Question

The pair in which phosphorus atoms have a formal oxidation state of $+3$ is :-

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Answer 1

In oxoacids, phosphorus is tetrahedrally surrounded by other atoms. All these acids contain atleast one P = O and one P - OH bond. The oxoacids in which phosphorus has lower oxidation state (less than +5) contain, in addition to P=O and P-OH bonds, either P-P or P-H bond are present. Here, Orthophosphorus acid$\left(H_{3}P{O}_3\right)$ and pyrophosphorus acid$\left(H_4{P}_2{O}_5\right)$ have a formal oxidation state of $+3$ on phosphorus atoms.