Which of the following name-formula combinations is wrongly matched

Options

A. Metaphosphoric acid `rarr(HPO_(3))_(n)`
B. Pyrophosphoric acid `rarrH_(4)P_(2)O_(7)`
C. Pyrophosphoric acid `rarrH_(4)P_(2)O_(5)`
D. Orthophosphoric acid `rarrH_(3)PO_(3)`

Answer

4

Explanation

`H_(3)PO_(4)` is orthophosphorous acid (phosphonic acid). Orthophosphoric acid is `H_(3)PO_(4)`. In oxoacids `P`atom is tetrahedrally surrounded by other atoms. All these acids contain one `P=O` and at least one `P-OH` bond.
The oxoacids in which `P` atom has lower oxidation number (less then+5)contains (in addition to`P=O` and `P-OH` bonds)either`P-P` (e.g, in `H_(2)P_(2)O_(6)` or `P-H` (e.g.,in `H_(3)PO_(3)`) bonds but not both.
Oxoacids having `+3` oxidation state tend to disproportionate to higher and lower oxidation states. For example ,orthophosphorous acid(or phosphorus acid)on heating disproportions to give orthophosphrous acid (or phosphoric acid)and phosphine.
`4H_(3)PO_(3)+3H_(3)PO_(4)+PH_(3)`