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Oxides of Nitrogen

Last Updated : 24 Feb, 2022
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Nitrogen combines with oxygen to generate nitrogen oxides in a variety of forms. Its oxides have distinct oxidation states, ranging from +1 to +5. Nitrogen oxides with a greater oxidation state are more acidic than those with a lower oxidation state. 

Nitrogen Oxides are a combination of gases that include both nitrogen and oxygen. Nitric oxide (NO) and nitrogen dioxide (NO2) are two of the most toxicologically important chemicals. Nitrogen monoxide (or nitrous oxide, N2O) and nitrogen pentoxide are two more gases in this category (NO5).

The following are examples of nitrogen oxides:

Name of the Oxides of Nitrogen


Oxidation state of Nitrogen

Physical Appearance and Chemical Nature

Dinitrogen Oxide



Colourless gas, neutral

Nitrogen monoxide



Colourless gas, neutral

Dinitrogen trioxide



Blue solid, acidic

Nitrogen dioxide



Brown gas, acidic

Dinitrogen tetroxide



Colourless solid/liquid, acidic

Dinitrogen Pentoxide



Colourless solid, acidic

Nitrogen Dioxide (NO2)

NO2 is the chemical name for Nitrogen dioxide, a highly poisonous gas. Nitrogen (IV) oxide of nitrogen is another name for it. It is a major atmospheric pollutant that absorbs UV light and prevents it from reaching the earth’s surface. Nitrogen (IV) oxide is a yellowish-brown liquid or a reddish-brown gas in its compressed form. When compared to air, its vapours are heavier.

Sources  of Nitrogen dioxide 

Over 98 % of man-made nitrogen emissions are caused by combustion, with the majority originating from stationary sources. Combustion-generated nitrogen oxides are primarily emitted as nitric oxide, a relatively harmless gas that is rapidly converted in the atmosphere to toxic nitrogen dioxide. Nitrogen dioxide is a detriment to human respiratory functions, and prolonged exposure can lead to an increase in the occurrence of respiratory ailments. Nitrogen dioxide is also a precursor in the formation of nitrate aerosols and nitrosamines, both of which are being studied for their potential health effects.

Uses of NO2 

  • In the production of nitric acid, nitrogen dioxide is produced as a byproduct.
  • It is used in the production of oxidised cellulose compounds.
  • As a catalyst, it is used.
  • As an intermediate in the synthesis of sulphuric acid.
  • It is used as an oxidizer in rocket fuels.
  • It’s a nitrating agent.
  • It is used to bleach flour.
  • As an oxidising agent, it is used.
  • Used in the manufacture of explosives.

Health Hazards of NO2 

Severe nitrogen deutoxide exposure can be fatal. When it comes into contact with it, it causes a burning sensation in the eyes and on the skin. It causes frostbite when it is liquid. It has been reported that it reacts with the blood to form methemoglobin. When heated to decompose, it emits toxic nitrogen oxide fumes. At high concentrations, nitrogen dioxide is an irritant gas that causes inflammation of the airways. NO2 primarily affects respiratory conditions that cause severe airway inflammation. Long-term exposure reduces lung capacity, increases the likelihood of respiratory problems, and heightens allergy response. NO2 also contributes to the formation of small particles (PM) and ozone at ground level, both of which have negative environmental consequences.

Nitric Acid (HNO3)

Nitric acid, with the chemical formula HNO3, is a strong acid. It’s also referred to as the spirit of nitre and aqua fortis. It is colourless in its pure form, but as it ages, it takes on a yellow cast. This colour is produced by the decomposition of nitric acid into nitrogen oxides and water. It’s extremely corrosive and toxic. It burns the skin severely. When it reacts with hydroxides, metals, and oxides, it generates nitrate salts.

HNO3 is a powerful oxidizing agent. It can be produced through the catalytic oxidation of ammonia. It is a common reagent used in laboratories as well as an important chemical used in the production of explosives and fertilizers.

Structure of HNO3 Molecules

Nitric acid molecules are made up of three oxygen atoms, one nitrogen atom, and one hydrogen atom. One of the oxygen atoms in HNO3 molecules is doubly bonded to the central nitrogen atom. Another oxygen atom is singly bonded to the central nitrogen atom as well as to a hydrogen atom. The nitric acid molecule’s final oxygen atom has a charge of -1 and is singly bonded to the central nitrogen atom. Because the nitrogen atom in the molecule’s centre is involved in four covalent bonds (with three oxygen atoms), it has a charge of +1. As a result, the net charge on the nitric acid molecule is zero (the positive charge on the nitrogen atom and the negative charge on the oxygen atom cancel each other out). It should be noted that the charges in these molecules can become delocalized as a result of resonance.

Laboratory Preparation of Nitric Acid

A less volatile acid can displace a more volatile acid from its salt. This is the fundamental principle underlying the laboratory preparation of nitric acid. Nitric acid, which is more volatile than sulphuric acid, is displaced from metal nitrates by sulphuric acid. In a round bottom flask, combine 50gm potassium nitrate (KNO3) and 25ml concentrated sulfuric acid (H2SO4). The reactants are heated to around 200 degrees Celsius, being careful not to exceed this temperature.

