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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 C6H12O6 = glucose Sucrose = 2 glucose C6H12O6 + C6H12O6 =**

C6H12O6 - H2O = C12H22O11 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 .5 0.2 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**

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

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Period 4 Lab 1B Data % Change In Mass Period 6 M A B C D E Class av. 1.0 0.8 0.6 0.4 0.2 0.0

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Period 5 Lab 1B Data % Change In Mass Period 6 M A B C D E Class av. 1.0 0.8 0.6 0.4 0.2 0.0

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Period 4 Lab 1C Data

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Period 5 Lab 1C Data

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**Lab 1C: Ideal Class Data Contents in Beaker % Change in Mass**

Distilled Water 21.4 0.2 M Sucrose 6.9 0.4 M Sucrose - 4.5 0.6 M Sucrose - 12.8 0.8 M Sucrose - 23.0 1.0 M Sucrose - 23.5

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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 = Yp + Ys**

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

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**To Calculate Ys See page 13 of the lab Ys = -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……..**

Ys = -iCRT Ys = -(1.0)(0.36 mole/liter)( liter bar/mole ° K)(295 ° K) -8.83 bars This equals the entire Y of the cell

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Tendency of water to favor one side more than another. Water moves from an area of high potential to low potential. Predicts which way water diffuses.

Tendency of water to favor one side more than another. Water moves from an area of high potential to low potential. Predicts which way water diffuses.

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