Question

An organic compound was found to contain carbon = 40.65%, hydrogen = 8.55% and Nitrogen = 23.7%. Its vapour density was found to be 29.5. What is the molecular formula of the compound?

Answer 1

Empirical formula = C₂H₅NO 

Molecular mass = 2 x (vapour density) 

= 2 x 29.5 

= 59.0 

Empirical formula mass of C₄H₅NO = 24 + 5 + 14 + 16 

= 59 

n = (Molecular mass) / (Empirical formula mass)

= 59/59 = 1 

Empirical formula mass = 59 

\(\therefore\)  Molecular formula = (Empirical formula)_n 

= (C₂H₅NO)₁ 

Molecular formula = C₂H₅NO