The most common, orthophosphoric acid, H3PO4, is usually simply called phosphoric acid. Two molecules of it are formed by adding three molecules of water, H2O, to one molecule of phosphorus pentoxide (phosphoric anhydride, P2O5).


P2​O5​+3H2​O⟶2H3​PO4​

**Conversion of P2O5 to Orthophosphoric Acid**

**Introduction:**
P2O5 is a chemical formula for diphosphorus pentoxide, which is an anhydride of phosphoric acid. Orthophosphoric acid, also known as phosphoric acid (H3PO4), is a weak acid commonly used in various industries. To convert 1 molecule of P2O5 to orthophosphoric acid, a specific number of water (H2O) molecules are required. This process involves the hydration of P2O5.

**The Equation:**
The balanced chemical equation for the conversion of P2O5 to orthophosphoric acid is:

P2O5 + 3H2O → 2H3PO4

This equation shows that 1 molecule of P2O5 reacts with 3 molecules of water to produce 2 molecules of orthophosphoric acid.

**Explanation:**
To understand the number of water molecules required for the conversion, we need to analyze the stoichiometry of the balanced equation.

- According to the equation, 1 molecule of P2O5 reacts with 3 molecules of H2O.
- This means that for every 2 molecules of H3PO4 produced, 3 molecules of H2O are consumed.
- Therefore, the ratio of H2O to P2O5 is 3:1.

**Mole-to-Mole Ratio:**
Using the mole-to-mole ratio, we can determine the number of water molecules required to convert 1 molecule of P2O5 to orthophosphoric acid.

- The molar mass of P2O5 is approximately 141.95 g/mol.
- The molar mass of H2O is approximately 18.02 g/mol.

By comparing the molar masses, we can deduce the ratio of moles:

- P2O5: 1 mole
- H2O: 3 moles

**Avogadro's Number:**
To convert moles to molecules, we need to use Avogadro's number, which is approximately 6.022 x 10^23 molecules/mol.

- P2O5: 6.022 x 10^23 molecules
- H2O: 3 x (6.022 x 10^23) molecules

Therefore, to convert 1 molecule of P2O5 to orthophosphoric acid, we require 3 x (6.022 x 10^23) molecules of H2O.

**Conclusion:**
In conclusion, the number of water molecules required to convert 1 molecule of P2O5 to orthophosphoric acid is 3 x (6.022 x 10^23). This calculation is based on the balanced chemical equation and the stoichiometry of the reaction.