As part of a bioseparations process, glucose (solute A) in aqueous solution (solvent B) is diffusing across a microporous membrane. The thickness of the membrane is 2.0 mm, and the pores running through the membrane consists of parallel cylindrical channels of 3.0 nm diameter (1 nm is a nanometer, 1 × 10⁹ nm = 1 m). The temperature is 30°C. The mean diameter of a single glucose molecule is 0.86 nm.

a. Estimate the molecular diffusion coefficient of glucose in water by the Stokes–Einstein relationship.

b. What is the effective diffusion coefficient of glucose through the membrane?