Question

A gas has molecular formula $(CH)_{n}$. If vapour density of the gas is $39$, what should be the formula of the compound?

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

Answer 1

Answer: (D)

Mol. wt. $= 2\times V.D = 2\times39 = 78 $
$\left(CH\right)_{n} = \left(13\right)_{n}$ or $13\times n =78 $
$ n ={78}/{13} = 6$
$ \therefore $ Molecular formula $= C_{6}H_{6}$