Question

2130 D. HYDROLYSIS OF DISACCHARIDES and POLYSACOLARIDES Make sure you understand what you are doing bore Both the lodine Test and Benedict's best becau described below. Label test tubes so they are t s See the datatable for any that you pre heated in a hot waterbuch e e h 1. You will need 4 test tubes, 1 and 2 forstarch and dowe l of such to test tubes 1 and 2 Add a small pinch of sucrose to test tubes and 2. Test tube 1 is the control for starch test the 3 the wa y w e dded to test tubes land 3. To test tubes 1 and 3 add 20 drops of tap water 3. Add 20 drops of 10% HI to test tube 2 Istarch) and the same amount to test tube sucrose 4. Heat all 4 test tubes in a boiling water bath for 10 minutes 5. Remove the test tubes from the bath and allow them to cool. To the samples containing the HCI 2 and 4. add 20 drops of 10% NaOH to neutralize the aid of you added theme amount of H and NaOH to test tubes 2 and the samples should be neutralized if you are unsure, usimus paper to confirm that the solutions are no longer acidic). 6. Test all four samples to determine if hydrolysis occurred using the both the lodine Test and the Benedict's Test Using the samples in each of the test tubes, first remove s drops for the lodine test before adding Benedict's reagent to the samples. lodine Test: Using a spot plate, place 5 drops of each of the samples from test tubes 1, 2, 3, and 4) into separate wells. Add 1 drop of ladine reagent to each well. Record your observations and determine if hydrolysis has occurred. Record your observations and conclusions in the datatable. Benedict's test: Add 2 mL of Benedict's reagent to each of the test tubes and heat in a boiling water bath for 5 minutes. Record your observations and determine if hydrolysis has occurred. D. HYDROLYSIS WITH ACID (Results AFTER HEATING) Test tube 1: starch + water Test tube 2: starch + HCI Test tube 3: Sucrose water Test tube 4: Sucrose HCI lodine Test Observations: lodine Test Conclusions: polysaccharide present or not present Benedict's Test Observations: Benedict's Test Conclusions: reducing sugar present or no reaction QUESTION: In which test tubes did hydrolysis occur? V 025

Answer 1

1.

Iodine test:

Test tube1

Starch + water + Iodine gives positive test, blue colour formation of starch iodide. (no hydrolysis)

Conclusion: Polysaccharide present

Test tube2

Starch + HCl after boiling + Iodine gives negative test, blue colour is not formed. (Hydrolysis)

Conclusion: Polysaccharide is not present

Test tube3

Sucrose + water + Iodine gives negative test, blue colour blue colour is not formed.. (no hydrolysis)

Conclusion: Polysaccharide absent

Test tube 4

sucrose + HCl after boiling + Iodine gives negative test, blue colour is not formed. (Hydrolysis)

Conclusion: Polysaccharide absent

Benedict,s test

Test tube1

Starch + water + Benedict reagent + heating  gives negative test,no orange colour formed.

Conclusion: no reaction

Test tube2

Starch + HCl + Benedict reagent + heating  gives positive test and  orange colour formed. (Hydrolysis)

conclusion: reducing sugar glucose freed due to hydrolysis.

Test tube3

Sucrose + water + Benedict reagent + heating  gives negative test,no orange colour formed.

Conclusion: non reducing sugar

Test tube 4

Sucrose + HCl + Benedict reagent + heating  gives positive test and  orange colour formed.(Hydrolysis)

Conclusion:  reducing sugar glucose and fructose freed due to hydrolysis.