Question

Tetrahydrocannabinol (thc) is composed of 80.24% carbon, 9.62% hydrogen and 10.14% oxygen by mass. what is the empirical formula of thc?

Answer 1

80.24% carbon, 9.62% hydrogen and 10.14% oxygen

1) Base: 100 g

C: 80.24 g
H: 9.62 g
O: 10.14 g
      ----------
      100.00 g

2) Conversion to moles

C: 80.24 g / 12.00 g /mol = 6.687 mol
H: 9.62 g / 1.00 g/mol = 9.62 mol
O: 10.14 g / 16.00 g/mol = 0.63375 mol

3) Ratio

C:6.687 / 0.63375 = 10.55
H: 9.62 / 0.63375 = 15.18
O: 0.63375 / 0.63375 = 1

Given that the tenth of C is 0.5 you need to multiply all the numbers by 2 =>

C: 10.55 * 2 = 21.1--> 21
H: 15.18 * 2 = 30.36 -> 30
O: 1 * 2 = 2

=> C21 H30 O2

Answer: C21 H30 O2