Comparing the effusion rate of oxygen and hydrogen, which one is faster and why?

Relative molecular mass of O₂, M(O₂) = 16.0 × 2 g/mol = 32.0 g/mol
Relative molecular mass of H₂, M(H₂) = 1.0 × 2 g/mol = 2.0 g/mol

Graham’s law of effusion : The ratio of the rates of effusion of two gases at the same temperature and pressure is equal to the inverse ratio of the square roots of the masses of the gas particles, i.e.

Effusion rate of O₂ : Effusion rate of H₂
= √(Relative molecular mass of H₂) : √(Relative molecular mass of O₂)
= √2.0 : √32.0
= (√2.0 × √1) : (√2.0 × √16)
= √1 : √16
= 1 : 4

Effusion rate of H₂ is faster.

lighter means faster (if at the same temp)

At the same temp both gases have the same kinetic energy (KE)

KE = 1/2mv^2
m = mass
v = velocity

To end up with the same KE, the molecule with the lower mass has to have higher velocity.

Well hydrogen bombs do kill a lot more people than oxygen does.