H3PO3 - Phosphorous Acid

What is Phosphorous acid?

Phosphorous acid which is also called phosphonic acid is a colourless oxyacids of phosphorus.

Phosphorous acid is produced in the form of a white volatile powder by the slow combustion of phosphorus. Its salts are called phosphites. It is conveniently prepared by allowing phosphorous trichloride to react with water. In industrial synthesis PCl3 is sprayed into steam at 190oC the heat of reaction is used to distill off the hydrogen chloride and excess water vapour.

Other names – trihydroxy-Orthophosphorus acid

H3PO3 Phosphorous Acid
Density 1.65 g/cm³
Molecular Weight/ Molar Mass 82 g/mol
Boiling Point 200 °C
Melting Point 73.6 °C
Chemical Formula H3PO3

Phosphorous Acid Structure – H3PO3

Phosphorous Acid Structure

Phosphorous Acid Structure – H3PO3

Physical Properties of Phosphorous Acid – H3PO3

Odour Sour odour
Appearance White solid, deliquescent
Covalently-Bonded Unit 1
Hydrogen Bond Acceptor 3
Complexity 8
Solubility Soluble in water

Chemical Properties of Phosphorous Acid – H3PO3

    • Phosphorous acid has strong reducing properties it tends to be converted to phosphoric acid. On being heated dry phosphorous acid disproportionates to give phosphine and phosphoric acid.

H3PO3 + 3H3PO3 → PH3 + 3H3PO4

    • Phosphorous acid reacts with a base like sodium hydroxide forms sodium phosphate and water.

H3PO3 + 3NaOH → Na3PO3 + 3H2O

Uses of Phosphorous Acid – H3PO3

  • Used in the production of basic lead phosphonate PVC stabilizer, aminomethylene phosphonic acid and hydroxyethane diphosphonic acid.
  • Used as a strong reducing agent.
  • Used in the production of raw materials of phosphorous acid, synthetic fibres and organophosphorus pesticides etc.
  • Used in the production of high efficient water treatment agent amino trimethylene phosphonic acid.

Frequently Asked Questions

What is phosphorous acid used for?

Phosphoric fatty acid. Phosphoric acid, also known as orthophosphoric acid, (H3PO4), the most essential phosphorus oxygen acid, was used to produce fertilizer phosphate salts. It is also used in dental cements, in albumin derivatives preparation and in the sugar and textile industries.

Why is phosphorous acid stronger than phosphoric acid?

Hydrogen does not pull on electrons as much as oxygen and thus part of the molecule is more positive, creating a stronger dipole moment in phosphoric acid than that. Phosphorous acid has the constant of higher acidity corresponding to a lower pKa value and is thus more acidic than phosphoric acid.

Which acid is h3po3?

H3PO3 is called orthophosphorous acid or phosphorous acid. It is one of the phosphorus oxygenic acids. Phosphorous acid (H3PO3) forms salts known as phosphites which are sometimes used as reduction agents.

What is the basicity of phosphoric acid?

Phosphoric acid baseline, is 3. Basicity of the molecule is the number of acidic hydrogen atoms. To be acidic, hydrogen must be bound to a highly electronegative atom such as oxygen or fluorine.

What are the side effects of phosphoric acid?

Lips, tongue, throat and stomach will burn. Symptoms may include nausea, vomiting, cramps in the stomach and diarrhoea. May results in permanent damage. Long-Term (Chronic) Effects of exposure: At low concentrations: can cause dry, raw, cracking skin (dermatitis) after skin contact.

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