Let us assume that there are 100 grams of substance present. The masses of the constituents will be:
C - 58.51 g
H - 7.37 g
N - 100 - 58.51 - 7.37 = 34.12 g
Next, we determine the moles of each substance by dividing by the atomic masses:
C - 58.51/12 = 4.88
H - 7.37/1 = 7.37
N - 34.12/14 = 2.44
Dividing all of the moles by the lowest number of moles, which is 2.44 of nitrogen, we get the ratio:
C - 2
H - 3
N - 1
The empircal formula becomes C₂H₃N
Next, we apply Graham's Law of diffusion, which mathematically is:
v₁/v₂ = √M₂ / √M₁
Let species 1 be helium, meaning v₁/v₂ = 3.2 and M₁ = 4
3.2 = √M₂ / √4
M₂ = 40.96
The mass of the empircal formula was:
12 * 2 + 1 * 3 + 14 = 41
The empircal formula is the molecular formula as their masses are approximately the same. This compound is C₂H₃N
