Which are heavier and ligher than air: `O_(2),CO_(2),CH_(4),NH_(3),Cl_(2)` ? [Volumetric composition of air: `N_(2)=74%,O_(2)=24%,CO_(2)=2%`]

Explanation

Vapour density of a gas `=("molecular mass of gas")/("molecular mass of air")`
Volumetric composition of air:
`=((28xx74)+(32xx24)+(2xx44))/(100)=29.28`
Therefore, with respect to air, vapour densities of
`O_(2)=(32)/(29.28)gt1, CO_(2)=(44)/(29.28) gt 1,CH_(4)=(16)/(29.28) lt 1,`
`NH_(3)=(17)/(29.28) lt and Cl_(2)=(71)/(29.28) gt1`
`therefore` Gases ligher than air are `CH_(4)` and `NH_(3)` whereas gases heavier than air are `O_(2),CO_(2) and Cl_(2)`.