Summary of senior high school chemistry experiment

Many students want to learn chemistry well today, so they are eager to do problems and read books. But first of all, it needs to be clear that high school chemistry is divided into several categories. Generally speaking, high school chemistry is summarized by charts. Today, I compiled a summary of high school chemistry experiments for you. Come and have a look with me!

Summary of senior high school chemistry experiment

Seven principles of chemical experiment operation

If you master the following seven principles about the operation sequence, you can correctly answer the "judgment question of experimental procedure".

1, "bottom-up" principle

Taking the Cl2 laboratory method as an example, the sequence of assembling the generator is as follows: placing the iron frame → placing the alcohol lamp → fixing the iron ring according to the position of the alcohol lamp → asbestos mesh → fixing the round bottom flask.

2. The principle of "from left to right"

Assembling complex equipment follows the order from left to right. The assembly sequence of the above devices is: generator → gas container → beaker.

3. The principle of "blocking" before "fixing"

Plug the stopper with a catheter before fixing the flask, so as to avoid damaging the instrument due to improper force or excessive force after fixing the flask.

4, "solid first" principle

In the above example, the reagent MnO2 in the flask should be put in before fixing the flask to avoid damaging the flask when putting in solids. In short, solid reagents should be added to the corresponding containers before fixation.

5. "After adding liquid" principle

The liquid medicine is added after the flask is fixed. As in the above example, after the flask is fixed, concentrated hydrochloric acid should be slowly added into the separating funnel.

6, prior air tightness (before filling the cartridge) principle

7. Principle of lighting alcohol lamp after installation (lighting alcohol lamp after installation of all equipment).

two

Application of Thermometer in Chemical Experiment

1. Measuring the temperature of the reaction mixture: This kind of experiment needs to measure the accurate temperature of the reaction mixture, so a thermometer should be inserted in the middle of the mixture.

① Measure the solubility of substances. ② Laboratory ethylene production.

2. Measuring the temperature of steam: This kind of experiment is mostly used to measure the boiling point of substances. Since the temperature of liquid and steam is the same when the liquid is boiling, it is only necessary to measure the temperature of steam.

① Laboratory distillation of petroleum. ② Determine the boiling point of ethanol.

3. Measuring the temperature of the water bath: In this kind of experiment, as long as the temperature of the reactants remains relatively stable, the water bath is used for heating and the thermometer is inserted into the water bath.

(1) Effect of reaction temperature on reaction rate. ② Nitration of benzene.

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Common experiments that need to plug cotton

Heating potassium permanganate to produce oxygen, producing acetylene and collecting NH3.

Its function is to prevent potassium permanganate powder from entering the catheter; Prevent the foam produced in the experiment from pouring into the catheter; Prevent ammonia from convection with air, thus shortening the time for collecting NH3.

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Separation and purification methods of common substances

1, crystallization and recrystallization: the solubility of substances in solution varies greatly with temperature, such as NaCl and KNO3.

2. Distillation cooling method: boiling point difference is large. In ethanol (water): new CaO is added to absorb most of the water, and then distilled.

3. Filtration method: soluble and insoluble.

4. Sublimation method: silica (I2).

5. Extraction method: For example, use CCl4 to extract I2 from I2 water.

6. dissolution method: Fe powder (A 1 powder): dissolve in excess NaOH solution, and filter and separate.

7. Addition method: the impurities are converted into the required substances: CO2(CO): by hot CuCoO2 (SO2): by sodium bicarbonate solution.

8. Absorption method: To remove the gas impurities in the mixed gas, drugs must be used to absorb the gas impurities: N2(O2): the mixed gas absorbs O2 through the copper mesh.

9. Conversion method: it is difficult to separate the two substances directly, but it is easy to separate them by adding chemicals, and then they are reduced back: Al(OH)3, Fe(OH)3: firstly, NaOH solution is added to dissolve Al(OH)3, and then filtered to remove Fe(OH)3, and then acid is added to convert NaAlO2 into A 1(OH)3.

