What is the empirical formula for a sample containing 81.70% carbon and 18.29% hydrogen?

Given: C = 81.70% = 81.70g

H = 18.29% = 18.29g

The number of moles is given by: n = Given mass (m) / Molar Mass (M)

M of C = 12 g/mol

M of H = 1 g/mol

Thus, the number of moles of carbon = 81.70g / 12gmol = 6.83moles

and, the number of moles of hydrogen = 18.29/1g/mol = 18.29 moles

The ration of C moles with hydrogen:

H:C = 18.29moles/6.83moles = 2.67 ≈3

Thus, the empirical formula is C3H8