Question

In an organic compound of molar mass $108 g$ $mol ^{-1} C , H$ and $N$ atoms are present in 9: 1: 3.5 by weight. Molecular formula can be :

• A. $C _{6} H _{8} N _{2}$
• B. $C _{7} H _{10} N$
• C. $C _{5} H _{6} N _{3}$
• D. $C _{4} H _{18} N _{3}$

Answer 1

Answer: (A)

$C _{6} H _{8} N _{2}$

Answer 2

Molar mass $108 g$ Total part by weight $=9+1+3.5=13.5$ Weight of carbon $=\frac{9}{13.5} \times 108=72 g$ Number of carbon atoms $=\frac{72}{12}=6$ Weight of hydrogen $=\frac{1}{13.5} \times 108=8 g$ Number of hydrogen atoms $=\frac{8}{1}=8$ Weight of nitrogen $=\frac{3.5}{13.5} \times 108=28 g$ Number of nitrogen atom $=\frac{28}{14}=2$ Hence, molecular formula $= C _{6} H _{8} N _{2}$