A gas is 85.7% carbon and 14.3% hydrogen by mass, and 1.56 g of it fills 1.00 L at 0.984 atm and 50 degrees C. What is its molecular formula?

1. Take 100 g of the gas, giving 85.7 g of carbon and 14.3 g of hydrogen. 2. Convert to moles: 85.7 / 12.01 = 7.136 mol C and 14.3 / 1.01 = 14.158 mol H. 3. Divide both by the smaller value: 1.00 mol C to 1.98 mol H, so the empirical formula is CH2 with an empirical mass of 14.03 g. 4. Now find the molar mass from the density data using M = density x R x T / P. 5. Convert the temperature to kelvin: 50 + 273 = 323 K. 6. Compute: 1.56 g/L x 0.0821 L atm/mol K x 323 K = 41.37, then divide by 0.984 atm to get 42.0 g/mol. 7. Divide molar mass by empirical mass: 42.0 / 14.03 = 2.99, which rounds to 3. 8. Three CH2 units give C3H6, so stopping at the empirical formula CH2 is the trap this question sets. _Source: OpenStax Chemistry (CC BY 4.0), Ch 9 "Gases", section 9.3 Stoichiometry of Gaseous Substances, Mixtures, and Reactions_