Four tyres of a motor car were filled with nitrogen, hydrogen, helium and air. In which order are these tyres to be filled with the respective gases again?

Explanation

According to Graham's law of diffusion, under the same conditions of temperature and pressure, the rate of diffusion of a gas is inversely proportional to the square root of its molar mass. The order of molar masses of the given gases is-
`M_(H_(2)) lt M_(He) lt M_(N_(2)) lt M_(air)`
At the same temperature and pressure, the order of rates of diffusion of these gases would be `-r_(H_(2)) gt r_(He) gt r_(N_(2)) gt r_(air)`
After a certain time, the order of decrease in pressure in these tyres, tyre(air) `lt` tyre`(N_(2))lt`tyre (He) `lt` tyre `(H_(2))`.
Hence, tyres are to be filled again with the respective gases in the followig order, tyre `(H_(2))`, tyre (He), tyre`(N_(2))`, tyre `(air)`.