The relative density of vapor of alkane for hydrogen is 15. Derive the molecular formula of alkane.

The relative molecular weight of hydrogen is 2 g / mol. Let’s find the relative molecular weight of the alkane:
2 * 15 = 30 g / mol;
The general formula for alkanes is as follows: CnH2n + 2.
The relative atomic mass of carbon is 12, hydrogen is 1. To find the formula, we compose the equation:
12n + 2n + 2 = 30;
12n + 2n = 30 – 2;
14n = 28;
n = 28/14;
n = 2;
If n = 2, then 2n + 2 = 2 * 2 + 2 = 6.
Answer: The molecular formula of alkane is C2H6.