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Published byNicholas Riley Modified over 2 years ago

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Diffusion and Osmosis

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Diffusion and Osmosis Overview You will investigate diffusion and osmosis in a model membrane system You will investigate the effect of solute concentration on water potential as it relates to living plants.

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Concentration Effect

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Molarity C 6 H 12 O 6 = glucose Sucrose = 2 glucose C 6 H 12 O 6 + C 6 H 12 O 6 = C 6 H 12 O 6 - H 2 O = C 12 H 22 O 11 so Using the periodic table, you can calculate GFM of sucrose (342g)

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So to make 500 ml of solution……. 0.0 Molar = 342g x 0 x M = 342 x.2 x.5 etc

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Prepare dialysis bags…… Add sucrose solutions to bags Mass carefully Place in distilled water for 30 minutes Re-mass Calculate the % change in mass

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Final Mass-Initial Mass Initial Mass X 100 To Calculate the % change in mass:

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Period 4 Lab 1B Data % Change In Mass Period 6 M ABCDEClass av

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Period 5 Lab 1B Data % Change In Mass Period 6 M ABCDEClass av

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Period 4 Lab 1C Data

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Period 5 Lab 1C Data

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Contents in Beaker% Change in Mass Distilled Water M Sucrose M Sucrose M Sucrose M Sucrose M Sucrose Lab 1C: Ideal Class Data

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LinearFit for: Data Set Percent Change in Mass

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Water Potential In Potato Cells Osmosis is a special type of diffusion. It is the movement of water molecules through a selectively permeable membrane from a region of higher water potential to an area of lower water potential Water potential is the measure of free energy of water in a solution Water always moves to a more negative water potential.

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Water Potential = p + s Where there is no % change in mass, the solution in the beaker has the same water potential as the potato cells. ( = p + s ) = ( = p + s ) Beaker Potato p = 0 (open beaker) so s

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To Calculate s See page 13 of the lab s = -iCRT i = Ionization constant (sucrose is 1.0 because it does not ionize). C = Molar Concentration (from line of best fit where the line crosses the x axis) R = Pressure Constant ( liter bars/mole °K T = Temperature °K (273 + °C)

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So lets say the line of best fit crosses the x axis at 0.36…….. s = -iCRT s = -(1.0)(0.36 mole/liter)( liter bar/mole ° K)(295 ° K) bars This equals the entire of the cell

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