Derive the molecular formula of the hydrocarbon if the mass fraction of carbon is 80% hydrogen 20%

Derive the molecular formula of the hydrocarbon if the mass fraction of carbon is 80% hydrogen 20% relative density by hydrogen-15 name the resulting hydrocarbon

Given:

w% (C) = 80%

w% (H) = 20%

D (H2) = 15

To find:

Formula -?

Decision:

1) Find the molecular weight of the compound by its hydrogen density:

D (H2) = Mr (UV): Mr (H2)

Mr (HC) = D (H2) * Mr (H2) = 15 * 2 = 30

2) Knowing the mass fraction of carbon, we find its molecular weight in the composition and the number of atoms:

30 – 100%

x – 80%,

then x = 80% * 30: 100% = 24.

N (C) = 24: Mr (C) = 24: 12 = 2 atoms.

3) Then the molecular weight of hydrogen in the composition is 30 – 24 = 6.

N (H) = 6: Mr (H) = 6: 1 = 6 atoms.

We got a substance with the formula C2H6 – ethane.

Answer: C2H6 is ethane.