reduction by hydrogen, ethanol, vitamin C · aluminum-glucose
This time I will talk about reduction. Since ancient times, being able to handle metals has been a measure of that civilization. In the stone age before dealing with metal, copper was smelted, bronze ware made by mixing tin with copper, and in the Iron Age, and nowadays it has changed to rare earths. By the way, metals rarely come out of the ground as they are, and often come out in the form of oxides. Removing the oxygen from the oxide is called reduction. In junior high school, copper oxide is generally reduced with carbon, but this time we will introduce various reduction reactions.
Experiment 1: Reduction of copper oxide with hydrogen
Set up a test tube that stores hydrogen. The copper wire is coiled and heated. It becomes black copper oxide. If you put this in a test tube containing hydrogen while it is hot, the copper will be reduced and returned to the original copper. If you put it out while it is hot, it will become copper oxide again due to the air.
Experiment 2: Reduction of copper oxide with ethanol
Prepare copper oxide. (Please heat the copper powder and prepare it.) Place it on a plate of aluminum foil. This is to prevent the test tube and copper powder from sticking together. Soak cotton wool with ethanol. Place in a test tube and heat both alternately with an alcohol lamp. Copper oxide is reduced and returned to copper powder. A metallic luster can be seen by rubbing with the bottom of the test tube.
The chemical reaction formula is CuO + C2H5OH (ethanol) → Cu + CH3CHO (acetaldehyde) + H2O
However, for students, hydrogen in ethanol reduces copper oxide to copper. I think the explanation is fine. In addition, aromatic products such as naphthalene can also be used.
In junior high school, the reaction of taking reduced equal oxygen from a substance is always paired with oxidation. So far, but I'm going to high school. And, we handle redox by exchanging electrons. Oxidation: Loses electrons. Reduction: Receives an electron. It will be.
Experiment 3: Reduction of iodine with vitamin C
Iodine is present in solution in the form of I2. It is reduced by Vitamin C. In this case, it receives an electron and I- . It becomes an ion of (reduced). Drop the lemon juice into the iodine solution to make it transparent.
Experiment 4: Thermite reaction
It is a method to reduce the metal oxidized with metallic aluminum. Please be careful as it emits tremendous energy. First, as shown in the photo on the left, mix the metal oxide and aluminum powder, and place the magnesium ribbon in the center to facilitate the reaction. If you ignite it, a violent reaction will occur.
This reaction is used when welding railroad tracks and other railroad tracks outdoors because it is easy to do.
Experiment 5: Reduction of methylene blue by glucose (reducing sugar)
you need : 4 g of glucose, 2 g of sodium hydroxide, a little methylene blue, 200 ml of water, PET bottle
Completely dissolve sodium hydroxide and add glucose there. Adding methylene blue turns the solution blue. After a while, it is reduced by glucose to become a clear liquid. Therefore, glucose is called reducing sugar. When shaken, it is oxidized by oxygen in the air and turns blue again. You can repeat the experiment several times. Adjust the reagents just before the experiment.
Experiment 6: Reduction with glucose (reducing sugar) ②
you need : glucose 4g, sodium hydroxide 2g, indigo carmine 1% 4ml, water 200ml, PET bottle
Completely dissolve sodium hydroxide as in Experiment 5, then add glucose. It turns green when indigo carmine solution is added. It turns yellow after about 20 minutes. When shaken lightly, it is oxidized by oxygen in the air and turns reddish brown. If you shake it further, it will be oxidized again and turn green. After this, it is reduced by glucose and changes from reddish brown to yellow and calms down. You can do this experiment several times. However, please do not shake it too violently. Adjust the reagents just before the experiment.
