# A gaseous alkane was exploded with oxygen.The volume of $O_2$ for complete combustion to $CO_2$ formed was in the ratio of 7 : 4.The molecular formula of alkane is

$\begin{array}{1 1}(a)\;CH_4&(b)\;C_2H_6\\(c)\;C_3H_6&(d)\;C_4H_{10}\end{array}$

$C_nH_{2n+2}+(n+\large\frac{n+1}{2})$$O_2\rightarrow nCO_2+(n+1)(H_2O)$
$\large\frac{Volume\;of\;O_2\;used}{Volume\;of\;CO_2\;formed}=\frac{7}{4}$
$\large\frac{n+(n+1)/2}{n}=\frac{7}{4}$
$\therefore n=2$
And alkane is $C_2H_6$
Hence (b) is the correct answer.