Difference between revisions of "Nitrous acid"

Revision as of 18:43, 18 July 2016

Nitrous acid is a monobasic weak acid, which can only exist in diluted solution and in the salt form (nitrite). It has the chemical formula HNO₂.

Properties

Chemical

Nitrous acid decomposes to release nitrogen oxides:

2 HNO₂ → NO₂ + NO + H₂O

The resulting nitrogen dioxide reacts with water to produce nitric acid.

Physical

Nitrous acid can only exist as solution and as such, all of its properties result from the solution, rather than pure compound.

Availability

Nitrous acid is not sold by chemical entities due to its instability and must be made in situ.

Preparation

Nitrous acid can be prepared by carefully adding a diluted strong acid to a nitrite salt. If the acid is too strong or the addition is too sudden, some of the nitrous acid will rapidly decompose.

3 HX + 3 MNO₂ → 3 MX + HNO₂ + NO + NO₂ + H₂O

Dissolving dinitrogen trioxide in cold water will result in very pure nitrous acid:

N₂O₃ + H₂O → 2 HNO₂

Projects

• Make nitrite salts
• Destroy azides
• Make diazonium salts

Handling

Safety

Nitrous acid is corrosive and it tends to give off nitrogen oxides, which are irritant and toxic.

Nitrous acid explodes in contact with phosphorus trichloride.

Storage

Nitrous acid cannot be stored for long periods of time and has to be made in situ.

Disposal

Nitrous acid can be neutralized with any base. Sodium percarbonate can also be used, as it will oxidize the nitrous acid to nitric acid and the sodium carbonate will neutralize the said acid to harmless sodium nitrate.

References

Relevant Sciencemadness threads

• Nitrous acid production & shelf life