Find the molecular formula of a hydrocarbon, the mass fraction of hydrogen in which is 10%.

Find the molecular formula of a hydrocarbon, the mass fraction of hydrogen in which is 10%. The relative density of a substance for hydrogen is 20.

1. The hydrocarbon formula is expressed by the general composition: CxHy;

2. Let us express the molar mass of the unknown hydrocarbon:

M (CxHy) = DH2 * M (H2);

3. M (CxHy) = 20 * 2 = 40 g / mol;

4.y * Ar (H) = w (in shares) * M (CxHy);

5.y * Ar (H) = 0.1 * 40 = 4;

6. Let’s define what the index y is equal to:

y = 4: 1 = 4;

7.x * Ar (C) = M (CxHy) – y * Ar (H);

8.x * Ar (C) = 40 – 4 = 36;

9.x = 36: 12 = 3;

10.The formula for the desired hydrocarbon is:

CxHy = C3H4.

Answer: C3H4.