compound consists of 85.6% carbon and 14.4% hydrogen. The molar mass of the compound is 84.2 g/mol. Find the empirical and molecular formulas of the compound

Answer 1

To find the empirical formula, we want to find the number of moles of (whole numbers) of each element.

Assume 100 g of unknown;

For C: 85.6 g C x 1 mol C / 12 g = 7.13 mols C

For H: 14.4 g H x 1 mol H / 1 g = 14.4 mols H

Divide both by 7.13 to get whole numbers...

C = 7.13 mols / 7.13 = 1 mol C

H = 14.4 mols / 7.13 = 2 mol H

Empirical formula = CH₂

To find the molecular formula, we find how many of the empirical formula fit into the molar mass of the molecular formula. Molar mass CH₂ = 14

84.2 / 14 = 6

Molecular formula = 6 x the empirical formula = C₆H₁₂