Question

The rate of diffusion of two gases a and b average kinetic energy

Answer 1

An important thing to keep in mind here is that you're dealing with rates of diffusion, not with rates of effusion. Because the two gases are presumably kept under the same conditions for pressure and temperature, you can find a relationship between their rates of diffusion and their molar masses.

Now, according to Graham's Law of Diffusion, the rate of diffusion of a gas is inversely proportional to the square root of its density