Joe Udel lives on the second floor of a house that is adjacent to a well of pure water, but city water comes out of his indoor plumbing. He would rather have pure well water. So he has developed the following scheme. He will mount a pipe from the well up the side of his building into a tank in the third-floor attic. The bottom of the pipe will contain a membrane permeable to water, but not to the 1000-molecularweight polymer he will add to the pipe (he is proposing to use a low-molecular-weight polymer so that the mixture viscosity will not be too high). He will add enough of the polymer so that water in the pipe will rise to the top of the tank, a height of 15 meters. The end of the pipe in the attic will have a second membrane of the same type at its base, so that water exiting the membrane will drip into a second tank open to the atmosphere. In this way the polymer will remain in the system, and Joe will have pure well water from the second tank. A diagram of the proposed process (with water dripping from tank 1 to tank 2) is shown. 

a. How much polymer (in kg per kg water) is needed for this process? 

b. Does the process violate the second law of thermodynamics? Will this process work indefinitely without any external power?

Transcribed Image Text:

15 m Well Tank 1 with semipermeable membrane at its base Tank 2 containing fresh water Pipe with semipermeable membrane at its base