What is Nitrogen Trioxide?

Nitrogen trioxide (molecular formula N2O3) is a chemical compound formed by mercury and chlorine. It is also known as dinitrogen trioxide or nitrogen sesquioxide. The compound is highly toxic and irritates the mucous membranes. Nitrogen trioxide is a blue liquid accompanied by a sharp and unpleasant chemical odour. Density 1.447 g / cm3. Due to the low-boiling point of 3.5 degrees C, the compound is held as a liquid by compression. Partially dissociates into NO and NO2. Strong irritant to skin, eyes and mucous membranes. Vapours are very toxic by inhalation. They are used in special-purpose fuels. The prolonged exposure to heat may cause the container to rupture violently and burst out.

\[NO + NO_{2} \rightleftarrows N_{2}O_{3}\]

Properties of Nitrogen Trioxide N2O3

Nitrogen trioxide (molecular formula N2O3) has a molecular weight of 76.012 g / mol and a density of 1.447 g / cm3. It has a hydrogen bond donor count of 0 while the hydrogen bond donor count is 4. The boiling point and melting point of nitrogen trioxide is 3.5 degrees Celsius  and -100.7 degree Celsius.

Some other properties of nitrogen trioxide N2O3 are mentioned below:

XLogP3-AA – -0.1

Rotatable Bond Count - 0

Exact mass - 75.990892 g / mol

Monoisotopic Mass - 75.990892 g / mol

Topological Polar Surface Area - 75.2 Å2

Heavy Atom Count – 5

Complexity – 50.4

Covalently-Bonded Unit Count – 1

Compound Is Canonicalized – Yes

Solubility in water – Yes

Uses of Nitrogen Trioxide

Properties of Nitrogen Trioxide N2O3 is used in the following ways:

  • Due to its highly explosive nature, it is used as a particular fuel.

  • It supports the only combustion and only helps in burning, but does not burn itself which may ignite substances like wood, paper, oil, clothing, etc.

  • It is a powerful oxidizer.

  • It is combined with other chemical compounds to be used as an oxidizing agent.

  • It is also used in the chemical industry, such as in making nylon, dyes, etc.

Structure of Nitrogen Trioxide

Nitrogen – nitrogen (N – N) bonds are almost the same in length as that in hydrazine, that is, 145 pm.  However, Dinitrogen trioxide has a long N–N bond of 186 pm, which is unusual. Some nitrogen oxides contain long N–N bonds, which include dinitrogen tetroxide (175 pm). The Nitrogen Trioxide molecule has a planar structure and exhibits Cs symmetry. 

It produces unstable nitrous acid (HNO2) when mixed into water. An alternative structure for the true anhydride, i.e. O=N–O–N=O, but this isomer is not observed. If the nitrous acid produced is not used up quickly, then it decomposes into nitric oxide and nitric acid. Sometimes, nitrite salts are produced by adding N2O3 to solutions of some bases like NaOH.

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Solved Examples

Q. Nitrogen Trioxide (N2O3) is/has a _ While Nitrogen Dioxide (NO2 ) is/has a _.

a. Brown gas, Blue gas

b. Colourless solid, brown gas

c. Colourless solid, colourless gas

d. Blue solid, Brown gas


Dinitrogen trioxide (N2O3) is solid in blue colour. Nitrogen has an oxidation number of +3 while NO2 is gas in brown colour. The oxidation number of nitrogen in the compound is +4. Therefore, the answer is 4.

Q. Assertion: N2O3 is Less Basic than P2O3.

Reason: As we go down the group, the metallic nature increases. 

a. The reason is the correct explanation of assertion and both assertion and reason are true.

b. The reason is not the correct explanation of assertion and both assertion and reason are true.

c. The reason is false and the assertion is true.

d. The assertion is not true and the reason is true.

Solution: When we go down the group, atomic radius increases, due to this ionization energy decreases and hence a tendency to lose electrons also increases (i.e., the metallic character is increased).

Since metallic characters increase down the group, the basicity increases down the group.

Hence the order of basicity is N2O3 <P2O3

Therefore, the answer is 1.

Q. What is the Chemical Formula of Nitrogen Trioxide?

Solution: The chemical formula of nitrogen trioxide is N2O3.

Handling and Storage

For non-fire spills and leaks, fully encapsulating, vapour-protective garments should be worn. It is not advisable to touch or walk over spilling material. Keep flammables (oil, wood, paper, etc.) away from the spilt substance. If you can do so without putting yourself in danger, stop the leak. To minimize vapours or deflect vapour cloud drift, use water spray. Allowing water runoff to come into touch with spilt substances is not a good idea. Water should not be directed at the spill or the source of the leak. If at all possible, flip leaky containers so that gas instead of liquid escapes. Prevent access to rivers, sewers, basements, and other restricted locations. Isolate the area till the gas has passed. Make certain that the area is adequately ventilated.

