Osmosis and Reverse Osmosis: Summary
The answers to the ConcepTests are given below and will open in a separate window.
Key points from this module:
- The osmotic pressure is proportional the molar concentration of solute species (i.e., if a solute molecule dissociates, the molar concentration of ions is used to calculate osmotic pressure).
- For reverse osmosis, the pressure difference (membrane side with the solute -membrane side with pure solvent) must be higher the osmotic pressure.
- As pressure on the membrane side with the solute increases, the flux through the membrane during reverse osmosis increases.
- Concentration polarization decreases the solvent flux through a membrane because the solute concentration near the membrane is higher than its concentration in the bulk.
- Mixing on the membrane side with a solute can decrease concentration polarization and thus increase solvent flux through the membrane.
From studying this module, you should now be able to:
- Calculate the osmotic pressure for a liquid mixture.
- Calculate molecular weight of a solute given the osmotic pressure of the solute.
- Explain how fugacity can be used to calculate the equation for osmotic pressure.
- Explain how reverse osmosis works to purify a mixture.
- Understand how concentration polarization affects permeation through a membrane
Additional Screencasts:
Osmotic Pressure for Nonideal Solutions
Calculate the Molecular Weight from Osmotic Pressure for Nonideal Solution
Calculate the Molecular Weight from Osmotic Pressure for Nonideal Solution
Prepared by John L. Falconer, Department of Chemical and Biological Engineering, University of Colorado Boulder