How many cyclic color changing reactions, cyclic discoloration?

The silica gel will turn blue after absorbing moisture, but it can be used again after processing and drying. You can do whatever you want, as long as it's dry.

The test tube contains a fuchsa solution of sulfur dioxide that is colorless, and the mouth of the test tube is closed with a balloon. When heated, the solution turns red, and when cooled, it becomes colorless.

The test tube contains a phenolphthalein solution with ammonia in red, and the mouth of the test tube is closed with a balloon. When heated, the solution is colorless, and when cooled, it turns red.

Heating copper sulfate crystals (with crystal water, blue) turns into white anhydrous copper sulfate, which is stored in the air for a long time, absorbs water vapor, and turns blue... Beg.

Phenomenon: When a cup of prepared solution is placed on the table, the color of the solution changes color in a cyclic between colorless, amber, and blue.

Method: Before the performance, the performer takes three beakers, puts 102 5 ml of 3095 hydrogen peroxide in the first beaker, dilutes it to 250 ml with distilled water, puts 10 7 grams of potassium iodide in the second beaker, and adds 10 ml of sulfuric acid with a concentration of 2 moles, dilutes 250 ml with distilled water in a group, puts 0 075 grams of starch in the third beaker, and pours a small amount of water, heats it to boiling, makes the starch completely dissolved, and then weighs 3 9 grams of malonic acid and 0 845 grams of manganese sulfate, Place in a third beaker and dilute to 250 ml with distilled water. Then the performer takes three 50 ml graduated cylinders, measures 50 ml of the solution in each of the three beakers, first pours the 50 ml solution of the first beaker into a 200 ml beaker, and then puts the first.

Pour 50 ml of solution from two or three beakers into this 200 ml beaker and cover the top of the beaker with a towel. During the performance, the performer puts the beaker covered with a towel on the table, opens the towel, and the audience sees that the color of the solution changes from colorless to amber, from amber to blue, and then from blue to colorless......The solution will change color in cycles.

Principle: The reason why the color in the above performance changes so much is determined by the nature of hydrogen peroxide. When the solution is colorless, hydrogen peroxide can be used as a reducing agent, it reduces the iodine in the iodic acid to elemental iodine, and the elemental iodine can make the starch solution blue, when the solution turns blue, the hydrogen peroxide can be used as an oxidant, so that the elemental oxidation of iodine into alcoholic acid, so that the blue in the solution fades, and the solution becomes colorless ......This cycle causes the color of the solution to change periodically.