Burning 0.00126 g of polyethylene gives 0.00394 g CO2 (44.01 g/mol) and 0.00161 g H2O (18.02 g/mol). What is its empirical formula?

1. Assume every carbon atom ends up in CO2 and every hydrogen atom in H2O. 2. Moles of CO2 equal 0.00394 divided by 44.01, which is 8.95 times ten to the minus five mol. 3. Each CO2 carries one carbon atom, so moles of C equal 8.95 times ten to the minus five. 4. Moles of H2O equal 0.00161 divided by 18.02, which is 8.93 times ten to the minus five mol. 5. Each H2O carries two hydrogen atoms, so moles of H equal 1.79 times ten to the minus four. 6. The H to C ratio is 1.79 times ten to the minus four over 8.95 times ten to the minus five, that is 2 to 1. 7. So the empirical formula is CH2, and forgetting to double the hydrogen would wrongly give CH. _Source: OpenStax Chemistry (CC BY 4.0), Ch 4 "Stoichiometry of Chemical Reactions", section 4.5 Quantitative Chemical Analysis_