Personal Protection and Exposure Control

Wear self-contained breathing equipment with positive pressure (SCBA). Wear chemical protection clothes that the manufacturer has particularly suggested. It may or may not give any heat protection. Protective apparel worn by structural firefighters provides very limited protection in fire circumstances; it is ineffective in spill scenarios when direct contact with the chemical is possible.

Fire Fighting Measures

These items do not burn but will aid in the combustion process. Allow the fire to burn without being extinguished. If fire must be extinguished, it is best to use water spray or fog. Only water; no dry chemicals, CO2, or Halon®. Make sure that water doesn’t enter the containers. Move containers away from the fire zone if you can do so safely. Damaged cylinders should only be handled by experts. Fight fires from as far away as possible or utilize unmanned hose holders or monitor nozzles. Cool containers with large amounts of water until the fire has been extinguished. Water should not be directed at the source of the leak or safety devices; icing may develop. Withdraw immediately if there is a rising sound from the venting safety mechanisms or if the tank is discoloured. Always keep a safe distance from engulfed-in-fire tanks. For severe flames, use unmanned hose holders or monitor nozzles; if this isn't possible, just leave the area and let the fire burn.

FAQs (Frequently Asked Questions)

1. What are the health hazards of nitrogen trioxide N2O3?

Nitrogen trioxide or nitrogen sesquioxide or Dinitrogen trioxide is a corrosive and highly corrosive compound. It should be handled with care and safety. Special safety measures must be taken while heating the compound. Inhaling it or absorbing it through the skin can be highly dangerous or fatal. It causes firm skin and eye irritation. It gives an irritating, corrosive and toxic gas on heating. It causes severe burn or frostbite and injuries when the liquid form of nitrogen trioxide comes in contact with the skin. Water spray should be used to reduce vapours or drift vapour cloud drift.

2. What are the fire hazards caused by nitrogen trioxide N2O3?

Nitrogen trioxide does not burn itself but will support combustion. Vapours from liquefied gas are initially heavier than air and are spread along the ground. According to the properties of nitrogen trioxide N2O3, it reacts vigorously or explosively with many materials, including fuels, cloth, paper, oil, etc. Some may react violently with air, moist air and water. Cylinders exposed to fire may burst and release toxic, corrosive gas. Containers may explode when heated. Ruptured cylinders may rocket.


We must ensure that medical personnel are aware of the materials involved, and precautions must be taken to protect themselves. The victims must be moved to fresh air. Give artificial respiration if the victim is not breathing. We should not use mouth to mouth respiration. Administer oxygen if breathing is difficult. Remove and isolate contaminated clothing and shoes. In case of contact with the hazardous substance, immediately flush skin or eyes with running water for at least 20 minutes. Keep the victim calm and warm and under observation. Effects of contact or inhalation may be delayed.

3. What are the chemical and physical properties of nitrogen trioxide?

The physical characteristics of the compound are as follows:

Nitrogen trioxide is a blue liquid with a strong, noxious chemical odour. 1.447 g/cm3 density Low-boiling (boiling point 3.5°C) and compressed to keep as a liquid. NO, and NO2 are somewhat dissociated. The skin, eyes, and mucous membranes are all inflamed. Inhalation of the vapours is extremely dangerous. It's a component of special-purpose fuels. When exposed to extreme heat for an extended period, the container may violently burst and rocket.

The chemical characteristics of the chemical compound are as follows:

Chemical formula – N2O3

Molar mass – 96.01

Density – 1.783 g/cm3 (gas), 1.4g/cm3 (liquid)

4. What is the safety measure for nitrogen trioxide?

Ascertain that medical staff are aware of the substance(s) in question and that they are taking procedures to protect themselves. Move the sufferer to a more open area. Artificial respiration should be supplied if the person is not breathing. If the victim swallowed or inhaled the chemical, do not utilize the mouth-to-mouth approach; instead, provide artificial respiration using a pocket mask fitted with a one-way valve or other appropriate respiratory medical equipment. If gases are still suspected, the rescuer should put on a suitable mask or self-contained breathing apparatus. If breathing is difficult, give oxygen. Before removing clothing that has become frozen to the skin, it should be thawed. Remove contaminated clothing and shoes and place them in a separate location. If you come into touch with material, flush your skin or eyes with running water for at least 20 minutes. Maintain the victim's calm and warmth. Keep an eye on the victim. Contact or inhalation effects may be delayed. Symptoms may be delayed if breakdown products are inhaled during a fire. The individual who has been exposed may need to be monitored for 48 hours.

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