Question

The gas having average speed four times as that of SO2 (molecular mass 64) is ___________

(a) He(molecular mass 64)

(b) O2(molecular mass 4)

(c) H2(molecular mass 32)

(d) CH4(molecular mass 16)

I had been asked this question in an international level competition.

Enquiry is from Ideal Gases topic in portion Kinetic Theory of Gases of Engineering Physics I

Answer 1

Right answer is (a) He(molecular mass 64)

The explanation: vrms=√(3RT/M)

v1/v2 =√(M2/M1)

v/4v=√(M2/64)

M2=4

Hence the gas is He which has molecule mass 4.