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10 Common methods for removing impurities

1, impurity transformation method:

In order to remove phenol from benzene, sodium hydroxide can be added to convert phenol into sodium phenolate, which can be separated from benzene by dissolving in water. NaHCO3 in Na2CO3 can be removed by heating.

2, absorption washing method:

To remove a small amount of hydrogen chloride and water mixed in carbon dioxide, the mixed gas can first pass through saturated sodium bicarbonate solution and then through concentrated sulfuric acid.

3, precipitation filtration method:

Removing a small amount of copper sulfate mixed in ferrous sulfate solution, adding excessive iron powder, fully reacting, and filtering to remove insoluble substances to achieve the goal.

4, heating sublimation method:

This method can be used to remove sand from iodine.

5, solvent extraction method:

This method can be used to remove a small amount of bromine contained in water.

6. Solution crystallization (crystallization and recrystallization):

In order to remove a small amount of sodium chloride from sodium nitrate solution, the solubility difference between them can be used to reduce the solution temperature, so that sodium nitrate crystals can be precipitated and pure sodium nitrate crystals can be obtained.

7. Fractional distillation method: To remove a small amount of alcohol in ether, the method of multiple distillation can be adopted.

8, liquid separation method:

This method can be used to separate immiscible liquid mixtures with different densities, such as benzene and water.

9, dialysis method:

This method can be used to remove ions from colloid. Such as removing chloride ions from iron hydroxide colloids.

10, comprehensive method:

In order to remove impurities in substances, the above methods can be used or combined.

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15 "No" in basic operation of chemical experiment

1. Drugs in the laboratory should not be touched by hand; Don't put your nose to the mouth of the container to smell the gas, let alone taste the crystals.

2, after the experiment, the remaining drugs shall not be discarded, and don't put back in the original bottle (except active metal sodium and potassium).

3. When taking the potion, open the cork and don't put it on the table; The label on the bottle should face the center of the hand, not down; When put back, the label should not be inward.

4. If the skin accidentally spills concentrated H2SO4, don't rinse it with water first, wipe it off quickly with a cloth according to the situation, and then rinse it with water; If acid or alkali spills into your eyes, never rub your eyes with your hands, and try to deal with it in time.

5, weighing drugs, can't put the weight directly on the tray; You can't put the weight on the right plate; Don't hold it by hand when adding code.

6. Do not put the dropper into the measuring cylinder (test tube) or touch the cylinder wall (test tube wall) when adding liquid with the dropper. 7. When adding alcohol to the alcohol lamp, it shall not exceed 2/3 of the volume of the alcohol lamp and shall not be less than 1/3.

8. Don't point the burning alcohol lamp at another alcohol lamp; Don't blow with your mouth when you go out.

9. When heating substances, the inner flame and flame center of alcohol lamp shall not be used.

10, when heating the test tube, don't press your thumb on the short handle; Never point the test tube mouth at yourself or others; In general, the volume of liquid should not exceed 1/3 of the volume of test tube.

1 1. When heating the flask, don't forget to put an asbestos net on it.

12, after heating with crucible or evaporating dish, do not take it back directly by hand, but clamp it with crucible pliers.

13. When using a glass container for heating, don't let the bottom of the glass container touch the wick to avoid the container from breaking. Don't wash very hot glass containers with cold water, and don't put them on the table to avoid cracking.

14. When filtering liquid, the liquid level in the funnel should not be higher than the edge of the filter paper to avoid impurities entering the filtrate.

15. Never put the flask on the table and force the cork into it to avoid crushing the flask.

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In the chemical experiment, 22 cases came first and then came.

1. When heating the test tube, it should be heated evenly first, and then locally.

2. When collecting gas by drainage, first take out the catheter and withdraw the alcohol lamp.

3, gas, check the air tightness before charging.

4. When collecting gas, exhaust the air in the device before collecting.

5. When diluting concentrated sulfuric acid, put a certain amount of distilled water in the beaker, and then slowly inject concentrated sulfuric acid along the wall.

6. When igniting combustible gases such as H2, CH4, C2H4 and C2H2, check the purity before igniting.

7. When testing halogen elements of halogenated hydrocarbon molecules, add dilute HNO3 to the hydrolysis solution, and then add AgNO3 solution.

