A gaseous alkane is exposed to oxygen. The volume of $O_{2}$ for complete combustion and the $C O_{2}$ formed are in the ratio $7 : 4$ . The molecular mass (in g) of the alkane is :

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Solution

Given that the gas is alkane and thus, its formula is $C_{n} H_{2 n + 2}$ .
For combustion,
$C_{n} H_{2 n + 2} [n + (n + 1) / 2] O_{2} \to n C O_{2} + (n + 1) H_{2} O$
$∴ \frac{V o l u m e o f O_{2} u s e d}{V o l u m e o f C O_{2} f o r m e d} = \frac{7}{4}$
$∴ \frac{[n + (n + 1) / 2]}{n} = \frac{7}{4}$
Therefore, $n = 2$ .
$A l k a n e i s C_{2} H_{6}$ .
The molar mass of alkane is $30$ g/mol.

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A gaseous alkane is exposed to oxygen. The volume of O2 for complete combustion and the CO2 formed are in the ratio 7:4. The molecular mass (in g) of the alkane is :

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