What is the empirical formula of a compound composed of 3.25% hydrogen ( H ), 19.36% carbon ( C ), and 77.39% oxygen ( O ) by mass?

Answer 1

We will convert each element to moles and then get the simplest whole number for each element.

If we assume 100 g of unknown, then the % simply becomes grams.

3.25 g H x 1 mol H / 1 g = 3.25 moles H

19.36 g C x 1 mol C / 12 g = 1.61 moles C

77.39 g O x 1 mol O / 16 g = 4.84 moles O

Dividing all values by 1.61 in an attempt to get whole numbers, we end up with...

3.25 / 1.61 = 2.0 moles H

1.61 / 1.61 = 1.0 moles C

4.84 / 1.61 = 3.0 moles O

Empirical formula = CH₂O₃