Step 1: Determine the empirical formula. Assume a 100 g sample of the hydrocarbon. Mass of Carbon (C) = 83.3 g Mass of Hydrogen (H) = 16.7 g Calculate the moles of each element: Moles of C $= \frac{83.3 \text{ g}}{12 \text{ g/mol}} = 6.9417 \text{ mol}$ Moles of H $= \frac{16.7 \text{ g}}{1 \text{ g/mol}} = 16.7 \text{ mol}$ Divide by the smallest number of moles to find the simplest mole ratio: Ratio of C $= \frac{6.9417}{6.9417} = 1$ Ratio of H $= \frac{16.7}{6.9417} \approx 2.4057$ To obtain whole numbers, multiply the ratios by a suitable integer. Since $2.4057 \approx 2.4 = \frac{12}{5}$, we multiply both ratios by 5: C: $1 \times 5 = 5$ H: $2.4057 \times 5 = 12.0285 \approx 12$ The empirical formula is $C_5 H_{12}$. Step 2: Calculate the empirical formula mass. Empirical formula mass $= (5 \times \text{atomic mass of C}) + (12 \times \text{atomic mass of H})$ Empirical formula mass $= (5 \times 12 \text{ g/mol}) + (12 \times 1 \text{ g/mol})$ Empirical formula mass $= 60 \text{ g/mol} + 12 \text{ g/mol} = 72 \text{ g/mol}$ Step 3: Determine the molar mass from the vapor density. The question states "the vapor density of the hydrocarbon is 36 gdm$^{-3}$". In chemistry problems, "vapor density" is often used to refer to the relative vapor