A hydrocarbon contains C,H, and F atoms. A 5.43 g sample of this hydrocarbon was analyzed and the mass of 2.35 g of carbon and 0.294 g of hydrogen. The molar mass of this compound was measured between 219-225 g/mol, what is the molecular formula of the hydrocarbon that contains C,H and F?

To solve this question we need to find the moles of each atom in order to find the empirical formula (The empirical formula is defined as the simplest whole-number ratio of atoms present in a molecule). Using the empirical formula and the molar mass we can find molecular formula as follows:

Moles C:

2.35g * (1mol / 12g) = 0.1958 moles C

Moles H:

0.294g (1mol /1g) = 0.294 moles H

Moles F -Molar mass: 19.0g/mol-:

Mass F: 5.43g - 2.35g C - 0.294g H = 2.786g F * (1mol / 19.0g) = 0.1466 moles F

The moles of atoms dividing in the moles of F (Lower number of moles) produce the simplest ratio as follows:

C = 0.1958mol C / 0.1466mol F = 1.33

H =0.294mol H / 0.1466mol F = 2

F = 0.1466 mol F / 0.1466mol F = 1

As the empirical formula requires whole numbers, this ratio multiplied 3 times:

C = 4

H = 6

F=3

The empirical formula is:

C4H6F3

With molar mass of:

4C = 12*4 = 48

6H = 1*6 = 6

3F = 19*3 = 57

The molar mass is: 48g/mol + 6g/mol + 57g/mol = 111g/mol

As we know the molecule has a molar mass between 219-225g/mol and the empirical formula is 111g/mol, 2 times empirical formula will produce a molecule with the molar mass of the molecule, that is: