Phosphorous pentoxide (P4O10) - Structure, Name, Properties, Molar mass, Uses

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P4O10 compound name

What is Phosphorus Pentoxide (P4O10)?

Phosphorus pentoxide is a chemical compound formed by the combination of four phosphorus atoms with ten oxygen atoms. Its molecular formula is P4O10. As Penta means five, so the name phosphorus pentoxide is derived from its empirical formula, i.e., P2O5.

At ambient temperature conditions, phosphorus pentoxide exists as a crystalline white solid. Chemically, it is a non-metal oxide, also known as an acid anhydride, obtained from phosphoric acid.

In this article, we will talk about everything you need to know about phosphorus pentoxide, including its structure, properties, preparation, and uses. So, continue reading to gain a piece of insightful information about the chemistry behind phosphorus pentoxide (P4O10).

IUPAC name of the chemical compoundPhosphorus pentoxide
Other namesPhosphorus (V) oxide, Phosphoric anhydride
Molecular formulaP4O10
Empirical formulaP2O5
Molar mass283.9 g/mol
Density2.39 g/mL
Type of bondingCovalent bonding

Phosphorus pentoxide (P4O10) structure

Phosphorus pentoxide has a crystalline structure. A large number of P4O10 molecules are held together by weak van der Waals forces of attraction in a symmetrical hexagonal arrangement.

P4O10 structure

Despite the symmetrical arrangement, it is due to the weak forces of attraction between the molecules that P4O10 crystal packing is not a close packing. Instead, it is a stacking of layers, one above the other, as shown in the figure below.

crystalline structure of P4O10

Two types of chemical bonds are present in the P4O10 structure, i.e., a P-O single covalent bond and a P=O double covalent bond. The P-O bond length is 160 pm while the P=O bond is stronger and shorter in length i.e., 143 pm.

There are two different O-P-O bond angles i.e., 102° and 123° in the P4O10 structure.

p4o10 bond angle and bond length

The lewis structure of P4O10 is made up of 4 phosphorous (P) and 10 oxygen (O) atoms. In this structure, 11 single bonds and 4 double bonds are present.

p4o10 lewis structure

Phosphorus pentoxide (P4O10) production  

Phosphorus pentoxide (P4O10) can be prepared by the complete combustion of elemental phosphorus. Burning tetraphosphorus (P4) (also called white phosphorus) in a sufficient supply of oxygen (O2) yields phosphorus pentaoxide (P4O10), as shown in the equation below.  

production of p4o10

Phosphorus pentoxide (P4O10) properties

The most important physical and chemical properties of phosphorus pentoxide (P4O10) are given below.

Physical properties

  • Phosphorus pentoxide (P4O10) exists as a white, crystalline solid in powdered form at r.t.p.
  • It does not possess any distinctive odor.
  • The molecular formula of phosphorus pentoxide is P4O10.
  • The empirical formula of phosphorus pentoxide is a simplified ratio of its molecular formula, i.e., P2O5.
  • The molar mass of P4O10 is 283.9 g/mol.
  • The melting point of P4O10 is 340° C or 613 K.
  • The boiling point of P4O10 is 360° or 633.15 K, at which it sublimes.
  • The vapor pressure of P4O10 is 1 mm Hg at 385 °C in its most stable form.
  • P4O10 is hygroscopic in nature.

properties of p4o10

Chemical properties

  • Phosphorus pentoxide (P4O10) is extremely reactive with water. It undergoes hydrolysis by an exothermic reaction when exposed to water.
  • Phosphorus pentoxide (P4O10) is a covalent molecular compound. The phosphorus (P) and oxygen (O) atoms are held together via strong covalent chemical bonding.
  • The P4O10 molecules are consequently held together by weak Van der Waals forces in a crystalline arrangement.
  • There are four different crystalline forms of P4O10 known as polymorphs.
  • P4O10 is not flammable in nature, but it liberates heat by reacting vigorously with water and water-containing substances like cotton and wood, which may cause a fire.
  • Phosphorus pentoxide is corrosive in nature, especially because it corrodes metals.
  • Contact with a concentration of phosphorus pentoxide as low as 1 mg/m3 can cause serious health implications such as skin, eye, and respiratory tract irritation.

Phosphorus pentoxide (P4O10) uses

  • Phosphorus pentoxide (P4O10) is used as a dehydrating agent in the chemistry laboratory.
  • P4O10 is used for the production of phosphoric acid in the chemical manufacturing industry. The exothermic hydrolysis of P4O10 yields H3PO4.

reaction of p4o10

  • Phosphorus pentoxide is used in organic synthesis. For instance, nitriles (R-CN) can be prepared by heating primary amides (R-CONH2) with P4O10.
  • P4O10 is used in a granular form in the desiccators. As it is a powerful dehydrating agent, so it forms a viscous coating and protects moisture-sensitive materials, stored in the desiccator.
  • Phosphorus pentoxide is used for the synthesis of anhydrides [RC(O)]2O by reacting with carboxylic acids (RCOOH).
  • It is also used for the oxidation of alcohols as the main component of Onodera reagent (the solution of P4O10 in DMSO).
  • Phosphorus pentoxide (P4O10) can be used to prepare crop fertilizers in the agricultural sector since it contains phosphorus (P) which is vitally essential for plant growth.


