Print the molecular formula of a hydrocarbon, the mass fraction of hydrogen

| April 30, 2021 | education

Print the molecular formula of a hydrocarbon, the mass fraction of hydrogen in which is 20%, and the density of the hydrocarbon in air is 1.035.

Given:

w% (H) = 20%

D (= 1.035

To find:

Formula -?

Decision:

1) Let us find the molecular weight of the hydrocarbon by its density in air:

D (air) = Mr (HC): Mr (air), – since air does not have a certain molecular weight, it is conventionally taken as 29.

Mr (HC) = D (air) * 29 = 1.035 * 29 = 30

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

30 – 100%

x – 20%,

then x = 20% * 30: 100% = 6.

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

3) Then the molecular weight of carbon accounts for 30 – 6 = 24.

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

We got a substance with the formula C2H6 – ethane.

Answer: C2H6 is ethane.



One of the components of a person's success in our time is receiving modern high-quality education, mastering the knowledge, skills and abilities necessary for life in society. A person today needs to study almost all his life, mastering everything new and new, acquiring the necessary professional qualities.