Question

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?

Answer 1

Answer:

C8H12F6

Explanation:

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:

C8H12F6