BITSAT 2013 Paper

RMS velocity of molecules depends on mass. If mol. wt. increases, rms velocity of melocules decreases.
rms α

1

√m.wt.

The order of increasing m. wt. is
H2 < N2 < O2 < HBr
Order of Vrms of molecules.
HBr < O2 < N2 < H2