8. When testing NH3 (with red litmus test paper), Cl2 (with starch KI test paper), H2S[ with Pb(Ac)2 test paper] and other gases, wet the test paper with distilled water before contacting the gases.

9. When doing the reaction experiment between solid drugs, grind them separately first and then mix them.

10. When preparing easily hydrolyzable salt solutions such as FeCl3 _ 3 _ 3 and SnCl2 _ 2, first dissolve them in a small amount of concentrated hydrochloric acid and then dilute them.

1 1. In the neutralization titration experiment, the burette washed with distilled water is wetted with standard solution before being loaded with standard substance; Before removing the liquid, wetting and cleaning with the liquid to be detected; When reading the burette, wait a minute or two before reading; When observing the color change of the solution in the conical flask, wait for half a minute, and the color remains unchanged, which is the titration end point.

12, flame reaction experiment, burn platinum wire with dilute hydrochloric acid on the flame until it is colorless every time, and then do the next experiment.

13. When reducing CuO with H2, firstly introduce H2 flow, then heat CuO, after the reaction, remove the alcohol lamp, and stop introducing H2 after cooling.

14. When preparing the concentrated solution of the substance, first add distilled water to the graduation line of the volumetric flask with a beaker, and then add water to the graduation line with a rubber dropper.

15. When installing the generator, the following principles should be followed: bottom-up, first left and then right or first down and then up, first left and then right.

16, concentrated H2SO4 accidentally splashed on the skin, first quickly dry it with a cloth, then rinse it with clear water, and finally apply 3%-5% NaHCO3 solution. When stained with other acids, it should be washed with water first, and then coated with NaHCO3 solution.

17, lye on the skin, rinse with water before applying boric acid solution.

18. When acid (or alkali) flows to the dining table, first add NaHCO3 solution (or acetic acid) to neutralize it, then rinse it with water, and finally wipe it with a cloth.

19. When checking whether sucrose, starch and cellulose are hydrolyzed, first add NaOH solution to neutralize H2SO4, and then add silver ammonia solution or Cu(OH)2 suspension.

20. When using pH test paper, first dip the solution to be tested with a glass rod and coat it on the test paper, and then compare the color of the test paper with the standard colorimetric card to determine the pH value. ..

2 1. When preparing and storing salt solutions that are easily hydrolyzed and oxidized by air, such as Fe2+ and SN2+; Boil distilled water first to drive away O2, then dissolve it, and add a small amount of corresponding metal powder and corresponding acid.

22. When weighing drugs, first put two pieces of paper with the same size and weight on each plate (corrosive drugs are put in glassware such as beakers), and then put drugs. The heated medicine should be cooled first and then weighed.

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The position of catheter and funnel in the experiment

Catheters and funnels are used in many chemical experiments. Therefore, whether their positions in the experimental device are correct or not directly affects the experimental results, and the specific requirements are different in different experiments. The following plan combines the experimental pictures in the experiment and chemistry textbooks to make a brief analysis and induction.

1, conduit in gas generating device; The parts in the container can only be exposed a little or parallel to the rubber plug, otherwise it is not conducive to exhaust.

2. When gas is collected by exhaust method (including upward and downward), the conduit must extend to the vicinity of the bottom of the container or test tube. This is beneficial to exhaust the air in the gas cylinder or test tube and collect relatively pure gas.

3. When collecting gas through drainage, the conduit only needs to reach the mouth of the gas container or test tube. The reason is that "how much the catheter extends into the gas cylinder and the test tube does not affect the gas collection", but compared with the two, the former is convenient to operate.

4. When doing the experiment of the reaction between gas and solution, the catheter should extend to the middle and lower part of the solution container. This is conducive to the contact and full reaction of the two.

5. When igniting H2, CH4, etc. To prove that water is generated, not only a big and cold beaker is used, but also the catheter should be 1/3 extended into the beaker. If the catheter extends into the beaker too much, the generated droplets will evaporate quickly, and as a result, no water droplets can be observed.

