The oxyacid (HPO3)n has different structures based on the value of n. If n=3,

The oxyacid H2P2O5 has the following structure.

The structures of the H4P2O6 and H4P2O7 are

Oxyacid having P−H bond can reduce AgNO3 to
Ag. Hence, H4P2O5 can create silver mirror with silver nitrate.