Set the molecular formula of a hydrocarbon containing 84% carbon if 500ml of its vapor has a mass of 2.232g.

Given:
CxHy
ω (C in CxHy) = 84%
V (CxHy) = 500 ml = 0.5 l
m (CxHy) = 2.232 g

To find:
CxHy -?

Decision:
1) ρ (CxHy) = m (CxHy) / V (CxHy) = 2.232 / 0.5 = 4.464 g / l;
2) M (CxHy) = ρ (CxHy) * Vm = 4.464 * 22.4 = 100 g / mol;
3) Mr (CxHy) = M (CxHy) = 100;
4) ω (H in CxHy) = 100% – ω (C in CxHy) = 100% – 84% = 16%;
5) N (C in CxHy) = (ω (C in CxHy) * Mr (CxHy)) / (Ar (C) * 100%) = (84% * 100) / (12 * 100%) = 7;
6) N (H in CxHy) = (ω (H in CxHy) * Mr (CxHy)) / (Ar (H) * 100%) = (16% * 100) / (1 * 100%) = 16;
Unknown substance – C7H16.

Answer: Unknown substance – C7H16.