What property of gas molecule affects the speed at which it diffuses?

Helium and Ethlyene Oxide. Your answer is MASS.

Explanation:

Diffusion is faster at higher temperatures because the gas molecules have greater kinetic energy. effusion refers to the movement of gas particles through a small hole. Graham's law state's that the effusion rate of a gas is inversely proportional to the square root of the mass of its particles.

Answer: Temperature

Explanation: Temperature of gas molecules affect the speed at which it diffuses. Diffusion is faster at higher temperatures because the gas molecules collide more often with each other and therefore have greater kinetic energy to diffuse.