What affects the rate of diffusion?

I haven’t worked with this in a long time but does mass affect diffusion?

Size of Molecules.
Shape of molecules.
The concentration gradient.
Temperature.
Charge.
Lipid Solubility.
Always remember, the molecule with lesser Mr value will diffuse faster.

By lesser Mr value , do you mean the one with the lower molar mass?

Yes. By Mr value I meant molar mass.

Molecular weight/Mr is how much mass each particle has (how heavy it is). The heavier the particle, the slower it is going to move (assuming energy of the system remains constant).

For Example:
Methylene blue has a molecular weight about twice that of KMnO4 so it should take about twice as long to diffuse.

Awesome I totally get what your saying. It actually makes sense.