How Nitric Acid (HNO3) Is Used in Everyday Life and Industry
Nitric acid has the chemical formula HNO3 and is a strong acid. It's also known as niter's spirit and aqua fortis. It is colourless in its purest form, but as it ages, it develops a yellow cast. The breakdown of nitric acid into nitrogen oxides and water produces this colour. It's extremely caustic and poisonous. It causes severe burns on the skin. When it reacts with hydroxides, metals, and oxides, it generates nitrate salts.
HNO3 is the nitric acid formula and it is a powerful oxidising agent. It is produced through the catalytic oxidation of ammonia. It's a popular laboratory reagent as well as an important chemical in the manufacture of explosives and fertilisers. Nitric acid has a PH of about 3.01.
Let us know what is HNO3, is nitric acid a strong acid and more details from this article.
Nitric Acid structure
The structure of nitric acid molecules or simply, the nitric acid structure is discussed here.
Three oxygen atoms, one nitrogen atom, and one hydrogen atom make up a nitric acid molecule. One of the oxygen atoms in HNO3 molecules is doubly linked to the central nitrogen atom. A single oxygen atom is singly bonded to the central nitrogen atom, as well as a single hydrogen atom. The nitric acid molecule's last oxygen atom has a charge of -1 and is singly linked to the central nitrogen atom. The nitrogen atom at the centre of the molecule has a charge of +1 because it is engaged in four covalent bonds (with three oxygen atoms). HNO3 is the nitric acid formula.
As a result, the nitric acid molecule has no net charge (the positive charge on the nitrogen atom and the negative charge on the oxygen atom cancel each other out). It should be noted that due to resonance, the charges in these molecules might be delocalized. Below is a diagram illustrating the structure of nitric acid molecules. If we think of nitric acid strong or weak, we can say that it is a strong acid, because It is a powerful oxidising agent that is totally ionised into hydronium (H3O+) and nitrate (NO3-) ions in an aqueous solution.
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Properties of Nitric Acid
Physical properties of Nitric Acid
Nitric acid (HNO3) is a colourless, fuming, and highly corrosive liquid with a freezing point of 42°C (44°F) and a boiling temperature of 83°C (181°F). This is a common laboratory reagent as well as an essential industrial chemical used in fertiliser and explosive production. It's toxic and can cause serious burns. HNO3 chemical name or HNO3 acid name is nitric acid
Chemical Properties of Nitric Acid
Nitric acid is a powerful acid that causes blue litmus to become red.
Standing nitric acid decomposes into brown nitrogen dioxide. This is why, despite the fact that fresh nitric acid is colourless, it turns brown over time.
4HNO3 → 4NO2 + O2 + 2H2O
With metals above hydrogen in the metal activity series, nitric acid liberates hydrogen gas.
Mg + 2HNO3 → Mg(NO3)2 + H2
Mn + 2HNO3 → Mn(NO3)2 + H2
Preparation and Use
The early alchemists were familiar with the preparation and usage of nitric acid. Heating potassium nitrate with concentrated sulfuric acid was a popular laboratory process for many years, credited to a German chemist named Johann Rudolf Glauber (1648). It was discovered to contain oxygen in 1776 by Antoine-Laurent Lavoisier, and its chemical composition was established in 1816 by Joseph-Louis Gay-Lussac and Claude-Louis Berthollet.
Function and use
Other than being starting materials or reagents in chemical and pharmaceutical synthesis, some nitrogen compound types have specific functions.
DMF (dimethylformamide) is a solvent used in the chemical industry to make polyurethanes, methacrylate, and PVC, among other things. Acrylamide is mainly used as a monomer in the production of a wide range of polymeric products. Some epoxy resins contain aromatic amines, but they can also be formed unexpectedly from cleavable azo dyestuff. The majority of azo compounds have vibrant colours. Pesticides such as nitrosamines and thiol amino carbonyl compounds are possible.
Nitric acid breaks down into a brownish-yellow solution that contains water, nitrogen dioxide, and oxygen. It is a powerful oxidising agent and a strong acid that is totally neutralized into hydronium (H3O+) and nitrate (NO3) ions in an aqueous solution (one that acts as an electron acceptor in oxidation-reduction reactions). HNO3 chemical name or HNO3 acid name is nitric acid.
This is a simple explanation for what is HNO3, which is helpful for the students.
Laboratory Preparation of Nitric Acid – HNO3
Principle
A less volatile acid can displace a more volatile acid from its salt. This is the fundamental principle of nitric acid preparation in the laboratory.
Illustration
Nitric acid, a more volatile acid than sulphuric acid, displaces sulphuric acid from metal nitrates.
Reactants
In a round bottom flask, combine 50 g of potassium nitrate (KNO3) and 25 ml of concentrated sulphuric acid (H2SO4). The reactants are heated to around 200°C, with the temperature not exceeding 200°C.
Reaction
KNO3 + H2SO4 → KHSO4 + HNO3
(Salt of more volatile acid + less volatile acid → displaces more volatile acid)
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Method of Collection
As indicated in the diagram, nitric acid vapours are cooled and condensed for collection.
The following are some of the many important reactions of nitric acid.
Neutralization with ammonia to produce ammonium nitrate, which is a major component of fertilisers; nitration of toluene and glycerol to form the explosives trinitrotoluene (TNT) and nitroglycerin, respectively; preparation of nitrocellulose; and also the oxidation of metals either to the corresponding oxides or nitrates.
Hazards of Nitrogen compounds
A large number of the chemicals in this group have the potential to cause cancer. Several are suspected of producing genetic flaws and/or causing fertility problems, while others may harm an unborn child.
