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Tuesday, May 4, 2021

Prefix “Hypo-acids”, and “Per-acids”:

 The prefix “Hypo” use for those oxy acid having lower oxidation state than either “us” or “ic” oxy acid for example Hypophosphorous acid (H3PO2), Hypophosphoric acid (H4P2O6)  and hyposulphurous acid (H2S2O4). For exitence of hypo acid  for an oxy acid, it must be a parent oxy acid contains at least two hydrogen atoms except nitrous acid (HNO2).

Example; Which of the following parent acid does/do not has correspong “Hypo” oxy acid?

(A) HNO3 (B) H3PO4 (C) H2SO4 (4) HClO4

Answer Key : A and D

The prefix “per” used to an oxy acid  which is obtained by adding one oxygen atom to the a respective “ic oxy acids” for example sulphuric acid (H2SO4) and its per sulphuric acid/caro’s acid is (H2SO5) which is contains one (-O-O-) peroxy linkage. And also hydrochloric acid (HClO4) and Perhydrochloric acid (HClO5).

Per-acid having two central atoms is formed by adding one oxygen atom to its pyro-ic-acid. For pyrosulphuric acid (H2S2O7) and pyrophosphoric acid (H4P2O7) and their per-oxy-acids are perdisulphuric acid/marshal’s acid (H2S2O8) and perdiphosphoric acid (H4P2O8) repectivily.

Conclusion: If –OH group attach to that central atom having lone pair and vacant orbitals and tendency to expand its orbitals then there is possibility of tautomerised. If size of central atom is should be small then there will be no tautomerism, so in case of Antomony,Arsenic while drawing structure of oxy acids all the hydrogen atoms are converted into –OH groups and they are symmetrical bonded to all central atoms. How ever this rule is not applicable for those oxy acidsof phosphorous in which oxidation state of phosphorous is +1 or +3.

Basicity of an oxy acid is equal to number of –OH groups presents in it exceptin oxy acid of boron. Oxy acid of boron does not furnish H+ rather it act as Lewis acid.

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