Find the empirical formula and the molecular formula of an organic compound from the data given below:

Element	% composition	At. wt.	Relative no. of atoms	Simplest ratio
Carbon	75.92	12	$\frac{75.92}{12}$ = 6.32	$\frac{ 6.32 }{ 1.26}$ = 5
Hydrogen	6.32	1	$\frac{6.32}{1}$ = 6.32	$\frac{6.32 }{ 1.26}$ = 5
Nitrogen	17.76	14	$\frac{ 17.76}{14}$ = 1.26	$\frac{ 1.26}{ 1.26}$ = 1

Simplest ratio of whole numbers = C : H : N = 5 : 5 : 1

Hence, empirical formula is C₅H₅N

Empirical formula weight = 5(12) + 5(1) + 14 = 79

V.D. = 39.5

Molecular weight = 2 x V.D. = 2 x 39.5 = 79

$$\begin{aligned}\text{n} = \frac{\text{Molecular weight}}{\text{Empirical formula weight}} \\[0.5em] = \frac{79}{79} = 1\end{aligned}$$

∴ Molecular formula = n[E.F.] = 1[C₅H₅N] = C₅H₅N