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Anonymous users2024-02-16There are many heated containers: 1 test tube is used to hold a small amount of medicine, and a container for a small amount of reagent reaction at room temperature or heating, which can be used to make and collect a small amount of gas.
Precautions for use: Can be heated directly. Do not quench after heating to prevent explosion. The mouth of the test tube should not be pointed at anyone when heating; When heating the solids, the tube should be placed horizontally with the nozzle slightly inclined downward.
2 Beaker Used as a reaction vessel for dispensing solutions and enlarged reagents, at room temperature or when heated.
Precautions for use: When heating, it should be placed on the asbestos net to make the heating even. When the dissolved substance is stirred, the glass rod must not touch the wall or bottom of the cup.
3 Flask The container used for a large amount of reagent and a liquid substance to participate in the reaction can be divided into round-bottomed flasks, flat-bottomed flasks and distillation flasks. They can all be used to assemble gas generators. Distillation flasks are used to separate miscible substances with different boiling points.
Precautions for use: Round-bottom flasks and distillation flasks can be used for heating, with asbestos netting when heating, and can also be used in other hot baths (such as water bath heating, etc.). Do not add more than half the volume of the flask.
4 Evaporation dish is used to evaporate liquids or concentrate solutions.
Precautions for use: It can be heated directly, but not quenched. The volume of liquid should not exceed 2 3
Crucible pliers should be used to take and place the evaporation dish.
5 Crucibles are mainly used for high-temperature burning of solid substances.
Precautions for use: Place the crucible on the mud triangle on the tripod and heat it directly. Crucible pliers should be used to take and place crucibles.
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Anonymous users2024-02-15Direct heating: test tubes, crucibles, evaporation dishes.
Mesh heating: beakers, flasks, Erlenmeyer flasks.
Cannot be heated: gas collection cylinders, reagent bottles, Qipu generators, drop bottles.
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Anonymous users2024-02-14Test tubes, crucibles, evaporation dishes (the above can be heated directly), beakers, Erlenmeyer flasks, flasks (they need to be heated with asbestos nets).
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Anonymous users2024-02-13Crucibles, evaporation dishes, beakers, test tubes.
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Anonymous users2024-02-12Direct heating: test tubes, crucibles, evaporation dishes.
Mesh heating: beakers, flasks, Erlenmeyer flasks.
Cannot be heated: gas collection cylinders, reagent bottles, Qipu generators, drop bottles.
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Anonymous users2024-02-11Test tubes, crucibles, evaporation dishes (the above can be heated directly), beakers, Erlenmeyer flasks, flasks (they need to be heated with asbestos nets).
There are 8 books in the human education version, which are compulsory: >>>More
1) The most intense non-metallic element that reacts with water is f >>>More
The total pressure of the container increases because the number of molecules of the gas increases, the volume does not change, and the pressure increases. However, it can be considered that the pressure of the original reaction system remains unchanged, which involves the problem of partial pressure, or the pressure is understood from the perspective of the concentration of the substance, the concentration of reactants and products does not change, and the pressure of the reaction system does not change. >>>More
If high school students want to learn high school chemistry well, they should not only rely on careful listening in class to improve their chemistry scores, but also rely on timely consolidation after class to help them complete a deeper understanding of chemistry. In addition to the consolidation of knowledge points, high school students should also review and summarize their classroom listening status, high school students can summarize their classroom listening status from the record of their class notes, and then reflect on their own shortcomings in the lectures, and remind themselves to correct them in time, and look for something similar to Chengdu 211Educate such training schools, develop plans with the help of professionals, and learn high school chemistry with methods and skills.
In this reaction, there is only the electron gain and loss of nitrogen element, the valency has risen and decreased, so C is wrong, the increase of nitrogen in metadimethylhydrazine is oxidized, it is a reducing agent, so a is wrong, the reaction is the recombination of atoms, so there is an endothermic and exothermic process, C is wrong, D is left, of course, there are eight electrons transferred from two N2O4 to N2 D is correct.