Find the total number of diprotic acids among the following:
`H_(3)PO_(4), H_(2)SO_(4), H_(3)PO_(3), H_(2)CO_(3), H_(2)S_(2)O_(7), H_(3)BO_(3), H_(3)PO_(2), H_(2)CrO_(4), H_(2)SO_(3)`

Explanation

Diprotic acids are those which furnish two protons per molecule.
`H_(2)SO_(4), H_(3)PO_(3), H_(2)CO_(3), H_(2)S_(2)O_(7), H_(3)CrO_(4), H_(2)SO_(3)`
`H_(3)BO_(3) +H_(2)O rarr B(OH)_(4)^(Theta) +H^(o+)` (Monobasic)
`H-O-underset((H_(2)S_(2)O_(7)))(overset(O)overset(||)underset(O)underset(||)(O)-O)-overset(O)overset(||)underset(O)underset(||)(S)-O-H("Diabasic")`
Only those hydrogensa re replaceable form oxy-acids of phoshorous and sulphur which are attached to oxygen.
`H_(3)PO_(4)` (Tribasic)
`H_(3)PO_(3)` (Dibasic)
`H_(3)PO_(2)` (Monobasic)