IB HL BIOLOGY Dialysis Lab: Exploring Osmosis and Diffusion Through A Membrane
Dialysis is the flow of certain solutes through a semi permeable membrane. Dialysis is usually used on patients with failing kidneys to clinically purify blood in their kidneys, or other regions of their bodies. The dialysate contains waste matter that flows from the blood our of the dialysis tubing.
Question/aim of lab:
To test the solutions inside and outside the dialysis tubing with Benedict’s solution, Iodine reagent and silver nitrate solution to find out what has remained in the dialysis tubing, and which solutes have diffused through the semi permeable membrane and into the dialysate.
The sodium chloride will definitely pass through the semi permeable membrane because it is a very small molecule, compared to the large pores in dialysis tubing. Glucose and starch have bigger molecules, and therefore are less likely to pass through the dialysis tubing
250- mL beaker
12 test tubes (varied sizes)
200mm dialysis tubing
1.0% starch solution
10% glucose solution
5% sodium chloride solution
0.1M silver nitrate solution (in a dropper bottle)
PREPARING DIALYSIS TUBING
Place dialysis tubing in a beaker of water and allow it to soak for 5 minutes 2.
Take another beaker and fill it with enough water to submerged a filled dialysis tube 3.
Remove dialysis tube from water, open it, and tie one end into a knot 4.
Fill the tubing less that half way with 1.0% starch solution 5.
Fill the tubing to within 35mm with 10% glucose solution
Fill the tubing within 25mm to the top with 5% sodium chloride 7.
Tie the top of the tubing with the string
Rise off any spilled solution on the outside of the tubing 9.
Place the tubing in a beaker of distilled water
Let dialysis tubing remain inside for 1 day
Part I: Observation of solutions for testing for the presence of glucose, starch, and chloride (Table 1.1)
Using four test tubes, place 8 drops of the following into each test tube: a.
5% Sodium Chloride Solution
To each of these test tubes, add four drops of Benedict’s reagent to each tube and mix the test tube 3.
Record the initial color of the solutions
Place all four tubes into a beaker of boiling water
Record the color changes (if any) of the solutions
Repeat step one of Benedict’s test
Add four drops Iodine reagent to each of the four test tubes 3.
Record observations of solutions in each test tube
Repeat step one of Benedict’s test
Add one or two drops of 0.1 AgNO3 to each of the four tubes 3.
Record your observations of solutions in each test tube
Part II: Testing the dialysis experiment for the presence of glucose, starch, and chloride (Table 1.2) 1.
Fill 3 tubes with at least 50ml of the solution inside your dialysis tubing a.
Place four drops of Benedict’s reagent in tube A; record your observation b.
Place four drops of Iodine reagent in tube B; record your observation c.
Place four drops of 0.1 AgNO3 in tube C; record your observation 2.
Fill another 3 tubes with at least 50 ml of the solution in your dialysate a.
Place four drops of Benedict’s reagent in tube A1; record your observation b.
Place four drops of Iodine reagent in tube B1; record your observation c.
Place four drops of 0.1 AgNO3 in tube C1; record your observation
Table 1.1: Observation of solutions for testing for the presence of glucose, starch, and chloride
Cloudy (looks like a greyish purplish cloudy)
We can conclude the...
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