Complete combustion of 5.80 g of a hydrocarbon produced 18.6 g of CO2 and 6.36 g of H2O. What is the empirical formula for the hydrocarbon?

We need to first figure out how many carbons and hydrogen are from the products since they came from the hydrocarbon.

18.6 g (1 mol CO2 / 44 grams) (1 mol C / 1 mol CO2) = 0.423 moles C

6.36 g (1 mol H2O / 18.02 grams) (2 mol H / 1 mole H2O) = 0.706 mol H

Divide the both values by the smallest and multiple by any number until you get the smallest whole number

Carbon - 0.423/0.423 = 1 x 3 = 3

Hydrogen - 0.706 / 0.423 = 1.7 x 3 = 5

The formula is C3H5