Question

A compound contains $92.3$% carbon and $7.7$% hydrogen. The molecule of the compound is $39$ times heavier than hydrogen molecule. The molecular formula of the compound is:

• A. $C_3{H}_3$
• B. $C_2{H}_2$
• C. $C_2{H}_4$
• D. $C_6{H}_6$

Answer 1

The correct option is D $C_6{H}_6$

Let the Empirical formula be $C{H}_x$.
So, $\frac{12}{12+x}\times 100=92.3⟹x=1$
Empirical formula $=CH$
Empirical formula weight $=13$
Molecular weight $=$ $2\times 39=78$
$\frac{MW}{EW}=\frac{78}{13}=6$
$\text{Molecular formula}=(\text{Empirical formula}{)}_6$
Thus, the molecular formula of the compound is $C_6{H}_6$.