Of these gases, which has the fastest-moving molecules (on average) at a given temperature? -N2
-They all have the same average speed.
-Cl2
-HCl

Which gas molecules have the highest average kinetic energy at a given temperature?
-They all have the same average kinetic energy.
-Cl2
-HCl
-N2

a) N2

b) They all have the same average kinetic energy.

Explanation:

At a given temperature, the speed of a gas molecule depends on its relative molecular mass. The heavier the gas, the lesser its average velocity at a given temperature. On that basis, N2 molecules are the fastest moving gas molecules.

At a particular temperature, all gases have the same average kinetic energy.