Cycloalkane has a relative air vapor density of 1.931. Determine the molecular formula of this cycloalkane.

Let’s write down the solution:
1. Let’s designate the formula of a substance, hydrocarbon – CxHy.
2. Determine the molecular weight of the cycloalkane, if the density by air is known: M (air) = 29 g / mol;
3. Let’s make calculations:
M (CxHy) = D (air) * M (air) = 1.931 * 29 = 56 g / mol.
4. Let us establish the formula for organic matter, hydrocarbon:
СnH2n – general formula of cycloalkanes;
CnH2n = 56;
12n + 2 = 56;
12n = 54;
n = 4.5;
C4H8 – cyclobutane, M (C4H8) = 4 * 12 + 1 * 8 = 56 g / mol.
Answer: the molecular formula of the substance: C4H8 (cyclobutane).