Hg + 2 H2SO4 → HgSO4 + 2 H2O + SO2
This is an oxidation-reduction (redox) reaction:
SVI + 2 e- → SIV (reduction)
Hg0 - 2 e- → HgII (oxidation)
H2SO4 is an oxidizing agent, Hg is a reducing agent.
Reactants:
Products:
- HgSO4
- H2O – Water, oxidane

- SO2 – Sulfur dioxide



- Other names: Sulfurous anhydride


, Sulphur dioxide 
, Sulfurous acid anhydride 

- Appearance: Colorless gas
; Colourless gas or compressed liquefied gas with pungent odour
; Colorless gas with a characteristic, irritating, pungent odor. [Note: A liquid below 14°F. Shipped as a liquefied compressed gas.] 
- Other names: Sulfurous anhydride