Establish the molecular formula of organic matter if, when burning this substance weighing 29 grams. formed 88 g

Establish the molecular formula of organic matter if, when burning this substance weighing 29 grams. formed 88 g of CO2 and 45 g. H2O. The relative density of this substance in the air is 2

Given:
m (in-va) = 29 g
m (CO2) = 88 g
m (H2O) = 45 g
D air. (in-va) = 2

To find:
in -?

Decision:
1) n (CO2) = m (CO2) / M (CO2) = 88/44 = 2 mol;
2) n (C) = n (CO2) = 2 mol;
3) m (C) = n (C) * M (C) = 2 * 12 = 24 g;
4) n (H2O) = m (H2O) / M (H2O) = 45/18 = 2.5 mol;
5) n (H) = n (H2O) * 2 = 2.5 * 2 = 5 mol;
6) m (H) = n (H) * M (H) = 5 * 1 = 5 g;
7) m (O) = m (in-va) – m (C) – m (H) = 29 – 24 – 5 = 0 g;
8) CxHy;
9) x: y: z = n (C): n (H) = 2: 5;
C2H5;
10) M (in-va) = D air. (in-va) * M (air) = 2 * 29 = 58 g / mol;
11) M (C2H5) = Mr (C2H5) = Ar (C) * N (C) + Ar (H) * N (H) = 12 * 2 + 1 * 5 = 29 g / mol;
12) M (in-va) / M (C2H5) = 58/29 = 2;
(C2H5) 2 – C4H10.

Answer: Unknown substance – C4H10.