Question

The weight of Methane which occupies the same volume at $STP$ as $7.5gm$ of Ethane is $2gm$

Answer 1

$\because PV=nRT$

$\Rightarrow V=\frac{nRT}{P}$

Let $W$ be the weight of methane

$\therefore$ For same volume, $\frac{\left(\frac{W}{16}\right)RT}{P}=\frac{\left(\frac{7.5}{30}\right)RT}{P}$

Since temperature and pressure conditions are same for both

$\therefore \frac{W}{16}=\frac{7.5}{30}$

$\Rightarrow W=4g$ .