Osmosis and Osmotic Pressure

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Osmosis and Osmotic Pressure

• Honors ChemistryMrs. Coyle

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Osmosis (Animation)

• http//highered.mcgraw-hill.com/sites/0072495855/s
  tudent_view0/chapter2/animation__how_osmosis_works
  .html

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Osmosis

• The flow of solvent molecules through a
  semipermeable membrane from the less concentrated
  side (less solute) to the more concentrated side
  (more solute).
• A semipermeable (porous) membrane allows certain
  molecules to go through it, in part due to their
  small size (ex. water molecules).
• Application artificial kidney dialysis (solvent
  and small solute (waste ) particles flow through
  the membrane).

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Osmotic Pressure

• The volume and pressure increase on the side of
  high solute concentration.

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• At equilibrium, the pressure exerted by the
  increased volume is called osmotic pressure.
• Osmotic pressure is also the amount of pressure
  necessary to stop osmosis.

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Measuring Osmotic Pressure(Thistle Tube)
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Reverse Osmosis

• The application of an external pressure greater
  than the osmotic pressure on the solution side of
  the semipermeable membrane, results in a net flow
  of sovent from the solution to the solvent side.
• Application desalination of seawater

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Osmotic Pressure

• ?MRT
• ? osmotic pressure
• M molarity of solute particles
• T absolute temperature
• R universal gas constant
• (0.0821 atm L / mol K or 62.3 mmHg L / mol K
  or8.31kPa L / mol K)

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Example 1 Determine ?

• Determine the osmotic pressure of 20.mL of a
  water solution containing 0.20 g of hemoglobin at
  37?C. The molar mass of hemoglobin is 6.41x104 g.
• ?MRT
• Answer M1.56x10-4M, ?4.0x10-3atm

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Example 2Determine Molar Mass

• . The osmotic pressure of a water solution
  containing 0.0070 g of a compound in 0.0010L of
  solution was 3.0 mmHg at 20.?C. Determine the
  molar mass of the compound.
• Answer 4.3x104 g/mol