Which of the following statements is not valid for oxoacids of phosphorus?

Which of the following statements is not valid for oxoacids of phosphorus?
  1. Orthophosphoric acid is used in the manufacture of triple superphosphate
  2. Hypophosphorous acid is a diprotic acid
  3. All oxoacids contain tetrahedral four coordinated phosphorus
  4. All oxoacids contain at least one $\mathrm{P}=\mathrm{O}$ unit and one $\mathrm{P}-\mathrm{OH}$ group

Solution

Hypophosphorous acid, $\mathrm{H}_3 \mathrm{PO}_2$, has the following structure. As it contains only one replaceable $H$-atom (that is attached with $\mathrm{O}$, not with P directly) so it is a monoprotic acid. All other given statements are true.

Asked in: NEET 2012 (Screening)

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