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0.078g of a hydrocarbon occupy 28.414mL of volume at S.T.P.The empirical formula of the hydrocarbon is CH.The molecular formula of hydrocarbon is

$\begin{array}{1 1}(a)\;C_2H_2&(b)\;C_6H_6 \\(c)\;C_8H_8&(d)\;C_4H_4\end{array} $

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22.414mL of volume at STP is occupied by =0.078g of gaseous hydrocarbon
$\therefore$ 22400mL volume at STP is occupied by =$\large\frac{0.078g}{22.414mL}$$\times 22400mL=78$g gaseous hydrocarbon.
$\therefore$ Molar mass of hydrocarbon=78gmol$^{-1}$
Empirical formula mass of hydrocarbon $CH=12+1=13$
$\therefore n=\large\frac{\text{Molecular mass}}{\text{E.F.mass}}=\frac{78}{13}$$=6$
$\therefore$ Molecular formula of hydrocarbon =$(CH)_6=C_6H_6$
Hence (b) is the correct answer.
answered Mar 25, 2014 by sreemathi.v
edited Apr 2, 2014 by mosymeow_1

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