Question

The formula of meta phosphoric acid is :
(A)${{H}_{2}}P{{O}_{3}}$
(B)${{H}_{3}}P{{O}_{3}}$
(C)$HP{{O}_{3}}$
(D)${{H}_{4}}{{P}_{2}}{{O}_{7}}$

Answer 1

Hint: Acid with oxidation number +5 ends with -ic suffix. And acid with oxidation number +3 ends with –ous suffix. Meta phosphoric acid is a very weak acid.Phosphorous form various oxoacids.These acids are generally seen too disproportionate to either lower and higher oxidation states.

Complete step by step answer: The formula of meta phosphoric acid is $HP{{O}_{3}}$. Meta phosphoric acid is a corrosive, inorganic, cyclic polyphosphate formed from bonded phosphoric units. It has a molar mass of 80g/mol.It has applications in biochemistry, agriculture, pharmacy and chemical research.
-Considering other options, Option (A), ${{H}_{2}}P{{O}_{3}}$, it is Dihydrogen phosphite. Dihydrogen phosphite is a monovalent inorganic anion obtained by deprotonation of phosphoric acid. It is a conjugate base of a phosphorous acid. It is a conjugate acid of a hydrogen phosphite.
-Considering option (B), ${{H}_{3}}P{{O}_{3}}$, it is phosphorus acid. This acid is diprotic acid. It has a molar mass of 82g/mol.
-Considering option (D), ${{H}_{4}}{{P}_{2}}{{O}_{7}}$, it is pyrophosphoric acid. It is also known as Diphosphoric acid. IT is colorless, odourless. It is soluble in water, diethyl ether, and ethyl alcohol. It has a molar mass of 177.98g/mol.

Note: $HP{{O}_{3}}$ is a very weak acid. Phosphorus acid has pka in the range of 1.26-1.3. The Hydrogen atom bonded directly to the phosphorus atom is not readily ionizable. On heating at ${{200}^{\circ }}$C, phosphorus acid disproportionate to phosphoric acid and phosphine.