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Jul 12, 2023 · When a solution and a pure solvent are separated by a semipermeable membrane, a barrier that allows solvent molecules but not solute molecules to pass through, the flow of solvent in opposing directions is unequal and produces an osmotic pressure, which is the difference in pressure between the two sides of the membrane.
Reverse osmosis is a separation process that uses pressure to force a solvent through a semi-permeable membrane that retains the solute on one side and allows the pure solvent to pass to the other side, forcing it from a region of high solute concentration through a membrane to a region of low solute concentration by applying a pressure in ...
- A. Vapor Pressure Lowering. At any given temperature, the vapor pressure of a solution containing a nonvolatile solute is less than that of the pure solvent (see Section 10.3A for a discussion of vapor pressure).
- B. Boiling Point Elevation. The boiling point of a substance is the temperature at which the vapor pressure of the substance equals atmospheric pressure.
- C. Freezing Point Depression. Recall that freezing and melting point are two terms that describe the same temperature, the temperature at which the vapor pressure of the solid equals the vapor pressure of the liquid and at which the solid and the liquid are in equilibrium.
- D. Osmosis and Osmotic Pressure. Osmosis and osmotic pressure depend on the ability of small molecules to pass through semipermeable membranes like a thin piece of rubber, a cell membrane, or a thin piece of plastic wrap.
Applying a pressure greater than the osmotic pressure will reverse the osmosis. As we apply pressure to the concentrated side, the solvent will flow the other direction through the membrane resulting in pure solvent. One challenge with reverse osmosis is that as you produce pure solvent, the solution gets more and more concentrated.
Compared to pure water, a solution of hydrogen chloride is more acidic, a solution of ammonia is more basic, a solution of sodium chloride is more dense, and a solution of sucrose is more viscous. There are a few solution properties, however, that depend only upon the total concentration of solute species, regardless of their identities.
Oct 10, 2023 · The intramembrane pressure gradient drives water from the side with the lower osmolarity (pure solvent in Fig. 3) to the side with the higher osmolarity. In the narrow interface region on the high osmolarity side, the pressure drop by itself would drive water back toward the membrane, but in this region the Debye model shows that it is balanced ...
