mercury (II) oxide

mercury (II) oxide heated yields mercury plus Oxygen
2HgO(s) → 2Hg(l) + O₂(g)
HgO is 201+16 = 217 g/mol
434 g of HgO → 402 g of Hg + 32 g of O₂

Mercury + Oxygen yields Mercury (II) Oxide
2Hg + O₂ → 2HgO
HgO is 201+16 = 217 g/mol
Hg is 201 g/mol
O is 16 g/mol
402 g of Hg + 32 g of O₂ → 434 g of HgO