Question

Which gas has more diffusion?

Answer 1

Hint: To find out which gases have more diffusion, one must understand what all are the factors in gases which determine the diffusion rate. Whether these factors vary inversely or directly with the diffusion also determine the rate.

Complete answer:
Diffusion is the net movement of anything from the region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in concentration. Unless the equilibrium is obtained, diffusion will continue from higher concentration to lower concentration. The particles collide with each other or with the container, thus changing directions, eventually spreading throughout the container. Liquid and gases undergo diffusion as molecules are able to move randomly. This constant state of random motion (translations, rotational, vibrations) and collision with each other is known as kinetic energy. As gases possess kinetic energy therefore they undergo diffusion.
The rate of diffusion depends upon Graham's law. Graham’s law states that the rate of diffusion or effusion is inversely proportional to the square root of the molar mass of the particles or its molecular weight. This law is only approximate for diffusion of one gas in another or in air, as these processes involve movement of more than one gas. This also means that the gas which has the least molecular weight will diffuse the fastest as there is an inverse relation between molecular weight and rate of diffusion. Thus we can say that gas like Helium will have a higher rate of diffusion as its molecular weight is low.

Note:
Kinetic energy of the gases depends upon the temperature. This implies that all molecular movement ceases if the temperature is reduced to absolute zero. Also during collision of two molecules, total kinetic energy is conserved.