The combustion of 0.0272 mole of a hydrocarbon produces 1.9584 g H2O and 3.5927 g CO2. What is the molar mass of the hydrocarbon?

Assuming that the hydrocarbon only contains hydrogen and carbon, then it will have the formula CxHy where x and y represents the number of carbon and hydrogen atoms, respectively. We proceed as follows:

CxHy + ((x+y/2) / 2) O2 = xCO2 + y/2H2O

1.9584 g H2O (1 mol / 18.02 g) (2 mol H / 1 mol H2O) = 0.0272y

y = 8 mol H

3.5927 g CO2 (1 mol / 44.01 g) (1 mol C / 1 mol CO2) = 0.0272x

x = 3 mol C

C3H8 = 44.11 g / mol