Which of the following oxoacids of phosphorus is a reducing agent and a monobasic acid as well?

• A. H₄P₂O₅
• B. HPO₃
• C. H₃PO₃
• D. H₃PO₂

To determine which oxoacid of phosphorus is both a reducing agent and a monobasic acid, let's analyze the options provided.

Understanding the Options

• H₄P₂O₅: This is diphosphoric acid, which is not typically classified as a monobasic acid.
• HPO₃: Known as metaphosphoric acid, it is not a reducing agent.
• H₃PO₃: This is phosphorous acid, which can act as a reducing agent but is dibasic.
• H₃PO₂: Also known as hypophosphorous acid, it is a monobasic acid and a reducing agent.

Conclusion

The correct answer is H₃PO₂. It is a monobasic acid and functions as a reducing agent.