Most of them are also considered to be extremely toxic or harmful to aquatic life, and/or extremely toxic or toxic to aquatic life with long-term impacts, and some of them also meet the characteristics of being persistent, bioaccumulative, and toxic (PBT).
Key Nitric acid uses
The important nitric acid uses can be listed as follows:
It's used to make ammonium nitrates, which are used to make plastic, dye, and fertilisers.
It's used to make explosives like TNT.
It is used as an oxidizer in liquid-fueled rockets.
It's used to get rid of warts in their purest form.
In electrochemistry, it is employed as a chemical doping agent.
FAQs on Nitric Acid (HNO3): Properties, Definition, and Uses
1. What is nitric acid and what is its chemical formula?
Nitric acid is a highly corrosive and strong mineral acid, also known as 'aqua fortis'. It is a powerful oxidising agent used widely in industries. Its chemical formula is HNO₃, which indicates that each molecule contains one hydrogen atom, one nitrogen atom, and three oxygen atoms.
2. What are the key physical properties of pure nitric acid?
Pure nitric acid exhibits several distinct physical properties:
Appearance: It is a colourless, fuming liquid in its pure state.
Odour: It has a characteristic sharp, pungent, and suffocating odour.
Nature: It is extremely corrosive to skin and can cause severe burns.
Density: It has a density of approximately 1.51 g/cm³, making it denser than water.
Boiling Point: The boiling point of nitric acid is 83 °C (356 K).
3. What are the major industrial and laboratory uses of nitric acid?
Nitric acid is a crucial chemical with diverse applications. Its most important uses include:
Fertiliser Production: A large percentage of nitric acid is used to manufacture ammonium nitrate, a key component of fertilisers.
Explosives: It is a primary ingredient in the production of explosives such as nitroglycerin and trinitrotoluene (TNT).
Chemical Synthesis: It is used in the nitration process for making various organic compounds, dyes, and polymers like nylon.
Metallurgy: It is used for pickling stainless steel, etching metals, and as a cleaning agent for metals.
Rocket Propellant: In its white fuming form, it is used as an oxidiser in liquid-fuelled rockets.
4. How is nitric acid commercially manufactured?
The commercial production of nitric acid is predominantly done through the Ostwald process, which involves three main steps as per the CBSE syllabus. First, ammonia gas is catalytically oxidised with atmospheric oxygen in the presence of a platinum-rhodium catalyst. Second, the resulting nitric oxide is oxidised further to yield nitrogen dioxide (NO₂). Finally, this nitrogen dioxide is absorbed in water, which results in the formation of nitric acid (HNO₃).
5. Why can nitric acid dissolve most metals, but not noble metals like gold and platinum?
Nitric acid's ability to dissolve most metals, including those less reactive than hydrogen (like copper and silver), is due to its strong oxidising power. It oxidises the metal, allowing it to react and form a soluble salt. However, noble metals like gold (Au) and platinum (Pt) are extremely unreactive and have high electrode potentials, making them resistant to attack by nitric acid alone.
6. Why does concentrated nitric acid turn yellow or brown when exposed to sunlight?
Concentrated nitric acid undergoes photochemical decomposition when exposed to light or heat. The acid slowly breaks down into water, oxygen, and nitrogen dioxide gas (NO₂). The chemical equation is: 4HNO₃ → 2H₂O + 4NO₂ + O₂. The nitrogen dioxide (NO₂) is a reddish-brown gas that dissolves in the remaining acid, imparting the characteristic yellow or brown colour.
7. How does the chemical structure of nitric acid (HNO₃) explain its strong acidic and oxidising properties?
The properties of nitric acid are directly linked to its structure. The nitrogen atom is in its highest possible oxidation state of +5, making it electron-deficient and a very powerful oxidising agent. The molecule is planar, and the highly polar O-H bond allows the acid to readily donate a proton (H⁺) in solution, which is the definition of a strong acid. Resonance stabilisation of the resulting nitrate ion (NO₃⁻) further facilitates this proton donation.
8. What is the fundamental difference between nitric acid (HNO₃) and nitrous acid (HNO₂)?
While both are oxyacids of nitrogen, they differ significantly:
Oxidation State: In nitric acid, nitrogen has an oxidation state of +5, whereas in nitrous acid, it is +3.
Acid Strength: Nitric acid is a strong acid, meaning it fully ionises in water. Nitrous acid is a weak acid and only partially ionises.
Stability: Nitric acid is relatively stable. Nitrous acid is highly unstable and exists only in dilute, cold aqueous solutions.
9. What is the 'passivating' effect, and why does concentrated nitric acid passivate metals like iron?
Passivation is a phenomenon where a metal becomes 'passive' or unreactive towards an acid. When metals like iron (Fe) or aluminium (Al) are treated with concentrated nitric acid, the acid's strong oxidising nature forms a very thin, non-porous, and invisible layer of metal oxide (e.g., Fe₂O₃) on the metal's surface. This protective oxide layer acts as a barrier, preventing the acid from reaching the underlying metal and stopping the reaction.
10. What is 'aqua regia' and what is the role of nitric acid in it?
Aqua regia (Latin for 'royal water') is a highly corrosive mixture of concentrated nitric acid and concentrated hydrochloric acid, typically in a 1:3 molar ratio. Its fame comes from its ability to dissolve noble metals like gold and platinum. In this mixture, the role of nitric acid is to act as a superior oxidising agent that oxidises the gold atoms to form gold ions (Au³⁺). The hydrochloric acid then provides chloride ions (Cl⁻) which react with the gold ions to form a stable complex ion, [AuCl₄]⁻, pulling the gold into the solution.
