How do you find the empirical formula?

Question

There are 2 binary compounds of mercury and oxygen. Heating either of them results in the decomposition of the

compound, with oxygen gas escaping into the atmosphere while leaving a residue of pure mercury. Heating 0.6498 g

of one of the compounds leaves a residue on 0.6018 g. Heating 0.4172 g of the other compound results in a mass

loss of 0.016 g. Determine the empirical formula of each compound.

Answer 1

first compound

0.6498 g total - 0.6018 g Hg = 0.048 grams of oxygen

find moles:

0.6018 g Hg  @ 200.59 g/mol = 0.003 moles Hg

0.048 g O @ 16 g.mol = 0.003 moles O

that's a 1:1 ratio of moles

first empirical formul answer is HgO

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next

0.4172 g total - 0.016 grams of oxyjen lost = 0.4156 grams of Hg

find moles:

0.016 g O @ 16 g/mol - 0.001 moles O

0.4156 g Hg @ 200.59 g/mol = 0.002 moles of Hg

that's a 2 :1 ratio of moles

Your last empirical formula : Hg2O