If the four tubes of a car are filled to the same pressure with \[N_{2},O_{2},H_{2} and Ne\]   separately, then which one will be filled first ?
a) \[N_{2}\]
b) \[O_{2}\]
c) \[H_{2}\]
d) Ne

Answer: c
Explanation: Lesser the density more is the volume and H₂ has lowest density. ( d =   \[\frac{MP}{RT}\]   at constant P, R and T, d   \[\propto\]   M )