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

cl2
he
o2
ne

He

Explanation:

Movement of of gaseous molecules through tiny hole is called effusion.

At a given temperature, rate of effusion of gases is related with the molar mass (M) of the gases as:

Therefore, higher the molar mass of the gas, lower will the rate of effusion.

Molar mass of = 70 g/mol

Molar mass of He = 4.0 g/mol

Molar mass of = 32 g/mol

Molar mass of Ne = 20.17 g/mol

Since, molar mass of He is lowest among given, so rate of effusion of He will be the highest.