Question

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?

A) 16.0 g/mol

B) 30.1 g/mol

C) 44.1 g/mol

D) 72.2 g/mol

E)   92.1 g/mol

Answer 1

1)

Determine the grams of carbon in 3.5927 g CO₂ and the grams of hydrogen in 1.9584 g H₂O.

carbon: 3.59270 g x (12.011 g / 44.0098 g) = 0.98 g

hydrogen: 1.9584 g x (2.0158 g / 18.0152 g) = 0.2191 g

2) Convert grams of C and H to their respective amount of moles.

carbon: 0.98 g / 12.011 g/mol = 0.08159 mol

hydrogen: 0.2191 g / 1.0079 g/mol = 0.2173 mol

3) Divide each molar amount by 0.0272, , seeking to modify the above molar amounts into small, whole numbers.

carbon: 0.08159 mol / 0.0272 mol = 3

hydrogen: 0.2173 mol / 0.0272 mol = 8

We have now arrived at the answer: the empirical formula of the substance is C3H8

molar mass = 44.1 g/mol

so, answer is 44.1