Electrolysis is an important technique for extraction of metals, and each ion of the solution needs a minimum voltage to get discharged and this value is expressed in terms of discharge potential. For some metal ions the discharge potentials follow the order given below :
`Li^(+) gt K^(+) gt Ca^(2+) gt Na^(+) gt Mg^(2+) gt Al^(3+) gt Zn^(2+) gt Fe^(2+) gt Ni^(2+) gt H_(3)O^(+) gt Cu^(2+) gt Hg_(2)^(2+) gt Ag^(+) gt Au^(3+)`
For some anions the discharge potentials are in the order :
`SO_(4)^(2-) gt NO_(3)^(-) gt OH^(-) gt Br^(-) gt I^(-)`
When conc. `H_(2)SO_(4)` is electrolysed with high current using Pt electrodes, the product obtained at anode is :

Options

A. `SO_(2)`
B. `SO_(3)`
C. `O_(2)`
D. `H_(2)S_(2)O_(8)`

Answer

D