sulphuric acid is very much widley used in chemical reactions as an strong acid, but it is also used an strong oxidizer. Sulphuric acid demosntrates high magnitude of oxidizing potential. This due to the sulphur present in the molecule. In sulphuric or in sulphate, the oxidation number of sulphur is +6, which is the hoghest sulphur can achieve. Therefore it can oxidize other materials while reducing its oxidation state.
There are a lot of well known redox reactions where sulphuric acid is involved. One such reaction is,
C + 2 H2SO4 → CO2 + 2 SO2 + 2 H2O
Here Carbon is oxidized into CO2 (Its oxidation number changes from 0 to +4) while H2SO4 is converted to SO2 (Its oxidation number reduces from +6 to +4)
Similarly, it reacts with elemental sulphur also.
S + 2 H2SO4 → 3 SO2 + 2 H2O
Example redox reaction:
Reacton with halide ions (Br-)
2Br- ------> Br2 + 2e
H2SO4 + 2H+ + 2e ------> SO2 + 2H2O