Question

In a compoiu carbon and nitorgen are present in a ratio 3:1 by mass. Find out the molecular formula of the compound.(Atomic mass of C= 12u and Atomic mass of H=1 u).​

Answer 1

We have mass ratio of elements C : H: N = 9 :1 :3.5

Let us find the empirical formula of compound

Element

Atomic mass

Mass ratio

Relative number atoms

Simplest ratio

C

12

9

9/12 = 0.75

0.75 X4 = 3

H

1

1

1/1 = 1

1X4 = 4

N

14

3.5

3.5\14 = 0.25

0.25 X 4 = 1

Therefore, empirical fornula = C3H4N1

Now calculate the empirical formula mass= 3X 12 + 4X1 + 1 X 14 = 54

n = Molecular mass/ Empirical formula mass = 108/54 = 2

Moleclar formula = n X Empirical formula = 2 X C3H4N1

= C6H4N2