Chemistry 9 Lesson 55: Practice: Properties of glucose

1. Theoretical Summary

1.1. Experiment purpose

a. Knowledge

Experimentally, verify and deepen knowledge of the chemical properties of glucose.

b. Skill

– Practice chemistry skills, solve practical chemistry exercises, experiment with small amounts of chemicals.

– Practice observing, describing, explaining phenomena and writing chemical equations of experiments.

1.2. Experimental skills

• Take liquid chemicals with a dropper, do not transfer the dropper of one chemical bottle to another.
• When heating the test tube, it is necessary to heat the surrounding area until it is hot, then focus on heating to avoid breaking the test tube.
• Each experiment needs to take the correct amount and type of chemicals.
• When instilling the solution into the test tube, it should be done slowly, so that the phenomenon is clearly observed.
• Recover chemicals, wash test tubes, clean the laboratory after the end of the practice session.

1.3. Theoretical basis

• Effect of glucose on silver nitrate in ammonia solution:

OLD₆H_twelfthO₆ + Ag₂O \(\overset{NH_{3}}{\rightarrow}\) OLD₆H_twelfthO₇ (Gluconic Acid) + 2Ag\(\downarrow\)

• Distinguish between glucose, sucrose and starch:

Iodine adsorption into the empty slots in starch produces a blue-black color.

⇒ Method used to identify starch paste and vice versa (used to identify Iodine)

2. Conduct experiments

2.1. Experiment 1: Effect of glucose on silver nitrate in ammonia solution

a. Tools and chemicals

– Tools: Test tube, pipette, wooden clamp, alcohol lamp.

– Chemicals: solution of glucose, ammonia, silver nitrate.

b. Steps to take

– Add a few drops of silver nitrate solution to the ammonia solution in the test tube, shake gently.

– Then, add 1ml of glucose solution, shake gently, and gently heat it on the flame of an alcohol lamp (or put it in a cup of hot water).

– Observing the phenomenon.

c. Phenomena

There is a bright silvery substance that adheres to the walls of the test tube.

d. Explain

Due to Ag generated from the reaction on the wall of the test tube: C₆H_twelfthO₆ + Ag₂O \(\overset{NH_{3}}{\rightarrow}\) OLD₆H_twelfthO₇ (Gluconic Acid) + 2Ag\(\downarrow\)

2.2. Experiment 2: Distinguishing glucose, sucrose, starch

a. Tools and chemicals

– Tools: Test tube, pipette, wooden clamp, alcohol lamp.

– Chemicals: Glucose solution, sucrose, starch paste, AgNO . solution_3, ammonia.

b. Steps to take

There are 3 solutions of glucose, sucrose, and starch that are randomly numbered. Take each 1-2 ml solution into the corresponding numbered test tubes. Then conduct the following experiments:

– Step 1: Add 1-2 drops of iodine solution to 3 solutions in 3 test tubes. Observing the phenomenon.

– Step 2: Take 2 test tubes with numbers corresponding to the remaining 2 vials of solution, add 3ml of ammonia solution to each test tube, add 3 drops of AgNO solution₃ in and shake vigorously. Continue to add 3ml of solution in the corresponding vial into the test tube and then immerse the test tube in a beaker of hot water. Observing the phenomenon.

c. Phenomenon, explanation

– Step 1: For 3 test samples containing solutions of glucose, sucrose, and starch, respectively, react with the iodine solution.

• Phenomenon: In any jar that appears blue, it is starch. On the other hand, glucose and sucrose do not react.
• Explanation: Iodine blues starch lake.

– Step 2: Continue for the test sample containing the remaining 2 solutions to react with the AgNO3 solution in NH3.

• Phenomenon: In any vial that appears silvery colored substance clinging to the wall of the test tube, it is a solution of glucose, the remaining substance is sucrose.

OLD₆H_twelfthO₆ + Ag₂O → C₆H_twelfthO₇ + 2Ag

• Explanation: Glucose has a mirror reaction, Ag₂O in SMALL₃ Oxidizes glucose to gluconic acid and forms a silver precipitate on the wall of the test tube.

3. Conclusion

After the lesson to know:

• Ability to conduct experiments, observe reaction phenomena, explain and draw conclusions about the chemical properties of glucose.
• Confirm the correctness of the learned theory.
• Apply to explain related phenomena.
• Improve experimental skills, learn from experience for next time.