Formula of Caro's acid is

All oxo acids of Sulphur are dibasic ;In all oxo acids, Sulphur atom is sp3 hybridized ;All the pi bonds are dπ-pπ bonds;Sulphur atom having 2 sigma bonds, 1 double bond and a lone pair around it has pyramidal arrangement around it ;Sulphur atom having 2 sigma bonds, 1 double bond and a lone pair around will be tetravalent with +4 O.S (or) +3 O.S;Sulphur atom having 2 sigma bonds, 2 double bond and no lone pairs around it has tetrahedral arrangement around it ;Sulphur atom having 2 sigma bonds, 2 double bond and no lone pair around will be hexavalent with +6 O.S (or) +5 O.S;Note : Do not forget to count a sigma bond between Oxygen and Hydrogen in O-H bond ;