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Nitric Acid - Structure, Uses, Properties, Preparation, FAQs

Nitric Acid - Structure, Uses, Properties, Preparation, FAQs

Team Careers360Updated on 02 Jul 2025, 04:37 PM IST

What is HNO3?

Nitric acid formula HNO3 is a strong acid. Spirit of Nera and Aqua Fortis are also names commonly associated with it. Pure and uncoloured, it gets a yellowish cast as it ages. Nitrogen oxides and water are formed when nitric acid decomposes. A highly toxic and corrosive substance. Severe burns are caused by it. Nitrate salts are formed when it reacts with hydroxides, metals, and oxides.

HNO3 chemical name is Nitric acid or Chemical formula of nitric acid is HNO3. Oxidizing agents like HNO3 are used in many industrial processes. Catalytic oxidation of ammonia can be used to manufacture it. Chemicals containing this compound are often used in laboratories and are important in industrial processes such as manufacturing explosives and fertilizers. Nitric acid has a PH of roughly 3.01.

Also read -

HNO3 Molecule Structure

3 oxygen atoms are present in each molecule with 1 nitrogen atom and 1 hydrogen atom in each molecule. A double bond exists between both oxygen and nitrogen atoms in HNO3. In addition to being singly bonded to the nitrogen atom, another oxygen atom is also singly bonded to a hydrogen atom. Oxygen atoms with a charge of -1 are single bonded to nitrogen atoms, forming the last oxygen atom of the nitric acid molecule.

A molecule's nitrogen atom has a charge of +1 since it participates in four covalent bonds (with three oxygen atoms). So, the nitric acid molecule has a net charge of 0 (the positive charge on the nitrogen atom cancels out the negative charge on the oxygen atom). Molecular charges can be delocalized due to resonance in these molecules. Here is a diagram of the nitric acid molecule.

Commonly Asked Questions

Q: What is the significance of nitric acid in the nitrogen oxide cycle in the atmosphere?
A:
Nitric acid plays a crucial role in the nitrogen oxide cycle in the atmosphere. It's formed when nitrogen dioxide (NO2) reacts with hydroxyl radicals (OH). This nitric acid can then be removed from the atmosphere through wet deposition (rain) or it can photodissociate back into NO2. This cycle affects air quality, acid rain formation, and atmospheric chemistry.
Q: How does nitric acid interact with amino acids?
A:
Nitric acid can react with amino acids in several ways. It can protonate the amino group, making the amino acid posit
Q: What is the role of nitric acid in the production of nitrobenzene?
A:
Nitric acid is crucial in the production of nitrobenzene through a nitration reaction. Benzene is treated with a mixture of concentrated nitric and sulfuric acids (mixed acid). The nitric acid provides the nitro group (NO2) that replaces a hydrogen atom on the benzene ring, forming nitrobenzene. This is an important industrial process as nitrobenzene is a precursor to many other chemicals.

Sodium Nitrate Fuming

Its density is 1.50g/cm3 and it contains 98% HNO3. The explosives industry frequently uses this grade. The concentration of the anhydrous acid is approximately 21.4 M, and it is not as corrosive or volatile. The reddish-brown colour of RFNA is the result of significant amounts of dissolved nitrogen dioxide (NO2). Red fuming nitric acid has a reduced density of 1.490 g/cm3 due to the dissolved nitrogen dioxide. The addition of hydrogen fluoride (HF) can be used to make an inhibited fuming nitric acid (also referred to as an IWFNA or IRFNA). Metal tanks are coated with this fluoride for corrosion resistance. The flux protects the metal by forming a fluoride layer.

Fuming Nitrate Acid

Commonly Asked Questions

Q: How does nitric acid interact with bases?
A:
Nitric acid, being a strong acid, reacts vigorously with bases in neutralization reactions. It forms nitrate salts and water. For example, with sodium hydroxide: HNO3 + NaOH → NaNO3 + H2O. The reaction is exothermic and goes to completion due to the full dissociation of nitric acid.
Q: What is the significance of nitric acid in forensic science?
A:
In forensic science, nitric acid is used in various analytical techniques. It's used in the digestion of organic materials for metal analysis, in the development of latent fingerprints on metal surfaces, and in the separation of DNA from bone samples. Its strong oxidizing properties make it useful in breaking down complex organic materials.

