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Effect of concentration on diffusion rate experiment
Rate of diffusion experiment
Rate of diffusion experiment
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Diffusion Lab
Problem
Will starch, water, glucose, iodine or a combination of the above diffuse across the membrane of the dialysis bag causing the bag to either expand or shrivel?
Hypothesis & Strategy
I believe that the smaller molecules, such as glucose and water will diffuse through the dialysis bag’s membrane causing it to expand, due to the concentration gradient. I would test this hypothesis by filling the bag with a solution consisting of water, glucose and starch, tie it off and weigh it. I would then place the bag in a beaker of water and let it sit for a day. Then I would reweigh the bag.
Materials
· Dialysis Tubing
· Glucose Starch Solution, 15mL
· IKI Solution, 5mL
· 4 Glucose Indicator Strips
· 1 Graduated Cylinder
· 1 Plastic Cup, 250mL
Experimental Procedure
1. Pour 15mL prepared glucose/starch solution into the graduated cylinder.
2. Get a piece of tubing and use a sting to tie a knot on one end of the tubing.
3. Open the tubing and pour 15mL of the glucose/starch solution into the tubing.
4. Determine the initial glucose content in the tubing by using the glucose indicator strip. Record the data in Table 1.
5. Tie another not at the other end, leaving room for expansion
6. Record the color of the solution in the bag in Table 1.
7. Fill a 250mL beaker approximately 2/3 full with distilled water. Add 5mL of iodine to the beaker.
8. Record the color of the solution in Table 1.
9. Determine the beaker glucose content using the glucose indicator strip and record the data in Table 1.
10. Completely immerse the dialysis bag in the solution in the beaker.
11. Wait at least 30 minutes or until there is a noticeable change in the color of the solution in either the beaker or the dialysis bag.
12. Remove the dialysis bag from the beaker reweigh it and record the final color and glucose content of the dialysis bag and the beaker. Record this data in Table 1.
13. Wash your hands and clean up lab area.
Observations
Color Glucose Content Bag
Time Dialysis Bag Beaker Dialysis Bag Beaker Weight
Start Cloudy white Gold 500 mg/dl Negative 49.5g
After 30 minutes Cloudy Purple Clear 100 mg/dl 100 mg/dl 50.9g
Analysis
1. What do your observations tell you about the presence of glucose, starch, and IKI in the dialysis bag and the beaker before and after the experiment?
Before the experiment the dialysis bag had water with glucose and starch dissolved in it, while the solution in the beaker consisted of water and iodine. After the experiment the iodine had diffused into the bag while the glucose had diffused out of the bag. This is evident because at the conclusion of the experiment the bag was purple due to the reaction of iodine and starch.
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