Answer
$C_{8}H_{8}O_{3}$
Work Step by Step
Assume 100g of the compound. Convert the mass of each constituent element into moles by dividing by its molar mass:
$63.15g\ C\times\frac{1mol}{12.01g}=5.258mol\ C$
$5.30g\ H\times\frac{1mol}{1.01g}=5.25mol\ H$
$31.55g\ O\times\frac{1mol}{16.00g}=1.972mol\ O$
Formulas have whole number subscripts so divide all the amounts by the smallest and round if the number is really close.
$\frac{5.258mol\ C}{1.972}=2.667\times3=8$
$\frac{5.25mol\ H}{1.972}=2.667\times3=8$
$\frac{1.972mol\ O}{1.972}=1\times3=3$
So the empirical formula for this compound is:
$C_{8}H_{8}O_{3}$
