How decreasing order of acidic strength possible for :

H₃PO₂ > H₃PO₃ > H₃PO₄ ??

Hi mainak

if we look at the structure of those three we can easily find that basicity for

1.  H₃PO₂   is 1

2. H₃PO₃  is 2   and

3. H₃PO₄    is  3

and since basic character is increasing hence acidic character is decreasing.....for the structures go through any inorganic chemistry book

hi 

mainak

all oxoacids of phosphorous has typically two types of bonds i.e. P-H& P-OH

only P-OH is ionisable,H₃PO₂ has only one P-OH bond it will furnish all its hydrogen ions in a single step.

other are dibasic&tribasic  which do it in steps.

hence, K_a for h₃po₂  is highest &hence strongest acid.

if you like my answer ,please approve it.