Advanced Chemistry: Hydrolysis of Starch

AP/IB-II Chem: Hydrolysis of Starch Names:

Procedure: 1. Set up a 400 mL beaker with an immersion heater 2. Label four reaction vials 1,2,3,& 4. Label another four 1B, 2B, 3B and 4B. (Eight in all) 3. Label 3 vials X, Y and Z. Label another 4 vials XB, YB, & ZB 4. Add 5 mL of starch solution to a separate reaction vial (labeled “reaction”) * Add 2 mL of starch solution to vials X, Y and Z 5. Add 6 drops of concentrated sulfuric acid to the reaction vial using a glass pipet. * Add approximately 1 mL of saliva, (not phlegm balls) to vials X & Y, leave Z alone 6. Seal the vials tightly. Shake, to mix thoroughly 7. Suspend the vials (reaction vial and X) in the hot bath. Don’t heat Y or Z 8. Heat for 5 minutes, remove the reaction vial to cool. Leave X in the bath 9. Remove 1.0 mL of the starch solution from reaction vial and place in vial labeled 1. Seal both tightly. 10. Return the reaction vial to the hot bath, place vial #1 in a cool bath for a few minutes. 11. After cooling, add enough 1 M NaOH to vial #1 until the solution is neutral or slightly basic (~5 drops). Test with pH paper 12. Repeat steps 7-10 for vials 2, 3 & 4.

Analysis 13. Transfer half of the solutions in each of the vials (1-4) to their corresponding B vials (1B-4B). Vials 1-4 will be for the iodine test and the B vials will be for the Benedicts test. * Transfer half of the solution in vials X, Y and Z to corresponding B vials (XB, YB, ZB) 14. Place 2 drops of an iodine/potassium iodide solution into each of the vials labeled, 1-4, X, Y & Z Record your observations 15. Place 10 drops of Benedict’s solution in each of the vials labeled 1B-4B and XB, YB & ZB. Screw the Teflon caps back on the vials and place it into the boiling water for 5 minutes. Record your observations 16. All solutions can be poured down the drain with excess water 17. Clean and dry all vials.

Data Sample Iodine Test-Result Positive Test for: Benedict Test-Result Positive Test for: 1 2 3 4 X Y Z

Questions: 1. How did the concentration of starch in the reaction vial change with time? How do you know?

2. What happened to the starch as it was digested? How do you know?

3. What is the function of the enzyme Salivary amylase? How do you know?

4. What is the purpose of heating vial X? What happened to the amylase? How do you know?

5. What is the purpose of leaving vial Z alone?

Conclusion: Describe what the significance of this lab was.