Nitric acid - HNO3 Laboratory Preparation

The principle

It is possible for a less volatile acid to displace a more volatile acid. The preparation of nitric acid in the laboratory works on this principle.

Illustration

Unlike sulphuric acid, nitric acid has greater volatility. The metal nitrates displace it with sulfuric acid.

Reactants

In a round bottom flask, 50 grams of potassium nitrate (KNO3) is combined with 25 ml of concentrated sulfuric acid (H2SO4). A temperature of about 200°C is maintained without exceeding it, as long as the reactants are not overheated.

Reaction

KNO3 + H2SO4 → KHSO4 + HNO3
(Salts of more volatile acids + fewer volatile acids displaced more volatile acids)

Collection Method

In the diagram, you can see the process of cooling and condensing the nitric acid vapours for collection.

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Nitric acid - HNO3 Physical Properties

HNO3

Nitric acid

Molecular Weight/ Molar Mass

63.01 g/mol

Density

1.51 g/cm³

Boiling Point

83 °C

Melting Point

-42 °C

Commonly Asked Questions

Q: What is the boiling point of nitric acid and why is it significant?
A:
The boiling point of pure nitric acid is about 83°C (181°F). This relatively low boiling point is significant because it means nitric acid can easily vaporize, creating potentially hazardous fumes. It also forms an azeotrope with water at 68% concentration, which boils at 121.9°C (251.4°F).
Q: How does temperature affect the properties of nitric acid?
A:
Temperature significantly affects nitric acid's properties. At higher temperatures, it becomes more volatile and its oxidizing power increases. Conversely, at very low temperatures, it can form a white solid. Temperature also affects its decomposition rate, with higher temperatures accelerating the breakdown into nitrogen oxides and water.
Q: What is fuming nitric acid?
A:
Fuming nitric acid is a solution of nitric acid that contains dissolved nitrogen dioxide. It appears yellow to red and releases reddish-brown fumes of nitrogen dioxide. It is an extremely potent oxidizer and more reactive than regular concentrated nitric acid.
Q: What is the difference between nitric acid and nitrous acid?
A:
Nitric acid (HNO3) and nitrous acid (HNO2) differ in their oxygen content and properties. Nitric acid is a strong acid and powerful oxidizer, while nitrous acid is a weak acid and reducing agent. Nitric acid is stable, while nitrous acid easily decomposes. Nitric acid has nitrogen in the +5 oxidation state, while in nitrous acid it's +3.
Q: How does nitric acid behave differently from other strong acids like hydrochloric acid?
A:
While both are strong acids, nitric acid is also a powerful oxidizing agent due to its high oxygen content. This means nitric acid can oxidize many substances that hydrochloric acid cannot. For example, nitric acid can dissolve copper, while hydrochloric acid alone cannot.

Nitric acid - HNO3 Chemical Properties

  1. Acids such as nitric acid can turn blue when exposed to light.

  2. Nitrogen dioxide is formed by the decomposition of nitric acid. As a result, it turns brown over time, despite being colourless when in its fresh form.
    4HNO3 → 4NO2 + O2 + 2H2O

  3. Nitric acid releases hydrogen gas with metals above hydrogen in the metal activity series.

Mg + 2HNO3 → Mg (NO3)2 + H2
Mn + 2HNO3 → Mn (NO3)2 + H2

Also Read:

HNO3 Structure:

Nitrate Lewis dot structure

Nitric acid: Its Uses

  • Producing ammonium nitrates is used to manufacture plastic, dye, and fertilizer

  • TNT and other explosives are made from it

  • Rockets with liquid fuel use it for oxidation

  • When it is used in its purest form, it helps remove warts

  • Electrochemistry uses it as a chemical doping agent

Also check-

NCERT Chemistry Notes:

