What factors affect the rate of diffusion?
There are many factors.
For example, temperature increases the rate of diffusion. If the temperature increases, the kinetic energy of the particles increases and therefore the movement of particles from an area of high concentration to an area of low concentration increases. In addition, the concentration difference also is another factor. If there's a large concentration difference between two areas -for example in a room if there's more perfume molecules in one side of a room than the other- then the rate of diffusion increases.
There are other factors that need to be considered, if this diffusion takes place across a membrane. And these are the surface area of the membrane and the thickness of it. The thinner the membrane the rate of diffusion increases because there's less space for the movement of these particles to move through. Also the larger the surface area of a membrane the faster diffusion takes place because there's a larger exchange surface.