6. When conducting the experiment of one gas burning in another gas, the conduit for igniting the gas should be placed in the center of the container containing another gas. Otherwise, if it collides with the bottle wall or gets too close, the high temperature generated by combustion will make the gas container burst.

7. When the steam generated by heating method is condensed and collected in the test tube, the conduit mouth must always keep a certain distance from the liquid level in the test tube to prevent the liquid from being sucked back into the reactor through the conduit.

8. If water-soluble gases such as HCl and NH3 need to be directly injected into the water for dissolution, it is necessary to connect an inverted funnel on the conduit and slightly immerse the edge of the funnel in the water, so as to avoid the experiment failure caused by water being sucked into the reactor.

9. The conduit for the inlet of the washing cylinder must be inserted into the middle and lower part of the solution, so that the impurity gas can fully react with the solution and be removed. The air supply conduit must be flush with the plug or slightly longer to facilitate air exhaust.

10. When making H2, CO2, H2S, C2H2 and other gases, in order to add acid or water conveniently, a long-necked funnel can be installed on the stopper of the container, and the funnel neck must be inserted below the liquid level to avoid air leakage. 1 1. When preparing Cl2, HCl and C2H4 gases, a funnel can also be installed on the plug of the reactor to facilitate acid addition. However, because these reactions need heating, the funnel neck must be placed on the reaction liquid, so a separatory funnel is used.

nine

Storage and use of special reagents

1, Na, k: isolated from air; Anti-oxidation, stored in kerosene (or liquid paraffin), (plum sealed with paraffin). Take it off with tweezers, cut the glass slide, suck the kerosene with filter paper, and then put the rest in the kerosene.

2, white phosphorus: stored in water, antioxidant, cold and light. Tweezers, and immediately put it in water, cut with a long-handled knife. Filter paper absorbs moisture.

3. Liquid Br2: toxic, volatile, put in a ground-mouth flask and sealed with water. The bottle cap is tight. 4.I2: It is easy to sublimate and has a strong pungent smell. It should be kept in a bottle sealed with wax and kept at low temperature.

5, concentrated nitric acid, silver nitrate: easy to decompose when exposed to light, should be stored in a brown bottle, and placed in a low temperature and dark place.

6. Solid alkali: it is easy to deliquesce and should be stored in a dry flask that is easy to seal. The bottle mouth is plugged with a rubber stopper or covered with a plastic cover.

7.NH3H2O: volatile, sealed at low temperature.

8.C6H6, C6H5-CH3, CH3CH2OH, CH3CH2OCH2CH3: volatile, flammable, and should be stored in a closed place at low temperature, away from fire sources.

9.Fe2+ salt solution, H2SO4 33 and its salt solution, hydrogen sulfate and its salt solution: It is not suitable for long-term storage because it is easy to be oxidized by air, so it should be prepared now.

10, salt water, lime water, silver ammonia solution, Cu(OH)2 suspension, etc. , you should take it with you, not leave it for a long time.

ten

Chemistry and "0" and decimal point

1, and the scale at the top of burette is 0. There are two decimal places.

2. The scale at the bottom of the measuring cylinder is 0. The decimal point is one place.

The middle scale of thermometer is 0 degrees. The decimal point is one place.

4. The median value of the pallet scale is 0. The decimal point is one place.

eleven

Gases that can be used in fountain experiments

NH3, HCl, HBr, HI and other water-soluble gases can be used in fountain experiments. If other gases are easily soluble in liquid (such as CO2 is easily soluble in caustic soda solution), fountain experiments can also be done.

twelve

Main experimental operations and experimental phenomena

1. Magnesium rod burns in air: it gives off dazzling light and a lot of heat, and at the same time produces white smoke and a kind of white material.

Charcoal burns in oxygen: it gives off white light and gives off heat.

3. Sulfur burns in oxygen: it releases bright blue-purple flame, releases heat, and produces gas with pungent smell.

4. Iron wire burns in oxygen: it burns violently, sparks are everywhere, heat is released, and black solid substances are produced.

5. Heating ammonium bicarbonate in the test tube: gas with pungent smell is generated, and liquid drops are generated on the test tube. 6. Hydrogen burns in the air: the flame is light blue.

