Question

Find the oxidation number of S in H2S2O8

Answer 1

It would have been plus seven if possible, however the maximum is the number of valence electron of sulfur to be donated, so that is clearly +6 (six).
i.e. 2 +2x -16=0
=>x =7, but for sulphur x cannot be greater than 6... so this means , there is a peroxy linkage in the given compound...
and we know that ,  peroxy oxygen have oxdn. no. -1
whenever there is peroxy linkage , sulphur is always in its highest oxdn. state i.e. +6
so here, oxdn. state of sulphur is +6
now u can also find the no. of peroxy linkages..
i.e.  2+2(6) +n(-1) -(n-8)(-2) = 0
so , here n = 2.  so we have two peroxy oxygens and one peroxy linkage.

Answer 2

 To find the oxidation number first you should know about oxidation number.

Oxidation number, also called Oxidation State, the total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom.

In Peroxydisulphiric acid (H2S2O8) has sulphur in the +6 oxidation state, hydrogen in the +1 oxidation state, the two O's between the two S-atoms are in the -1 oxidation state and all other oxygens are in the -2 oxidation state.

Whenever there is peroxy linkage , sulphur is always in its highest oxdidation. state i.e. +6

so here, oxidation. state of sulphur is +6 

Answer 3

Peroxydisulfuric (H₂S₂O₈) acid is the inorganic compound. Also called Marshall's acid, it is sulfur oxoacid. It has sulfur in its +6 oxidation state and a peroxide group.