Determine the molecular formula of the hydrocarbon, the mass fraction of carbon in which is 0.8824, and hydrogen – 0.1176.

Determine the molecular formula of the hydrocarbon, the mass fraction of carbon in which is 0.8824, and hydrogen – 0.1176. The relative density of the vapors of this substance in the air is – 2.3448

Given: W (C) = 0.8824;
W (H) = 0.1176;
D (air) = 2.344;
M (air) = 29 g / mol;
Find: ShNu -?
Decision:
1. Calculation of the molar mass of organic matter, if the density by air is known:
M (CxHy) = D (air) * M (air) = 30 * 2.3448 = 70.34 g / mol.
2. Determine the number of moles of carbon, hydrogen:
Y (C) = m / M = 88.24 / 12 = 7.35 mol;
Y (H) = 11.76 / 1 = 11.76 mol.
3. Consider the ratio:
X: Y = C: H = 7.35: 11.76 = 1: 1.6 = 1: 2 (divide by the smallest number 7.35):
The simplest formula – CH2 shows that the hydrocarbon belongs to alkenes.
4. Let’s make calculations, establish the formula based on the general: CnH2n;
CnH2n = 70.34;
12n + 2 = 70.34;
12n = 68.34;
n = 5.6;
C5H10
Verification:
M (C5H10) = 12 * 5 + 10 = 70 g / mol.
Answer: C5H10 – pentene.