Question

The pair that contains two $P-H$ bonds in each of the oxoacids is:
A. $H_{3}^{{}}PO_{2}^{{}}\text{ and }H_{4}^{{}}P_{2}^{{}}O_{5}^{{}}$
B. $H_{4}^{{}}P_{2}^{{}}O_{5}^{{}}\text{ and }H_{4}^{{}}P_{2}^{{}}O_{6}^{{}}$
C. $H_{3}^{{}}PO_{3\text{ }}^{{}}and\text{ }H_{3}^{{}}PO_{2}^{{}}$
D. $H_{4}^{{}}P_{2}^{{}}O_{5}^{{}}\text{ and H}_{3}^{{}}PO_{3}^{{}}$

Answer 1

Hint: Before solving this question, we should know what oxoacids are. As the name suggests, Oxoacids are the acids that contain Oxygen. And what are oxoacids of phosphorus Mostly, all the oxoacids of phosphorus have one $P-OH$ bond and one $P=O$ bond. They have different oxidation states.

Complete step-by-step answer:
Oxoacids are acids that have an Oxygen element. Phosphorus forms various oxoacids like $H_{3}^{{}}PO_{4}^{{}},\,H_{3}^{{}}PO_{3}^{{}}$ etc. They are surrounded by many different atoms. $P-P\,\,or\,P-H$ can be seen too with $P=O$ bonds and $P-OH$ bonds in the compounds of oxoacids of phosphorus. In these compounds, the oxidation state of the Phosphorus element is never greater than +5.
$H_{3}^{{}}PO_{2}^{{}}$(Hypophosphorous acid) – As we can see with the help of the structure, It has two $P-H$ bonds.
It is the acid that is monobasic and weak. Their acidic characteristics are shown by releasing a singular H- atom.

$H_{3}^{{}}PO_{3}^{{}}$(Phosphorous acid) –As we can see with the help of the structure, It doesn’t have two $P-H$ bonds.
Its formula suggests the phosphoric acid to be triprotic but it is diprotic.

$H_{4}^{{}}P_{2}^{{}}O_{5}^{{}}$(Pyrophosphorous acid) – As we can see with the help of the structure, It has two $P-H$ bonds. It is also called diphosphorus acid.

$H_{4}^{{}}P_{2}^{{}}O_{6}^{{}}$(Hypophosphoric acid) – As we can see with the help of the structure, It doesn’t have two $P-H$ bonds. It is also known as mineral acid. It has an oxidation state of +4.

Hence, the correct answer is Option (A) $H_{3}^{{}}PO_{2}^{{}}\text{ and }H_{4}^{{}}P_{2}^{{}}O_{5}^{{}}$.

Note: Oxoacids of phosphorus are surrounded by four other atoms but in the case of ${{H}_{3}}P{{O}_{3}}$, it is dibasic due to the presence of two $P-OH$ bonds. The $P-H$ bonds that are there in the oxoacids don’t get ionized to give $H_{_{{}}}^{+}$ ions but the H atoms that are attached with Oxygen, are readily ionizable.