Arrange the following gases in the increasing order of their densities at STP: `H_(2)`, air `CO_(2)`.

Explanation

The density of a gas at constant temperature and pressure, `d=(PV)/(RT)`.
Thus, at a particular temperature and pressure, the density of the gs is direclty proportional to the molar mass of the gas. The order of molar mass of the given gas is: `M_(H_(2)) lt M_(air) lt M_(CO_(2))`. therefore, the order of the desities of these gases at STP would be `d_(H_(2)) lt d_(air) lt d_(CO_(2))`.