Question

Isobutylene is a hydrocarbon used in the manufacture of synthetic rubber. when 0.847 g of isobutylene was subjected to combustion analysis, the gain in mass of the co2 absorber was 2.657 g and that of the h2o absorber was 1.089 g. what is the empirical formula of isobutylene?

Answer 1

Find the mass of C in the 2.657 g CO2:
(2.657 g CO2) / (44.01 g/mol) = 0.06037 mol CO2
Since each mole of CO2 also has 1 mole of C, this is equivalent to 0.06037 mol C.

Find the mass of H in the 1.089 g H2O:
(1.089 g H2O) / (18.02 g/mol) = 0.06043 mol H2O
Since 1 mol H2O has 2 mol H, this is equivalent to (0.06043)*2 = 0.1209 mol H.

Taking the ratio of H to C: 0.1209 / 0.06037 = 2.002 ~ 2
Therefore, the empirical formula of isobutylene is CH2.