Question

In an organic compound of molar mass 108 gram/mole C, H, and N atoms are present in 9:1:3.5 by weight find out the molecular formula of the compound

Answer 1

The ratios of the weights of the elements present in the compound are given.

Let us assume that the weight of:

C = 9x
H = 1x
N = 3.5x

therefore,
9x+1x+3.5x = 108
x = 8

Mass of C in the compound= 9x = 9*8 = 72 g
Mass of H in the compound= 1x = 8 g
Mass of N in the compound= 3.5x = 3.5*8 = 28 g

We can calculate the number of moles from the mass of the element in the compound,

Number of moles of C in the compound = 72/12 = 6
no. of moles of H in the compound = 8/1= 8
no. of moles of N in the compound = 28/14 = 2

Thus the ratio of the moles of each element is C:H: N=6:8:2

.Hence the molecular formula of the compound is $C_6{H}_8{N}_2$.