How to write the name for P4O10?

What is P2O5 called?

P2O5 is the empirical formula for phosphorus pentoxide (P4O10) which is also known as phosphorus (V) oxide, diphosphorus pentoxide, tetraphosphorus decoxide, and phosphoric anhydride.

How is P2O5 named phosphorus pentoxide?  

P2O5 is a binary chemical compound as it is composed of two different elemental atoms, i.e., phosphorus (P) and oxygen (O).

For every 2 phosphorus atoms, 5 oxygen atoms are bonded in the crystalline structure of P2O5. Penta is a Greek word that literally means five (5).

The alphabet ‘a’’ in Penta is omitted when it comes before o, such as before oxide; therefore, the name phosphorus pentoxide is given to P2O5.

What is the difference between P2O5 and P4O10?

P2O5 is the empirical formula for phosphorus pentoxide, while P4O10 is its molecular formula. The empirical formula of a chemical compound is the simplified ratio of all the elements present in it. 4:10 in its lowest possible/ simplest form is 2:5.

What is the structure of phosphorus pentoxide (P4O10)?  

Phosphorus pentoxide (P4O10) has a crystalline structure. The covalently bonded molecules are stacked onto one another in a layered arrangement and held together via Van der Waals’s intermolecular forces of attraction.

Is phosphorus pentoxide (P4O10)  soluble in water?   

Yes. Phosphorus pentoxide (P4O10)  is extremely hygroscopic and thus reacts vigorously and exothermically with water, releasing a tremendous amount of energy.

Is phosphorus pentoxide (P4O10)  acidic or basic?   

Phosphorus pentoxide (P4O10) is a non-metal oxide. It is acidic in nature. It reacts vigorously with water and produces orthophosphoric acid (H3PO4).

How can phosphorus pentoxide (P4O10)  be dehydrated?   

Phosphorus pentoxide (P4O10) is already dehydrated. Instead, the phosphoric acid produced by the hydrolytic reaction of P4O10 can be dehydrated at 176°C to yield a mixture of orthophosphate, pyrophosphate, and triphosphate.

What are the oxidation states of phosphorus (P) and oxygen (O) in phosphorus pentoxide (P4O10)?

The phosphorus (P) atom has a +5 oxidation state, while the oxidation state of oxygen (O) is -2 in phosphorus pentoxide.

2(+5) = + 10 cancels with 5(-2) =-10 therefore no formal charge on P2O5. Thus, P2O5 is a neutral molecule overall.

oxidation state in p4o10

How many moles are there in phosphorus pentoxide?   

The empirical formula of phosphorus pentoxide (P2O5) represents 1 mole of the compound. P2O5 is derived from the molecular formula P4O10. One mole of P2O5 represents 141.94 grams of it.

What is the molar mass of phosphorus pentoxide (P4O10)?   

The experimentally determined molar mass of phosphorus pentoxide is 283.9 g/mol. Additionally, its molar mass can also be determined from its molecular formula, i.e., P4O10, as follows:

Molar mass =  4(31) + 10 (16) = 284 g/mol.

Is P4O10 organic or inorganic?   

Phosphorus pentoxide (P4O10) is inorganic in nature. It is composed of two different non-metal elemental atoms, i.e., phosphorus (P) from Group V A (or 15) of the Periodic Table, while oxygen (O) from Group VI A (or 16).

What is P4O10 used for?   

Phosphorus pentoxide (P4O10) is used:

  • As a dehydrating agent.
  • As a desiccant to preserve moisture-sensitive materials.
  • For the production of phosphoric acid by reacting with water.
  • In organic syntheses, such as for the synthesis of nitriles from primary amides and the synthesis of anhydrides from carboxylic acids.
  • For oxidation of alcohols, in the form of Onodera reagent.
  • As crop fertilizer.


  • Phosphorus pentoxide (P4O10)  is a covalent chemical compound.
  • It exists as a crystalline white solid under ambient temperature conditions.
  • The molecular formula for the most stable crystalline form of phosphorus pentoxide is P4O10.
  • Its empirical formula is P2O5.
  • It is produced by heating white phosphorus in a sufficient supply of oxygen.
  • P4O10 reacts vigorously with water and forms orthophosphoric acid by releasing energy.
  • It is a valuable chemical compound as it is used as a dehydrating agent, a desiccant, a reagent in organic syntheses, for fertilizer manufacturing, etc.

Reference –

1. Phosphorus pentoxide (P4O10)  –

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