What is Phosphorus Pentoxide?
Phosphorus Pentoxide is a chemical compound whose empirical formula is P2O5 and whose molecular formula is P4O10.
At ambient temperatures, this compound exists as a white solid that is crystalline in nature. Phosphorus pentoxide is an acid anhydride that is obtained from phosphoric acid. It is highly hygroscopic and is, therefore, used as a dehydrating agent and as a desiccant.
Table of Contents
- Preparation of Phosphorus Pentoxide
- Structure of Phosphorus Pentoxide
- Properties of Phosphorus Pentoxide
- Uses of Phosphorus Pentoxide
- Frequently Asked Questions – FAQs
Preparation of Phosphorus Pentoxide
P2O5 (or P4O10) can be prepared by burning elemental P4 (tetra-phosphorus) in an environment containing a sufficient amount of oxygen. The chemical reaction for the preparation of P2O5 is provided below.
P4 + 5O2 → P4O10
This compound is a source of pure phosphoric acid.
Structure of Phosphorus Pentoxide
The structure of a phosphorus pentoxide molecule is illustrated below.
It can be noted that the P=O bond length in this compound is 143 picometers and the P-O bond length is 160 picometers.
Properties of Phosphorus Pentoxide
Physical Properties of Phosphorus Pentoxide
- Phosphorus pentoxide is a white solid which does not have any distinct odour.
- The chemical formula of this compound is P4O10. However, it is named after its empirical formula, which is P2O5.
- The molar mass of phosphorus pentoxide corresponds to 283.9 g/mol.
- The density of this solid is 2.39 g/cm3.
- The melting point of this P2O5 is 613K. Its boiling point corresponds to 633K (however, it undergoes sublimation at this temperature).
Chemical Properties of Phosphorus Pentoxide
- Phosphorus pentoxide undergoes violent hydrolysis when exposed to water. This reaction is highly exothermic.
- This compound crystallizes in four different polymorphs.
- It is highly corrosive and must, therefore, be kept away from metals.
Uses of Phosphorus Pentoxide
- This compound is a very potent dehydrating agent (since it undergoes hydrolysis in an exothermic manner).
- Phosphorus pentoxide is also used in some organic synthesis reactions. For example, it is used in the preparation of nitriles from primary amides.
- It is a vital component of the Onodera reagent, which is widely used in the oxidation of alcohols.
- This compound can also be used to convert certain mineral acids into their anhydrides. For example, N2O5 can be prepared from HNO3 with the help of P2O5.
Frequently Asked Questions – FAQs
Is P2O5 an acid?
Phosphorus pentoxide is an acidic oxide and it is used as a desiccating and dehydrating agent because it is an anhydride of phosphoric acid.
Is P2O5 a phosphate?
Phosphorus pentoxide is a chemical compound with molecular formula P4O10 (with its common name derived from its empirical formula, P2O5). This white crystalline solid is the anhydride of phosphoric acid. It is a powerful desiccant and dehydrating agent.
How many moles are in P2O5?
P2O5 is the empirical formula for the polymorph of P4O10. 1 mole is equal to 1 mole P2O5, or 141.944522 grams. This conversion is based on the molar mass ratio for the two compounds. P2O5 is named diphosphorus pentaoxide.
Is P2O5 a neutral oxide?
Phosphorus pentoxide has a very high oxidation state. So the above oxide is acidic in nature. N2O is a neutral oxide. It neither reacts with acid nor base.
How do you identify a neutral oxide?
Neutral oxides show neither basic nor acidic properties and hence do not form salts when reacted with acids or bases, e.g., carbon monoxide (CO); nitrous oxide (N2O); nitric oxide (NO), etc., are neutral oxides.
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