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. $C_2H_2$
• B. $C_6H_6$
• C. $C_8H_8$
• D. $C_4H_4$

Answer 1

Answer: (B)

$22.414\, mL$ of gaseous hydrocarbon at $S.T.P.$ has
mass $= 0.078 \,g$
$22414\, mL$ of gaseous hydrocarbon at $S.T.P.$ will
have mass $= 78\, g$
$\therefore $ Molar mass of hydrocarbon $=78\,g\,mol^{-1}$
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
$=(CH)_{6}$
$=C_{6}H_{6}$