Question

stronger acid determination: HSO4 − or HSeO4–  

here, O4- is same so we look at S& Se since S is more e- negative HSO4 is stronger acid

but i was wondering IF lets say (w/e if this exist or not does not matter here)

HSO4- vs HSeO5-

then what happen? S is more e- negative then Se but Se has O5- now, which is more oxoacid structure.

which is stronger now?

Answer 1

For telling you this answer let me tell you the comparison of acidic nature of H2SO4 and H2SO5 . here H2SO4 is more acidic than H2SO5

as conjugate base of H2SO4 is more stable as compare to conjugate base of H2SO5 (as HSO5- is less stable due to repulsion between lone pairs of O-O.

Similarly if we compare HSO4- and HSeO5- ,

HSO4- is more acidic due to two reasons,

1) HSeO5- is less stable due to lone pair lone pair repulsion between O nad O of peroxy bond and

2) resonance stablization in HSO4- is more effective as compare to HSeO5- as earlier has 2pπ-3dπ(more strong) bonding and later has 2pπ-4dπ( less strong).

I hope it helps.