Which of the following gases will have the highest rate of effusion at a given temperature?

Cl2

He

O2

Ne

He

Explanation:

Because it has the lowest molar mass out of all the choices.

He.

Explanation:

Graham's law states that the effusion rate is inversely proportional to the molecular weight. It means that the gas with the lowest molecular weight will have the highest effusion rate.

The molecular weights of the given gases are:

Cl₂ = 70.9 g/mol.

He = 2.0 g/mol.

O₂ = 32.0 g/mol.

Ne = 20.17 g/mol.

Since He has the smallest molecular mass, so it will have the highest rate of effusion.