KNO3 + H2SO4 → KHSO4 + HNO3

Properties of Nitric Acid

  • Nitric acid is a very strong acid that causes blue litmus to turn red.
  • On standing, nitric acid decomposes to form brown nitrogen dioxide. This is why it turns brownish over time, despite the fact that fresh nitric acid is colourless.
  • Nitric acid reacts with metals above hydrogen in the metal activity series to produce hydrogen gas.

Uses of Nitric Acid

  • It is used to make ammonium nitrates, which are then used to make plastic, dye, and fertilizers.
  • It is used in the production of explosives such as TNT.
  • It is used as an oxidizer in liquid-fueled rockets.
  • It is used to remove warts in their purest form.
  • It is used in electrochemistry as a chemical doping agent.

Nitrous Oxide (N2O)

Nitrous oxide (N2O), generally known as laughing gas, is a regularly used anaesthetic and so has a wide range of medical applications. At room temperature, this organic molecule is colourless and non-flammable. It’s also known as laughing gas or nitrous oxide.

Properties of Nitrous Oxide (N2O)

  1. This chemical is insoluble in water and, at higher temperatures, acts as a potent oxidant.
  2. It smells slightly pleasant and appears as a colourless gas.
  3. It produces exhilaration and hilarity when inhaled in little amounts.
  4. It is the world’s most used inhaled anaesthetic because it relieves pain quickly.
  5. At greater doses, it can have a narcotic effect and cause death by suffocation.

Preparation of Nitrous Oxide (N2O)

  • Nitrous oxide is always produced from ammonia nitrate. The cleanliness of the salt must be considered since it should not contain any hydrochlorate or ammonia.
  • It is made by mixing pounded ammonia carbonate with pure nitric acid, which has been diluted with half its volume of water so long as there is effervescence and a tiny amount of carbonate is left in the liquor at the end.
  • The solution has concentrated to the point that its boiling point exceeds 250 degrees Celsius and a drop of it solidifies on a cool glass plate
  • To produce nitrous oxide, a quantity of this salt is placed in a retort and heated with a charcoal coffee, the diffused heat of which is preferable to the heat of the lamp.
  • The salt boils at a temperature of fewer than 340 degrees Celsius and begins to decompose, releasing nitrous oxide and water.
  • Because cold water absorbs much of this gas, nitrous oxide should be collected in a gasometer or a gas holder filled with water that is about 90 degrees. The entire salt decomposes in the same way, and nothing is left in the retort.
  • Nitrous oxide is also created when the salt nitrogen sulphate of ammonia is dissolved in weak nitric acid, however, the following steps do not provide the gas in a pure state.

Uses of Nitrous Oxide (N2O)

  1. As an oxidizer, it is utilised in rocket motors.
  2. It’s used as a food ingredient and as a propellant for aerosol sprays.
  3. It’s a material utilised in the production of semiconductors.
  4. It is used as an analgesic and anaesthetic in medicine.
  5. It is employed as a flavouring agent.
  6. It is used as a fuel additive in motorsports.
  7. It’s a dental filling.
  8. It is used in the production of chemicals.
  9. It’s a surgical instrument.

Nitric oxide (NO)

Nitric oxide, also known as NO, is a colourless gas. 

It is one of the most important nitrogen oxides. Nitric oxide is a free radical, meaning it contains an unpaired electron. Nitric oxide is also a heteronuclear diatomic molecule, a type of molecule studied in the early modern period that gave rise to theories of chemical bonding.

Preparation of Nitric oxide (NO)

In the Ostwald process, nitric oxide is produced commercially by oxidizing ammonia at 750–900 °C with platinum as a catalyst:

4NH3 + 5O2 → 4NO + 6H2O

Commercially, nitric oxide is produced by oxidizing ammonia at 750–900 °C with platinum as a catalyst in the Ostwald process:

N2 + O2 → 2NO

Sample Questions

Question 1: What does nitric acid taste like?


Nitric acid is a strong acid with acidic properties. A pH of less than 7, a bitter taste, and sometimes a violent reaction to other metals are examples of such properties. HNO3 is the chemical formula for nitric acid. Nitric acid is a colourless, white liquid that is extremely corrosive.

Question 2: What metals will nitric acid dissolve?


Nitric acid oxidises some metals and alloys; however, gold and platinum are not oxidised when struck by concentrated nitric acid, and certain metals are passivated. These metals can be dissolved using an acid mixture or a dilute nitric solution.

Question 3: What does nitrogen dioxide do?


The main effect of breathing in high levels of nitrogen dioxide is an increased risk of respiratory disorders. Nitrogen dioxide irritates the lungs’ lining, lowering immunity to lung infections. Wheezing, coughing, colds, pneumonia, and bronchitis can all result from this.

Question 4: Does nitrogen dioxide cause global warming?


The two most toxic and dangerous nitrogen oxides are nitric oxide and nitrogen dioxide. Nitrous oxide, also known as “laughing gas,” is a greenhouse gas that contributes to global warming.

Question 5: Is nitrogen dioxide heavier than air?


Nitric oxide is quickly oxidised in the air at high concentrations to produce nitrogen dioxide. Expositions. Because nitrogen dioxide is heavier than air, it can cause asphyxiation in poorly ventilated, sealed, or low-lying areas. At room temperature, the gases are nitrogen dioxide and nitric oxide.

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