One of the methods of preparation of per disulphuric acid, `H_(2)S_(2)O_(8)`, involve electrolytic oxidation of `H_(2)SO_(4)` at anode `(2H_(2)SO_(4)toH_(2)S_(2)O_(8)+2H^(+)+2e^(-))` with oxygen ad hydrogen as by-products in such an electrolysis, 9.722 L of `H_(2)` and `2.35L` of `O_(2)` were generated at STP. What is the weighht of `H_(2)S_(2)O_(8)` formed?