Empirical formula

Question

Complete combustion of 2.50 g of a hydrocarbon produced 8.04 g of CO₂ and 2.74 g of H₂O. What is the empirical formula for

the hydrocarbon? Insert subscripts as necessary.

Answer 1

moles of C = 8.04 g CO2 x 1 mol CO2 / 44 g x 1 mol C / mol CO2 = 0.1827 mols C

moles H = 2.74 g H2O x 1 mol H2O / 18 g x 2 mol H / mol H2O = 0.3044 mols H

Divide by 0.1827 to try to get whole numbers of moles

C = 0.1827 / 0.1827 = 1 mol C

H = 0.3044 / 0.1827 = 1.668

Multiply by 3 to get whole numbers of moles

C = 1 x 3 = 3 mols C

H = 1.668 x 3 = 5 mols H

Empirical formula = C₃H₅