we first have to find the empirical formula.
assuming that we have 100 g of sample, the percentages convert to grams. So, we have 85.6 grams of C and 14.4 grams of H. now we need to convert the grams to moles using the molar mass of the atoms.
85.6 g C (1 mol C/ 12.0 g)= 7.13 mol C
14.4 g H (1 mol H/ 1.01 g)= 14.3 mol H
now we divide both values by the smallest to find the ratios.
Carbon---> 7.13 / 7.13= 1
Hydrogen---> 14.3 / 7.13= 2
the empirical formula= CH₂
molar mass of CH₂= 12.0 + (2 x 1.01)= 14.02 g/mol
now we have to determine the molar mass of the compound using the following formula.
molar mass= (density x gas constant x temperature) / pressure
molar mass= ( 0.549 x 0.0821 x 425 ) / 0.455 = 42.1 g/mol
let's find the ratio between this molar mass and the empirical formula molar mass.
42.1 / 14.02 = 3
so the molecular formula---> 3 x CH₂ ----> C₃H₆
