Chemistry Formulas

Hypophosphoric Acid Formula

Hypophosphoric acid is a mineral acid which has a formula of H4P2O6. The phosphorous is in a formal oxidation state of +4. Moreover, in the solid-state, it exists as the dihydrate, H4P2O6·2H2O. If we look at the Hypophosphoric acid formula, we see that the phosphorous atoms are alike and the P-P bond joins it directly. Moreover, the isomeric form isohypophosphoric acid has got a different structure that has phosphorous atoms which do not look alike. One of them already bonds with H atom and an oxidation state of +3 that gets joined by a P-O-P bridge to the second phosphorous atom, having an oxidation state of +5.


Hypophosphoric acid consists of oxonium ions and is best formulated [H3O+]2 [H2P2O6]2−. It is isostructural with diammonium salt that consists of the [HOPO2PO2OH]2− anion with a P−P bond length of 219 pm.

The HOPO2PO2OH2− anion in Na2H2P2O6·6H2O has got asymmetric, staggered structure, which is similar to that of ethane. Moreover, it has got a P−P bond of length 219 pm. Each phosphorus atom has two P−O bonds with length 151 pm and a P−OH bond length of 159 pm.


One can prepare Hypophosphoric acid by reacting red phosphorous with sodium chlorite at room temperature.

2 P + 2 NaClO2 + 2 H2O → Na2H2P2O6 + 2 HCl

When white phosphorous partially immerse in water, it oxidises in the air which results in creating a blend of Hypophosphoric acid and, phosphorous acid and phosphoric acid.

Hypophosphoric acid is unbalanced in hot hydrochloric acid, in 4 M HCl it hydrolyses to give H3PO3 + H3PO4.

Physical Properties & Chemical Properties

We also refer to Hypophosphoric acid as Disphosphoric acid. It has an appearance which looks like white colour and is in solid form. The chemical formula of the same is H4O2P6. Other than that, if we talk about the melting point, we see that it is 54 °C. Similarly, the molar mass of Hypophosphoric acid is 161.98 g/mol. It is also soluble in water.


Hypophosphoric acid has got many uses. It can be used as a bleaching agent and one may also use it as a reducing agent. Other than that, it also works great as a wetting agent. Not only that, but it also has application as a stimulant in pharmaceutical agents.

Health Effects

Hypophosphoric acid is a corrosive liquid. It can result in chemical burns to the skin and eyes. Moreover, if anyone inhales it, it may cause irritation in the upper respiratory tract. Not only that, it can cause irritation in the eye and eyelids. It is advised to always use water to remove it. If not done on time, it can result in prolonged or permanent visual impairment. Also, avoid ingestion as it will cause injury to the mucous lining of the mouth in addition to the throat, oesophagus and the stomach.

Solved Question for You

Question- What is the chemical formula for Hypophosphoric acid?

a) H2O4

b) H4O2P6

c) O2H

d) HOO2

Answer- The correct answer is option B.

Share with friends

Customize your course in 30 seconds

Which class are you in?
Get ready for all-new Live Classes!
Now learn Live with India's best teachers. Join courses with the best schedule and enjoy fun and interactive classes.
Ashhar Firdausi
IIT Roorkee
Dr. Nazma Shaik
Gaurav Tiwari
Get Started

Leave a Reply

Notify of

Customize your course in 30 seconds

Which class are you in?
No thanks.