You have been asked to evaluate the likely effectiveness of geomembrane liners used to underlie a hazardous waste pond to preventing xylene from leaching into the underlying soil. A consultant proposes to use a 1mm thick linear low density polyethylene (LLDPE) plastic sheet for retaining the xylene which is present at ppm levels in the wastewater. To be considered effective, the plastic sheet must retain the xylene for at least 20 years. Aminabhavi and Naik (J. Haz. Mater. 1998, 60, 175-203) deduced the molecular diffusivities of several alkanes in plastics including LLDPE. Plotting their data as a function of molar volumes, they found the following regression equation: logDttopt=3.5logV+0.63 where diffusivity in LLDPE, DILDPE, is in cm2s1 and molar volume in cm3mol1. The molar volume of xylene, Vxylene,=100cm3mol1. You decide to define chemical breakthrough as the time it takes for the half-concentration distance to become larger than the thickness of the plastic membrane. This can be expressed as t1/2=2Dix1/22 a. Will a 1mm thick LLDPE sheet be effective at retaining xylene for 20 years? b. How thick of a LLDPE sheet would be need to retain xylene for exactly 20 years? c. How far would xylene diffuse in water in 20 years if molecular diffusion was the only transport process