Commonly Asked Questions

Q: What are the main uses of nitric acid?
A:
Nitric acid has numerous industrial applications, including: production of fertilizers (e.g., ammonium nitrate), manufacture of explosives (e.g., nitroglycerin), metal etching and cleaning, production of dyes and plastics, and as a key reagent in various chemical processes.
Q: What is aqua regia, and why is nitric acid a key component?
A:
Aqua regia is a mixture of concentrated nitric acid and hydrochloric acid in a 1:3 ratio. Nitric acid is a key component because it acts as a powerful oxidizing agent, which allows aqua regia to dissolve noble metals like gold and platinum that are resistant to other acids.
Q: How does nitric acid contribute to acid rain?
A:
Nitric acid contributes to acid rain when nitrogen oxides (NOx) from various sources react with water vapor and oxygen in the atmosphere. These reactions form nitric acid, which then falls as acid rain, causing environmental damage to ecosystems, buildings, and water sources.
Q: What safety precautions should be taken when handling nitric acid?
A:
When handling nitric acid, important safety precautions include: wearing appropriate personal protective equipment (goggles, gloves, lab coat), working in a well-ventilated area or fume hood, avoiding contact with skin or eyes, never adding water to concentrated acid (always add acid to water), and having proper neutralizing agents and an eyewash station nearby.
Q: How is nitric acid prepared industrially?
A:
Nitric acid is primarily produced industrially through the Ostwald process. This process involves three main steps: 1) Catalytic oxidation of ammonia to form nitric oxide (NO), 2) Further oxidation of NO to nitrogen dioxide (NO2), and 3) Absorption of NO2 in water to form HNO3.

Frequently Asked Questions (FAQs)

Q: Why doesn't nitric acid attack gold and platinum?
A:
Nitric acid alone doesn't attack gold and platinum because these noble metals have high reduction potentials. They are resistant to oxidation by single acids. However, in combination with hydrochloric acid (forming aqua regia), nitric acid can dissolve these metals due to the synergistic effect of both acids.
Q: How does nitric acid react with organic compounds?
A:
Nitric acid reacts with many organic compounds through nitration reactions, where a nitro group (-NO2) is introduced into the molecule. This is important in the production of many explosives, dyes, and pharmaceuticals. It can also oxidize organic compounds, sometimes violently, especially with concentrated acid.
Q: How does nitric acid affect proteins?
A:
Nitric acid denatures proteins by breaking hydrogen bonds and disrupting the protein's secondary and tertiary structures. It also reacts with aromatic amino acids like tyrosine, causing a yellow color. This property is used in the xanthoproteic test to detect the presence of proteins.
Q: How does nitric acid participate in the formation of photochemical smog?
A:
Nitric acid plays a role in photochemical smog formation through its precursor, nitrogen dioxide (NO2). When NO2 is exposed to sunlight, it breaks down to form nitric oxide (NO) and atomic oxygen (O). The atomic oxygen then reacts with molecular oxygen to form ozone (O3), a major component of smog. Additionally, nitric acid can form particulate matter in the air, contributing to smog.
Q: What is the connection between nitric acid and fertilizers?
A:
Nitric acid is crucial in fertilizer production, particularly for nitrate-based fertilizers. It's used to produce ammonium nitrate, a common fertilizer, by reacting nitric acid with ammonia. The nitrate ion from nitric acid provides a readily available form of nitrogen for plants, essential for their growth and development.
Q: How does nitric acid affect the human body upon exposure?
A:
Exposure to nitric acid can severely damage the human body. It causes chemical burns on skin contact, can severely damage eyes, and its fumes can irritate and damage the respiratory system. Ingestion can cause severe internal burns. Long-term exposure to lower concentrations can lead to dental erosion, chronic bronchitis, and increased risk of respiratory infections.
Q: What is the significance of nitric acid in the car industry?
A:
In the automotive industry, nitric acid is used in various processes including metal etching, electroplating, and in the production of certain car components. It's also used in the recycling of catalytic converters to recover precious metals like platinum and palladium.
Q: What is the role of nitric acid in the production of nylon?
A:
Nitric acid plays a crucial role in the production of adipic acid, a key precursor in nylon manufacture. It oxidizes cyclohexane or cyclohexanol to form adipic acid, which is then polymerized with hexamethylenediamine to produce nylon-6,6, one of the most common forms of nylon.
Q: How does nitric acid affect different types of rocks and minerals?
A:
Nitric acid reacts differently with various rocks and minerals. It readily dissolves carbonate rocks like limestone and marble, producing carbon dioxide gas. It can also dissolve some silicate minerals, though less easily. Many sulfide minerals react with nitric acid to produce sulfur dioxide. However, it has little effect on quartz and other resistant minerals.
Q: How does nitric acid contribute to the aging of certain polymers?
A:
Nitric acid can accelerate the aging of certain polymers through oxidation reactions. It can attack the polymer chains, causing them to break or form new cross-links. This can lead to changes in the material's properties, such as becoming brittle, changing color, or losing strength. Polymers with unsaturated bonds or easily oxidizable groups are particularly susceptible.
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