Oxoacids of phosphorous having strong reducing properties

Hypophosphorous acid & Phosphoric acid

The correct answer is Option (2) → Hypophosphorous acid & Phosphoric acid.

The oxoacids of phosphorus exhibit different chemical properties, including their ability to act as reducing agents. The strength of reducing properties is generally linked to the number of hydrogen atoms bonded directly to phosphorus, which can be oxidized during a reaction.

Explanation of Oxoacids of Phosphorus:

Phosphoric Acid (H₃PO₄): This acid has no hydrogen atoms directly bonded to phosphorus. As a result, it does not exhibit strong reducing properties.

Orthophosphoric Acid (H₃PO₄): This is another name for phosphoric acid and similarly lacks reducing properties.

Hypophosphorous Acid (H₃PO₂): This acid has one -OH group and two hydrogens directly bonded to phosphorus. Due to the presence of these P-H bonds, it acts as a strong reducing agent.

Cyclotrimetaphosphoric Acid (H₃P₃O₉): This cyclic form of phosphoric acid also lacks P-H bonds and therefore does not exhibit reducing properties.

Pyrophosphoric Acid (H₄P₂O₇): This acid is formed by the condensation of two molecules of orthophosphoric acid, and it does not have P-H bonds, making it a poor reducing agent.

Conclusion:
The oxoacid that has strong reducing properties is Hypophosphorous Acid (H₃PO₂), due to the presence of P-H bonds. Phosphoric acid (H₃PO₄) and its derivatives do not show strong reducing properties.

Thus, the correct answer is: Hypophosphorous Acid & Phosphoric Acid.