All three vessels are the same size and have the same capacity.

As a result, the pressure, volume, and temperature of each gas are the same.

The three vessels will each contain an equal quantity of the corresponding molecules, according to Avogadro’s law.

This number is equal to Avogadro’s number, that is, .

The relation gives the root mean square speed of a gas with mass and temperature :

Where,

is Boltzmann constant

For the given gases, and are constants

Therefore, depends only on the mass of the atoms, i.e.,

As a result, the root mean square speed of the molecules in each of the three scenarios differs.

The mass of neon is the smallest among neon, chlorine, and uranium hexafluoride.

As a result, among the supplied gases, neon has the fastest root mean square speed.