Question

A Compound whose molecular weigh is 103 analyzes as following (w/w%) C=81.5, H=4.9, N 13.6

What is Molecular formula of the compound.

Answer 1

Law of conservation of mass is the basis of material balance .

basis - 100gms of material .

C(atomic mass= 12) = 81.5/ 12 = 6.79gm. atoms

H(at. mass= 1) = 4.9 / 1= 4.9gm.atoms

N(at.mass= 14) = 13.6/ 14 = 0.97gm

dividing by the smallest no: (0.97) to make whole mumbers

C = 6.79/ 0.97 = 7 H= 4.9/ 0.97= 5 N= 0.97/0.97= 1

Emperical formula = C₇H₅N

Emperical formula weight = 7 x 12 + 5x1 + 1x 14= 103

Since emperical formula weight is equal to molecular formula weight so the molecular formula of the given compd is same as the emperical formula i.e C₇H₅N.

Molecular formula of the compd = C₇H₅N