A flask of gaseous ${\mathrm{CCl}}_4$ was weighted at measured temperature and pressure. ${\mathrm{CCl}}_4$ was replaced by ${\mathrm{O}}_2$ at the same temperature and pressure. The mass of the ${\mathrm{CCl}}_4$ vapor will be

The molar mass of ${\mathrm{CCl}}_4\left({\mathrm{M}}_1\right)=154 \left(\mathrm{or}\right)$

The molar mass of ${\mathrm{O}}_2\left({\mathrm{M}}_2\right)=32$

${\mathrm{CCl}}_4$ when compared to${\mathrm{O}}_2$

12 + 71 × 2 

12 + 142

= 154 > 32

5 times as heavy has ${\mathrm{O}}_2$

$\frac{154}{32}=4.8125\simeq 5 times as heavy as O_2$

Hence ${\mathrm{CCl}}_4$ is approximately 5 times heavier than oxygen.