Question

How many $P-O-P$ linkage(s) is/are present in tetra polyphosphoric acid?

Answer 1

There are four molecules of phosphoric acid in tetra polyphosphoric acid. There are a total of 3 oxygen linkages between the molecules in tetra polyphosphoric acid.

Complete step by step answer:
Tetra Polyphosphoric acid is a compound that is an oxoacid of phosphorus which belongs to group 15 of the p-block.
There are four molecules of phosphoric acid joined together to form tetra polyphosphoric whose formula is ${{H}_{6}}{{O}_{13}}{{P}_{4}}$. The other names of tetra polyphosphoric acid are Hydroxy Phosphono phosphate and phosphono hydrogen phosphate.
The molecular weight or mass of Tetra Polyphosphoric is $337.94\text{ g/mol}$.
The structure of Tetra Polyphosphoric is given below:

So, from the structure we can see that there are 3 oxygen linkages between the phosphorus molecules, each phosphorus is linked to an oxygen atom by a double bond. The terminal phosphorus molecules have two $OH$ bonds each and both the middle phosphorus have one $OH$ bond.

So, there are three $P-O-P$ linkages present in tetra polyphosphoric acid.

Additional information:
Other oxoacids of phosphorus having $P-O-P$ linkage(s) are given below:
Pyrophosphoric acid whose formula is ${{H}_{4}}{{P}_{2}}{{O}_{7}}$ and is made up of two molecules of phosphoric acid. There is one $P-O-P$ linkage in pyrophosphoric acid. The structure is given below:

Cyclotrimetaphosphoric acid whose formula is ${{(HO{{P}_{3}})}_{3}}$ and is made up of three molecules of phosphoric acid. It has a cyclic structure and there are three $P-O-P$ linkages present between the phosphorus molecules. The structure is given below:

Note: The oxidation state of phosphorus in tetra polyphosphoric acid is +5. The oxidation state of phosphorus in Pyrophosphoric acid is +5 and in Cyclotrimetaphosphoric acid, the oxidation state of phosphorus is also +5. All these molecules are neutral.