The molar mass of hgo is 216.59 g/mol. the molar mass of o2 is 32.00 g/mol. how many moles of hgo are needed to produce 250.0 g of o2?

A reaction in which Oxygen (O₂) is produced from Mercury Oxide (HgO) would be a decomposition reaction.
           2HgO    →    2Hg    +    O₂

If 250g of O₂ is needed to be produced,
then the moles of oxygen needed to be produced = 250g  ÷  32 g/mol
                                                                                     = 7.8125 mol

Now, the mole ratio of Oxygen to Mercury Oxide is  1  :  2
∴ if the moles of oxygen =  7.8125 mol
then the moles of mercury oxide = 7.8125 mol × 2
                                                        = 15.625 mol

Thus the number moles of HgO needed to produce 250.0 g of O₂ is 15.625 mol
 

The answer is 323 g.