Nitrogen Trioxide - N₂O₃

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 degree 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 + NO2 ⇌ N2O3

Properties of Nitrogen Trioxide N2O3

Nitrogen trioxide (molecular formula N2O3) has a molecular weight of 76.012 g / mol and 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 C and -100.7 degree C.

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 Ų

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 purpose 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 to 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 _.

  1. Brown gas, Blue gas

  2. Colourless solid, brown gas

  3. Colourless solid, colourless gas

  4. Blue solid, Brown gas



Dinitrogen trioxide (N2 O3 ) is solid in blue colour. Nitrogen has an oxidation number of +3 while NO2 is a gas in brown colour. The oxidation number of nitrogen in the compound is +4. Therefore, the answer is 4.


Q. Assertion: N2 O3 is Less Basic than P2 O3.

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

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

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

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

  4. 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 decrease 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.

FAQs (Frequently Asked Questions)

Q1. What are the Health Hazards of Nitrogen Trioxide N2O3?

Ans: 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.

Q2. What are the Fire Hazards Caused by Nitrogen Trioxide N2O3?

Ans: 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.