Question

A container has 3 gases whose mass ratio is 1:3:5. What is the ratio of mean square speed of the molecules of two gases? Their atomic masses are 20u, 30u & 40u corresponding to the order in which the ratios are given.

(a) 2:3:4

(b) 4:3:2

(c) 2:√3:√2

(d) √2:√3:2

I had been asked this question by my school principal while I was bunking the class.

This is a very interesting question from Kinetic Theory of an Ideal Gas topic in chapter Kinetic Theory of Physics – Class 11

Answer 1

The correct option is (b) 4:3:2

The best I can explain: Their average kinetic energies will be the same.                                                                                    Thus, 1/2mv^2will be the same.

v1^2:v2^2:v3^2 =m3:m2:m1

= 40:30:20

= 4:3:2.