Question

Draw the structure of:
A.Pyrophosphoric acid
B.Pyro phosphorous acid
C.Poly metaphosphoric acid
D.Cyclo trimetaphosphoric acid

Answer 1

To answer this question, you should recall the concept of oxoacids of phosphorus. Phosphorus belongs to group 15 of the periodic table and forms various oxoacids: hypo phosphorous acid$\left( {{H_3}P{O_2}} \right)$, Phosphorous acid$\left( {{H_3}P{O_3}} \right)$, Hypo phosphoric acid$\left( {{H_3}P{O_4}} \right)$, pyro phosphoric acid $\left( {{H_4}{P_2}{O_7}} \right)$and poly metaphosphoric acid${\left( {HP{O_3}} \right)_n}$.

Complete Step by step solution:
Oxoacids of phosphorus which contain phosphorus-oxygen linkages are the most dominated subset in Phosphorus Chemistry.
Pyro phosphoric acid is a tetrabasic acid and prepared by heating orthophosphoric acid at about ${250^o}{\text{C}}$ : $2{H_3}P{O_4} \to {H_4}{P_2}{O_7} + {H_2}O$ The structure of Pyro phosphoric acid can be represented as:

The chemical formula of pyrophosphoric acid is ${H_4}{P_2}{O_5}$. The structure can be represented as:

The formula for Poly metaphosphoric acid is ${(HP{O_3})_n}$. It has a linear polymer structure where the oxidation state of phosphorus is +5. The structure can be represented as:

Cyclo trimetaphosphoric acid is a tribasic acid of phosphorus which has a formula ${(HP{O_3})_3}$. The three metaphosphoric acid molecules form a ring structure. Phosphorus is in the $+ 5$ oxidation state. In this structure, there are three $P - OH$ bonds, three $P = O$ bonds, and three $P - O - P$ bonds:

Note: Important acidic nature of oxoacids of phosphorus: You are already aware of the term acids. These acids show varied physical and chemical properties of acids. Some simple ones are – they need a pH below 7, they turn blue paper red, they need a sour taste and that they react with alkalis to make salts. There is little difference of acidic strength among ${{\text{H}}_{\text{3}}}{\text{P}}{{\text{O}}_{\text{4}}}{\text{, }}{{\text{H}}_{\text{3}}}{\text{P}}{{\text{O}}_{{\text{3}}}}{\text{ and }}{{\text{H}}_{\text{3}}}{\text{P}}{{\text{O}}_{\text{2}}}$ because the hydrogen in these acids aren't all bonded to oxygen, and phosphorus isn't a highly electronegative element i.e. its oxides are less basic and electronegativities of ${\text{P}}$ and ${\text{H}}$ are almost the same. Hence, they all have almost similar acidic strength.