Question

Combustion of 135.2 g of a compound produces 440.0 g CO2 and 135.0 g H2O. The molar mass of the compound is 270 g/mol. Determine the empirical and molecular formula of the hydrocarbon (show all work)

Answer 1

moles of CO2 = 440 / 44 = 10

moles of C= 10

mass of Carbon = 12 x 10 = 120 g

moles of H2O = 135 / 18 = 7.5

moles of H = 2 x 7.5 = 15

C                   H

10          15

1                    1.5

1                     3/2

2                      3

C2H3 -----------------------> empirical formula

empirical formula mass = 24 + 3 = 27 g

n = molar mass / empirical formula mass

    = 270 / 27

     = 10

molecular formula = 10 x empirical formula

                               = C20H30