7. Hydrogen burns in chlorine: it gives off a pale flame and generates a lot of heat.

8. Reducing copper oxide with hydrogen in the test tube: black copper oxide turns into red substance, and liquid drops are produced at the mouth of the test tube.

9. charcoal powder is used to reduce copper oxide powder, so that the generated gas is introduced into clear limewater, black copper oxide becomes shiny metal particles, and limewater becomes turbid.

10. Carbon monoxide burns in the air: it gives off a blue flame and gives off heat.

1 1. Dropping hydrochloric acid into a test tube containing a small amount of potassium carbonate solid: generating gas.

12. Heat the copper sulfate crystal in the test tube: the blue crystal gradually turns into white powder, and liquid drops are produced at the mouth of the test tube.

13. Sodium burns in chlorine: violent combustion produces white solid.

14. ignite pure chlorine and cover the flame with a dry and cold beaker: a light blue flame is emitted, and droplets are generated on the inner wall of the beaker.

15. the solution of silver nitrate acidified by nitric acid was dropped into the solution containing C 1- to produce white precipitate.

16. Drop barium chloride solution acidified with nitric acid into the solution containing SO42- to produce white precipitate.

17. Put a rusty nail into a test tube filled with dilute sulfuric acid and heat it: the rust gradually dissolves, the solution turns pale yellow, and gas is generated.

18. Dropping sodium hydroxide solution into copper sulfate solution: blue flocculent precipitate is generated.

19, Cl2 was introduced into colorless KI solution, and brown substance was produced in the solution.

20. Drop the sodium hydroxide solution into the ferric chloride solution: a reddish-brown precipitate is formed.

2 1. Add a small amount of water to the test tube filled with quicklime: the reaction is intense and a lot of heat is released.

22. Immerse clean nails in copper sulfate solution: red substances are attached to the nail surface, and the color of the solution gradually becomes lighter.

23. Insert the copper sheet into the mercury nitrate solution: silver and white material are attached to the surface of the copper sheet.

24. Inject concentrated sodium carbonate solution into a test tube filled with lime water: white precipitate is produced. 25. After the thin copper wire is burned in chlorine, add water: brown smoke is generated, and green solution is generated after adding water.

26. Strong light irradiates the mixed gas of hydrogen and chlorine: the reaction is rapid and an explosion occurs.

27. Red phosphorus burns in chlorine: white smoke is produced.

28. Chlorine gas meets wet colored cloth strips: the color of colored cloth strips recedes.

29. Heat the mixture of concentrated hydrochloric acid and manganese dioxide: produce yellow-green pungent odor gas. 30. Heat the mixture of sodium chloride (solid) and sulfuric acid (concentrated): foggy and pungent.

3 1. Drop silver nitrate solution into sodium bromide solution, and then add dilute nitric acid: pale yellow precipitate is formed.

32. Drop silver nitrate solution into potassium iodide solution, and then add dilute nitric acid: yellow precipitate is formed. 33.I2 meets starch to form a blue solution.

34. Thin copper wire burns in sulfur vapor: when thin copper wire turns red, black matter is produced.

35. Iron powder and sulfur powder are mixed and heated to red heat: the reaction continues, releasing a lot of heat and generating black substances.

36. Incomplete combustion of hydrogen sulfide gas (cover the evaporating dish on the flame): the flame is light blue (there is yellow powder at the bottom of the evaporating dish).

37. Hydrogen sulfide gas burns completely (cover a dry and cold beaker on the flame): the flame is light blue, and gas with pungent smell is generated (droplets are generated on the inner wall of the beaker).

38. Mix hydrogen sulfide and sulfur dioxide in a gas container: yellow powder is generated on the inner wall of the bottle.

39. Introduce sulfur dioxide gas into magenta solution, and then heat it: the red color recedes, and the original color is restored after heating.

40. Put excess copper into a test tube filled with concentrated sulfuric acid and heat it. After the reaction, water was added to the solution after cooling: gas with pungent smell was generated, and the solution was sky blue after adding water.

4 1. Heat the test tube filled with concentrated sulfuric acid and charcoal: generate gas, which has a pungent smell.

