Final answer:
To find the empirical formula of the hydrocarbon, the masses of carbon and hydrogen are first converted to moles, then ratios of these moles are calculated to determine the simplest whole number ratio, resulting in an empirical formula of C3H8.
Step-by-step explanation:
To find the empirical formula of a hydrocarbon with 81.7 g of carbon (C) and 18.3 g of hydrogen (H), we first convert these masses into moles. For carbon, we have 81.7 g C ÷ 12.01 g/mol C = 6.804 mol C. For hydrogen, 18.3 g H ÷ 1.01 g/mol H = 18.119 mol H. Next, we divide the moles of each element by the smallest number of moles obtained to get the simplest ratio of atoms. In this case, we divide both by 6.804 mol to get:
- C: 6.804 mol C ÷ 6.804 mol = 1
- H: 18.119 mol H ÷ 6.804 mol = approximately 2.66, which is close to 8/3
Thus, when we multiply both numbers by 3 to convert the ratio into whole numbers, the empirical formula is C3H8.