Water containing 0.1 m benzoic acid flows at 0.1 cm/s through a 1 cm diameter rigid tube of cellulose acetate. the walls of the tube are 0.01 cm thick and are permeable to small electrolytes like the acid. solutes within the tube wall diffuse as though moving through water. the tube is immersed in a large, well-stirred water bath containing negligible acid. after 50 cm of tubing, what fraction of the 0.1 m benzoic acid solution has been removed? the diffusivity of benzoic acid in water is 1´10-9 m2 /s.