The relative hydrogen density of the unknown alkane is 8.00. Determine the molecular formula of the alkane.

Let’s execute the solution:
By the condition of the task, we write the data:
1. Given: CxNu – hydrocarbon, alkane;
D (H2) = 8;
M (H2) = 2 g / mol;
Determine: molecular formula.
2. Let’s calculate the molar mass:
M (CxHy) = D (H2) * M (H2) = 8 * 2 = 16 g / mol.
3. Let us establish the formula based on the general for alkanes:
CnH2n + 2 = 16;
12n + 2 + 2 = 16;
12n = 16 – 4;
12n = 12;
n = 1;
CH4;
Checking: M (CH4) = 12 + 4 = 16 g / mol.
Answer: methane – CH4.