AP EAPCET 25-Aug-2021 Shift 2 Paper

The average molecular speed is inversely proportional to the square root of molar mass.
v=√

8‌RT

πM

i.e.v∝−

1

√M

Among O2,CO2, He and NH3, He has very low molar mass. Therefore, it has greatest average velocity.
Order of molar mass (g∕mol) is

CO2

44.01

>O2

32.0

<

NH3

17.03

>

He

4.002

Order of average velocity is He>NH3>O2>CO2. Hence, helium has the greatest average speed of its molecules.