Final answer:
The empirical formula of a hydrocarbon is found by determining the mole ratio of carbon to hydrogen from the masses of CO2 and H2O produced in a combustion reaction. Then, the molecular formula is deduced by comparing the molar mass of the compound to the mass of the empirical formula.
Step-by-step explanation:
To determine the empirical formula of the hydrocarbon, we'll start by figuring out the molar amounts of carbon and hydrogen that were in the original sample. For carbon, each mole of CO2 contains one mole of carbon. Using the molar mass of CO2 (44.01 g/mol), we find the moles of carbon in the CO2 produced.
For hydrogen, each mole of H2O contains two moles of hydrogen. Using the molar mass of H2O (18.02 g/mol), we find the moles of hydrogen in the H2O produced.
The empirical formula is determined by the simplest whole number ratio of moles of carbon to hydrogen. Finally, to find the molecular formula, we divide the molar mass of the compound (78.11 g/mol) by the empirical formula mass. If this gives us a whole number, we multiply the subscripts in the empirical formula by this number to obtain the molecular formula.