42. Sodium burns in the air: the flame is yellow, producing light yellow substances.

43, sodium into the water: the reaction is fierce, sodium floats on the water surface, releasing a lot of heat to make sodium dissolve into small balls swimming on the water surface, with a "before" sound.

44. Drop water into a test tube filled with sodium peroxide solid, and put the wooden strip with Mars into the mouth of the test tube: the wooden strip is re-ignited.

45. Heat the sodium bicarbonate solid to make the generated gas flow into the clarified limewater: the clarified limewater becomes turbid.

46. Ammonia meets hydrogen chloride: there is a lot of white smoke.

47. Heat the mixture of ammonium chloride and calcium hydroxide: produce a gas with pungent smell.

48. Heat the test tube filled with solid ammonium chloride: white crystals are produced at the mouth of the test tube.

49. The concentrated nitric acid in colorless reagent bottle is exposed to the sun: the space in the bottle is brown and the nitric acid is yellow.

50. Reaction between copper sheet and concentrated nitric acid: The reaction is fierce, producing reddish-brown gas.

5 1. The copper sheet reacts with dilute nitric acid: colorless gas is produced at the lower end of the test tube, which gradually turns reddish brown when it rises.

52. Adding dilute hydrochloric acid to sodium silicate solution will produce white colloidal precipitation.

53. Add magnesium sulfate solution to the iron hydroxide colloid: the colloid becomes turbid.

54. Heat the iron hydroxide colloid: the colloid becomes turbid.

55. Put the ignited magnesium rod into a gas container filled with carbon dioxide: it burns violently, and black substances are attached to the inner wall of the gas container.

56. Dropping ammonia water into the aluminum sulfate solution: fluffy white flocculent substances are generated.

57. Drop the sodium hydroxide solution into the ferrous sulfate solution: form a white flocculent precipitate, which immediately turns gray-green and then red-brown precipitate.

58. Drop the KSCN solution into the solution containing Fe3+: the solution is blood red.

59. Add chlorine water dropwise to the sodium sulfide aqueous solution: the solution becomes turbid. S2-+Cl2=2Cl2-+S↓

60. Add a small amount of soap to natural water: the foam gradually decreases and precipitation occurs.

6 1, ignite the methane in the air, and put the dry and cold beaker on the flame: the flame is light blue, and droplets are produced on the inner wall of the beaker.

62. Irradiate the mixed gas of methane and chlorine: the yellow-green color gradually becomes shallow for a long time (droplets are generated on the inner wall of the container).

63. Heat the mixture of ethanol and concentrated sulfuric acid (170℃), and introduce the generated gas into bromine water and acidic potassium permanganate solution: when the gas is generated, the bromine water fades and the purple gradually becomes lighter.

64. Ignite the ethylene in the air: the flame is bright, producing black smoke and releasing heat.

65. Ignite acetylene in the air: the flame is bright, producing smoke and releasing heat.

66. Benzene burns in air: the flame is bright and there is black smoke.

67. Ethanol burns in the air: the flame is light blue.

68. Introduce acetylene into bromine water: bromine water fades.

69. Introduce acetylene into acidic potassium permanganate solution: purple gradually becomes lighter until it fades.

70. Benzene reacts with bromine in the presence of iron powder as catalyst: white mist is produced and the product is oily brown.

7 1. Pour a small amount of toluene into a proper amount of potassium permanganate solution and shake well: purple fades.

72. Put sodium metal into a test tube filled with ethanol: the gas is released.

73. Drop excessive concentrated bromine water into a test tube containing a small amount of phenol: form a white precipitate.

74. Drop a few drops of ferric chloride solution into a test tube containing phenol and shake well: the solution turns purple.

75. Acetaldehyde reacts with silver ammonia solution in the test tube: the inner wall of the clean test tube is attached with a layer of bright as a mirror.

76. When heated to boiling, acetaldehyde reacts with newly formed copper hydroxide: a red precipitate is formed.

77. Under suitable conditions, ethanol reacts with acetic acid to produce a transparent oily liquid with fragrance.

78. protein encountered a concentrated nitric acid solution: it turned yellow.

