Write chemical equation for the following reaction: Cinnabar is heated in the presence of air.

Cinnabar is heated in the presence of air: HgS(Cinnabar) + O2(Air) → SO2 + HgO
HgO → Hg + O2
When cinnabar (an ore of mercury) is heated in air, it is first converted into mercuric oxide (HgO), which is then reduced to mercury on further heating.