Question

An unknown hydrocarbon compound was analyzed for hydrogen by elemental analysis and results show that it contains 15.88 % H. What is the empirical formula? C4H9 C8H18 C12H27

Answer 1

If H = 15.88%

Then C = 100.00 – 15.88 = 84.12%

Divide each % value by respective atomic mass

H = 15.88/1 = 15.88

C = 84.12/12 = 7.01

Divide through by smaller value

H = 15.88/7.01 = 2.26

C = 7.01/7.01 = 1

Remove fraction , multiply by 4

H = 9

C = 4

Empirical formula = C4H9

The hydrocarbon could be ( C4H9)2 = C8H18 = octane.