Question

The empirical formula of a compound is $CH$. Its molecular weight is $78$. The molecular formula of compound will be

• A. $ C_{2}H_{2} $
• B. $ C_{6}H_{6} $
• C. $ C_{3}H_{3} $
• D. $ C_{4}H_{4} $

Answer 1

Answer: (B)

Molecular formula
$=(\text { empirical formula })_{n} $
$n=\frac{\text { molecular weight }}{\text { empirical formula weight }}$
$\because$ The empirical formula of compound $= CH$
$\therefore $ Empirical formula weight $=13$
Molecular weight $=78$
$n=\frac{78}{13}=6$
Hence, molecular formula
$=(\text{ empirical formula })_{n}$
$=( CH )_{6}= C _{6} H _{6}$