Is With simple diffusion the rate of transport is proportional to the solubility of the substance.?

Yes, in simple diffusion, the rate of transport is indeed proportional to the solubility of the substance in the medium through which it is diffusing. Higher solubility generally allows more molecules to move across a membrane or through a solution, leading to an increased rate of diffusion. Additionally, factors such as concentration gradient and temperature also influence the overall rate of diffusion.