Hydrolysis of sucrose
Materials
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Measuring cylinder ± 1 ml
Pipette ± 1 ml
2 test tubes
Beaker
1M sucrose solution
1M hydrochloric acid
1M sodium hydroxide
Benedict´s solution
Phenolphthalein indicator
Method:
1.
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8.
Measure 3ml of 1M sucrose solution into two test tubes
Label one test tube as the control and the other as your experiment
Add 1ml of 1M hydrochloric acid (HCl) with a pipette to the test tube labelled as your experiment
Place both tubes in a water bath at 90°C for 10 min
Remove test tubes from water bath and cool until the solutions have reached room temperature
Add 3 drops of phenolphthalein to the test tube marked as your experiment
Neutralize the solution in this test tube by slowly pipetting in 1M sodium hydroxide (NaOH) until the solution in the test tube
remains pink. Agitate the tube after each addition of NaOH
Add 2ml of Benedict´s solution to each test tube and complete the Benedict´s test
Results
Solution
Initial colour after adding
Benedict´s reagent
Result of Benedict´s test
Control
Sucrose +HCl
Conclusion
What is the purpose of adding the hydrochloric acid?
What is the purpose of neutralizing the solution with NaOH before carrying out the Benedict´s test
What do the results of the Benedict´s test prove?
What is the purpose of a control?
Are reducing sugars present?
Hydrolysis of starch
Materials
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Measuring cylinder ± 1 ml
Pipette ± 1 ml
12 test tubes
Beaker
Stop watcher ±0.01s
1M starch solution
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1M hydrochloric acid
1M sodium hydroxide
Benedict´s solution
Iodine solution
Phenolphthalein indicator
Spot tile
Method
1.
Label your 12 test tubes as follows
Control - 0
Control - 10
Control - 20
Control - 30
Control – 40
Control - 50
A-0
A - 10
A - 20
A - 30
A - 40
A - 50
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Measure 3ml of starch solution into each test tube
In every test tubes labeled ‘A’ add 1M HCl with a pipette
Place all the test tubes into a water bath at 90°C for 50 min apart from the tubes marked ‘0’
Remove a drop of solution out of both tubes and test for iodine
Add 2ml of Benedict´s solution to the control test tube and complete the Benedict´s test
To the remainder of test tube ‘A -0’ add 3 drops of phenolphthalein
Neutralize the solution in the test tube by slowly pipetting in 1M sodium hydroxide (NaOH) until the solution in each test
tube remains pink. Agitate the tube after each addition of NaOH
9. Add 2ml of Benedict´s solution to the ‘A -0’ test tube and complete the Benedict´s test
10. Repeat steps 5-8 every 10 min for both the control tube and the experimental ‘A’ tube for 50 min
Results
Test for starch
Colour of solution after time (±0.01s)
0
10
20
30
40
50
Colour of solution after time (±0.01s)
0
10
20
30
40
50
Solution
Control
A -Starch + HCl
Test for reducing sugar
Solution
Control
A -Starch + HCl
Conclusion
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What do your results prove?
Why did you carry out a control?
If you wanted to repeat this experiment to make it suitable for an internal assessment how could you improve it?