Apure sample of a hydrocarbon was analyzed and found to contain 12.00 g of carbon and 1.5 g of hydrogen.
a. find the empirical formula of the compound. (hint: as the masses are known, you do not need to assume you have a 100 g sample).
b. if the molar mass of the hydrocarbon is found to be 54.10 g/mol, what is its molecular formula?

Explanation:

First question: a. Find the empirical formula of the compound

1) Calculate the number of moles of every element that is in the hydrocarbon

2) Divide by the least number of moles, to find the mol ratio:

3) Multiply by 2 to obtain whole numbers:

Thus, the mole ratio is 2 : 3, and the empirical formula is C₂ H₃

Second question: b. What is the molecular formula?

1) Find the mass of the empirical formula:

Molar mass of the empirical formula = 24.02  g/mol + 3.024 g/mol = 27.044 g/mol ≈ 27.04 g/mol

2) Find the number of times that the empirical mass is contained in the molar mass:

3) Multiply every atom in the empirical formula by the ratio 2: