Nitrous Acid: Preparation, Formula, uses, Solubility | Is nitrous acid dangerous?
Nitrous acid

Nitrous Acid: Preparation, Formula, uses, Solubility | Is nitrous acid dangerous?

Chemical Formula

  • Stannic Chloride – SnCl4
  • Stannous Chloride – SnCl2
  • Ferrous Sulfate – FeSO4
  • Hematite – Fe2O3
  • Silicon Dioxide – SiO2
  • Magnesium Carbonate – MaCO

Nitrous acid is a temporary additive. It is not found in an independent state. Its aqueous solution can be obtained at low temperatures. It continues to decompose slowly even at room temperature.

Therefore, to be used in other reactions, first make its solution at low temperature and immediately after that.

Preparation of Nitrous Acid

Nitrous acid is obtained by the action of dilute HCl or H2SO4 on any nitrite.

KNO2 + HCl KCl + HNO2

NaNO2 + HCl NaCl + HNO2


Nitrous acid is obtained when di-nitrogen tri-Oxide is dissolved in cold water.

N2O3 + H2O 2HNO2

HNO2 is obtained by the action of barium nitrite and cold and dilute H2SO4.

Ba(NO2)2 + H2SO4 BaSO4 + 2HNO2

This reaction is used in the laboratory method of making nitrous acid.

Barium sulfate is filtered and separated and remains in HNOsolution.

Physical Properties

The color of its aqueous solution is light blue.

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Chemical Properties

Decomposition: Anhydrous nitrous acid is temporary and decomposes into NO, NO2 and H2O.

2HNO2 NO + NO2 + H2O

It slowly decomposes in aqueous solution –

3HNO2 2NO + H2O + HNO3

In aqueous solution, its decomposition speed is higher at low temperature and high at high temperature.

Acidic Properties: Nitrous acid is a weak acid, it reacts with alkalis to form salts called nitrous salts.

HNO2 + NaOH NaNO2 + H2O

Oxidizing Properties: In the presence of catabolizes, it decomposes and produces nascent oxygen.

For this reason it is a strong oxidizer.

2HNO2 2NO + H2O + O

This iodine is released from any iodide salts in the presence of dilute H2SO4.

2KI + H2SO4 + 2HNO2 2NO + I2 + K2SO4 + 2H2O

This oxidizes stannous chloride to stannic chloride.

SnCl2 + 2HNO2 + 2HCl SnCl4 + 2H2O + 2NO

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