79. Purple litmus test solution turns blue when it meets alkali.

80. Colorless phenolphthalein test solution turns red when it meets alkali.

thirteen

Wonderful use of water in experiment

1, water seal: In the middle school chemistry experiment, liquid bromine needs water seal, and a small amount of white phosphorus is stored in a jar filled with cold water. Covering with water can not only isolate the air to prevent the white phosphorus vapor from escaping, but also keep it below the ignition point; Liquid bromine is highly volatile and toxic. It is insoluble in water and heavier than water, so it can also be sealed with water to reduce its volatilization.

2. Water bath: preparation of phenolic resin (boiling water bath); The preparation of nitrobenzene (50-60℃), the hydrolysis of ethyl acetate (70-80℃), the hydrolysis of sucrose (70-80℃) and the determination of potassium nitrate solubility (room temperature-100℃) need thermometer control. Silver mirror reaction needs warm water bath heating.

3. Water collection: Water-insoluble or water-insoluble gases, including O2, H2, C2H4, C2H2, CH4 and NO, can be collected by drainage gas collection method. Some gases have certain solubility in water, but they can be reduced by adding some substances to the water, such as collecting chlorine by discharging saturated brine.

4. Water washing: Soluble impurities in some insoluble gases can be removed by water washing, such as removing NO2 impurities in NO gas.

5. Identification: Some substances can be identified by their solubility or density in water. For example, three bottles of unlabeled colorless liquid, benzene floating in water, ethanol dissolved in water and bromoethane submerged in water can all be used for identification. Identification by heat of solution, such as sodium hydroxide, ammonium nitrate, sodium chloride and calcium carbonate, can only be identified by water.

6. Leak detection: After the gas generator is connected, the principle of thermal expansion and cold contraction can be applied to check whether there is water leakage.

fourteen

The phenomenon is different when the dropping order is different.

1, AgNO3 and NH3H2O:AgNO3 drops into NH3H2O-there is no white precipitate at first, and then a white precipitate is generated. NH3H2O dripped into AgNO3-white precipitate appeared at first, and then disappeared.

2.NaOH and AlCl3: When NaOH is dropped into AlCl3, white precipitate begins to appear and then disappears. Drop AlCl3 into NaOH-no white precipitate appears at first, and then white precipitate appears.

3.HCl and NaAlO2: When HCl is dropped into NALO2, white precipitate begins to appear and then disappears. NALO2 was added dropwise to HCl-there was no white precipitate at first, and then white precipitate appeared.

4.Na2CO3 and hydrochloric acid: Na2CO3 drops into hydrochloric acid-bubbles appear at first, but no bubbles are generated later; Hydrochloric acid drops into Na2CO3-there is no bubble at first, and then bubbles are generated.

Answering skills of chemistry experiment questions in college entrance examination

1, which is the soul of the experiment according to the experimental principle or purpose; Only by fully understanding the experimental principle or purpose and combining the functions of the device given in the question can the connection problem of experimental instruments be solved smoothly; Only by fully understanding the experimental principle can we answer the function or experimental phenomenon of the device with the reagents in the device.

2. Read the questions repeatedly and extract effective information. Don't expect to read the questions once and answer them smoothly. Sometimes the answer lies in the information of the question. Through repeated reading, we can find the connection between the answer to the question and the known information.

3, good at association, before and after contact, whether it is the same type of problem that I have done before, or the same problem-solving ideas, let the wings of thinking fly freely and avoid unopened and rigid thinking.

4. Experimental questions are a window to examine language expression ability. When answering the experimental phenomenon or the function of each step, we should be comprehensive, accurate and standardized to avoid being vague and taking it lightly.

How to learn high school chemistry well?

1 It's best to preview before class 10 minutes, so calm down and think about it.

question

Listening carefully is the key. Turn the textbook materials to what the teacher said in class.

Take notes on important knowledge points. Review after school, and communicate with teachers or classmates in time if you don't understand.

We should cultivate our hands-on ability in the experimental class and verify the contents of the class with experiments.

When no one can ask, you can go to Baidu to search for questions.

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