Question

In a compound C, H and N atoms are present in 9 : 1 : 3.5 by weight. Molecular weight of compound is 108. Molecular formula of compound is
(a) C₂H₆N₂
(b) C₃H₄N
(c) C₆H₈N₂
(d) C₉H₁₂N₃.

Answer 1

Mass of 1 mole of compound = 108g.

Let the mass of C in 1 mole of compound = 9x.

mass of H in 1 mole of compound = x

mass of N in 1 mole of compound = 3.5x

therefore total mass = 9x+x+3.5x = 13.5x.

According to the question

13.5x=108

=> x=108/13.5 = 8.

mass of C=9x=72g = 12(6)

mass of H= x= 8g = 1(8)

mass of N=3.5x=28g = 14(2)

molar mass of C,H,N = 12, 1, 14.

therefore there are 6, 8, 2 molecules of C,H,N

(c) C6H8N2