1) Calculate the rms speed of an oxygen gas molecule, O2, at 17.0 ?C . Express your answer numerically in meters per second.

2) Rank the following gases in order of decreasing rate of effusion

C3H8, He,CO, H2, Ar

We know the rms velocity of a compound is squar root of (3RT/M)

Molar mass of oxygen = 32g/mol = 32x 10^-3 Kg/mol

R = 8.314 J/K.mol

Thus RMS velocity = square root of [3x8.314x290/32x10^-3]

= 475.43m/sec

2) The rate of diffsion of gases is inversely proportional to the square root of density of the gas according to Graham's law.

Since density is proportional to molar mass, we can say rate of diffusion/effusion is inversely proportional to the molar mass.

Thus the higher the molar mass, the less is the rate of effusion.

order of molar mass of the given gases is H2 (2)< He(4) < CO(28) < Ar(40) < C3H8(44)

Thus the order of decreasing rate of effusion is  H2 (2)> He(4) > CO(28) > Ar(40) > C3H8(44)