# Determine the molecular formula of the amine mass fraction of carbon 38.7%, nitrogen 45.15%

**Determine the molecular formula of the amine mass fraction of carbon 38.7%, nitrogen 45.15%, hydrogen 16, 15% .. D (H2) = 15.5**

Mass ratio of elements in unknown amine:

w (C): w (H): w (N) = 38.7: 16.15: 45.15

Taking into account the atomic masses of the elements, let’s move on to the quantitative ratio:

n (C): n (H): n (N) = w (C) / M (C): w (H) / M (H): w (N) / M (N) =

38.7 / 12: 16.15 / 1: 45.15 / 14 = 3.225: 16.15: 3.225 = 1: 5: 1

This means that in the molecule of the unknown amine there are 5 hydrogen atoms and 1 nitrogen atom per carbon atom. Thus, the formula for this compound can be written as: CnH5nNn.

Molecular weight of unknown amine:

M (CnH5nNn) = M (H2) * DH2 (CnH5nNn) = 2 * 15.5 = 31 (amu).

Let’s compose and solve the equation:

12 * n + 1 * 5n + 14 * n = 31

31n = 31,

n = 1, whence the formula of this amine: CH5N, which corresponds to methylamine (CH3NH2).