Molecular formula of alkene, the mass fraction of carbon in which is 85.7%. The relative density of this substance

Molecular formula of alkene, the mass fraction of carbon in which is 85.7%. The relative density of this substance for nitrogen is 2.

Let’s execute the solution. Let’s write down the data on the condition of the problem:
1. Given: СnH2n – alkene;
W (C) = 85.7%
D (N2) = 2;
M (N2) = 28 g / mol;
Find: ShNu -?
2. Determine the molar mass of the hydrocarbon:
M (CxHy) = M (N2) * D (N2) = 28 * 2 = 56 g / mol.
3. Let’s calculate the amount of carbon, hydrogen:
Y (C) = 85.7 / 12 = 7.14 mol;
m (C) = 7.14 * 12 = 85.68 g;
m (H) = 100 – 85.68 = 14.32 g;
Y (H) = m / M = 14.32 / 1 = 14.32 mol.
4. Ratio:
C: H = 7.14: 14.32 = 1: 2;
Simplest formula: CH2
5. Let’s establish the molecular formula:
CnH2n = 56;
12n + 2 = 56;
n = 4.5;
C4H8;
Checking: M (C4H8) = 12 * 4 + 1 * 8 = 56 g / mol.
Answer: C4H8 is butene.