Nitric acid is a strong acid, completely dissociated in water to produce hydrogen ions or H⁺ and nitrate ions (NO₃⁻).

Reaction with Bases: It reacts with bases to form salts and water.

Oxidizing Agent

Reduction of Metals: Nitric acid is a powerful oxidizer; therefore, it can easily oxidize the major group of metals. For example, it oxidizes copper to copper nitrate, releasing nitrogen dioxide or nitric oxide depending on the concentrations and other conditions.

3Cu+8HNO3→3Cu(NO3)2+2NO2+4H2O

Reaction with Nonmetals: It also oxidizes nonmetals such as sulfur and carbon. Sulfur, for example, reacts to form sulfuric acid.

S+6HNO3→H2SO4+6NO2+2H2O

Nitration Reactions

Nitration of Organic Compounds: Nitric acid is used in nitration reactions - a process where nitro groups are introduced into organic molecules. This has very great importance in the manufacture of explosives such as TNT, and trinitrotoluene, and also in the manufacture of dyes and pharmaceuticals.

C6H6+HNO3→C6H5NO2+H2O

The nitration is done in the presence of sulfuric acid, which acts as a catalyst and dehydrating agent.

Reactions with Carbonates and Bicarbonates

Carbonates: It reacts with carbonates to form carbon dioxide gas, water, and nitrate salt.

HNO3+CaCO3→Ca(NO3)2+CO2+H2O

Bicarbonates: It reacts with bicarbonates to produce carbon dioxide, water, and nitrate salt.

HNO3+NaHCO3→NaNO3+CO2+H2O

Reaction with ammonia

Ammonium Nitrate Formation: Nitric acid is combined with ammonia to form the fertilizer ammonium nitrate and also serves in the production of explosives.

HNO3+NH3→NH4NO3

Decomposition of Concentrated Nitric Acid: Concentrated nitric acid usually decomposes when heated into NO₂, water, and O₂

4HNO3→4NO2+2H2O+O2.

Reaction with Organic Materials

Organic Oxidation: Nitric acid has the capability of oxidizing several organic materials like sugars and cellulose through the formation of carboxylic acids among other oxidation products.

Application Nitric Acid

Ammonium Nitrate: Nitric acid is utilized in the production of ammonium nitrate [NH₄NO₃], which is a major composition of nitrogen fertilizers. This fertilizer has wide applications in soil quality improvement and yield enhancement of crops.

Explosives: Nitric acid is used to produce explosives such as TNT-trinitrotoluene and dynamite. Here, it acts by the nitration of organic compounds to highly reactive explosive materials.

Nitration Reactions: Nitric acid is used as an important intermediate in various chemical syntheses of pharmaceuticals, dyes, and agrochemicals for the manufacture of nitrocompounds.

Nitrocellulose: Its manufacture entails the use of nitric acid, which finds application in lacquers, coatings, and explosives.

Pickling and Etching: Nitric acid is used in picking metals, removing oxides and scale, and in the etching process, which imparts a characteristic pattern of fine detail to the surface of metals. This helps in cleaning and preparing metals for further processing or coating.

Etching: Nitric acid finds its application in the industry of electronics to attain etchings on circuit boards and other electronic parts. It helps in perfecting the patterns by removing unwanted material from the original material.

Pharmaceutical Synthesis: Nitric acid features in the formulation of a wide range of pharmaceuticals and their intermediates. Thus, playing its role in the chemical process leading to the active ingredient in medications.

pH Adjustment: Nitric acid has been applied to various industrial processes for water pH adjustment. It is sometimes used to neutralize alkaline conditions or as part of systems of water treatment.

Analytical Chemistry: It is utilized in the laboratory as a reagent in many forms of chemical analysis, including sample preparation and the detection of certain elements and compounds.

Cleaning and Disinfection: This is used in the production of cleaners for industrial equipment and surfaces that require strong acid cleaning to rid them of residue and contaminants.

Nitrogen Dioxide: Nitric acid has been used in the production of nitrogen dioxide (NO₂), a major reagent in the production of nitric acid itself and in the production of other diverse industries.

Dyeing: It finds its application in dyeing, apart from modification treatment of fibers for property development.

Conclusion

These diversified applications, therefore, establish the importance of nitric acid for industries and the chemical world. Its role as a strong acid, and its capability to act even as an oxidizing agent, makes the substance crucial at places of manufacturing and processing and at times in chemical synthesis.

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