Question

The ratio of the vapour densities of two gases at a given temperature is $9:8$. The ratio of the rms velocities of their molecules is

• A. $3:2\sqrt{2}$
• B. $2\sqrt{2}:3$
• C. $9:8$
• D. $8:9$

Answer 1

The correct option is B $2\sqrt{2}:3$

Here, ρ1ρ2=98ρ1ρ2=98
vrms=3RTM−−−−−√vrms=3RTM
At a given temperature
(vrms)1(vrms)2=M2M1−−−−√=ρ1ρ2−−−√=89−−√=22√3