Question

A 5.691 g sample of one such additive containing only lead, carbon, and hydrogen was burned in an oxygen‑rich environment. The products of the combustion were 6.194 g CO2(g) and 3.169 g H2O(g) .Determine the empirical formula of the gasoline additive.

empirical formula:[ CHPb ]

Answer 1

C %    = 12*wt of CO2*100/44*wt of organic compound

          = 12*6.194*100/44*5.691   = 29.7%

H%   = 2*wt of H2O*100/18*wt of organic compound

         = 2*3.169*100/18*5.691   = 6.18%

Pb%   = 100-(C%+ H%)

           = 100-(29.7+6.18)   = 64.12%

Element             %                         A.Wt               Relative number                    simple ratio

C                     29.7                        12                   29.7/12 = 2.475                                    2.475/0.31   = 8

H                      6.18                        1                   6.18/1    = 6.18                                        6.18/0.31     = 20

Pb                     64.12                   208                64.12/208   = 0.31                                    0.31/0.31    = 1

The empirical formula   = C8H20Pb