Question

0.078 g of a hydrocarbon occupy 22.414 mL of volume at S.T.P. The empirical formula of the hydrocarbon is CH. The molecular formula of the hydrocarbon is CH. The molecular formula of hydrocarbon is

• A. $C_2{H}_2$
• B. $C_6{H}_6$
• C. $C_8{H}_8$
• D. $C_4{H}_4$

Answer 1

Answer: (B)

$22.414mL$ of gaseous hydrocarbon at $S.T.P.$ has
mass $=0.078g$
$22414mL$ of gaseous hydrocarbon at $S.T.P.$ will
have mass $=78g$
$\therefore$ Molar mass of hydrocarbon $=78gmo{l}^{-1}$
Empirical formula mass of hydrocarbon $(CH)$
$=12+1=13$
$\therefore$ $n=\frac{\text{Molecular mass}}{\text{E.F. mass}}=\frac{78}{13}=6$
$\therefore$ Molecular formula of hydrocarbon
$=(CH{)}_6$
$=C_6{H}_6$