Derive the molecular formula of the hydrocarbon, the mass fraction of carbon in which is 83.3%.

| January 16, 2021 | education

Derive the molecular formula of the hydrocarbon, the mass fraction of carbon in which is 83.3%. the relative density of vapors of this substance in terms of hydrogen is 29.

Given:

w% (C) = 83.3%

D (H2) = 29

To find:

Formula -?

Decision:

1) Find the molecular weight of a substance by its density in terms of hydrogen:

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

Mr (HC) = D (H2) * Mr (H2) = 29 * 2 = 58

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

58 – 100%

x – 83.3%,

then x = 83.3% * 58: 100% = 48.

N (C) = 48: Mr (C) = 48: 12 = 4 atoms.

3) Then the molecular weight of hydrogen in the composition is 58 – 48 = 10.

N (H) = 10: Mr (H) = 10: 1 = 10 atoms.

We got a substance with the formula C4H10 – butane.

Answer: C4H10 – butane.



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