The most complete operation taboos and tips for the experiment
1. The straw must not be sucked by the mouth. Some people say: "I know this is water!" Despite this, do you know the content and cleanliness of these waters? Do you know the cleanliness of the containers that store these waters? Even at home You can't do this casually. Some people like to use their mouths to suck kerosene or gasoline. (Really trying to do experiments! It ’s horrible!)
2. Smell the gas and flutter into the nose. Don't look at a small operation. I once heard that someone entered the hospital because of a sip of Cl2.
3. Eating and drinking are prohibited in the laboratory. Some people once drank the reagents next to them while eating while looking at the microscope. Despite the urgency of gastric lavage, it is inevitable to be disabled, and the use of laboratory reagents as food And additives ", such as: NaCl or distilled water. Because, you do n’t know the purity and impurities in NaCl, the same is true for distilled water, remember!
4. Brush the bottle, be sure to brush inside and out, to save you time later to find out whether the dirty thing is inside or outside.
5. The laboratory cannot wear leather shoes with iron palms nailed because it will rub against electricity.
6. When there are many samples or some samples still need to be used later, be sure to put a label, even if you have a good memory, you must post it, otherwise, if you forget, you may spend several times to think that it is ?
7. After any experiment fails, don't rush to mess up the reactants, maybe, after some time you wake up, you will regret the impulse just now.
8. To do experiments, be sure to record the data truthfully. Any random messing or even tampering with the data will cause you trouble.
9. It is better to wear a glass lens for the experiment to prevent the solvent and corrosive substances from splashing into the eyes. The resin lens is more likely to be corroded.
10. Always keep your experiment table clean, not only for you to get good results, but also for your own mood.
11. Be sure to think about what you are doing before the experiment. Doing a good job of experiment preparation is by no means an empty talk, otherwise the cluttered thoughts are easy to make mistakes and accidents.
12. Fatigue operation is strictly prohibited.
13. The heating test tube must not be heated centrally, and the test tube mouth should not be aimed at people, to prevent the liquid from overheating and flushing.
14. It is strictly forbidden for all organic solvents to be heated directly in the flask, which is the most dangerous. If the solvent is exposed or the bottom of the bottle is broken, the operator next to it is very dangerous.
15. Pay attention to exhaust ventilation when using high-risk solvents such as chloroform, carbon tetrachloride, methanol and benzene, or strong irritant gases such as hydrochloric acid.
16. It is forbidden to use alkaline substances in the acid burette, otherwise it will corrode the frosted glass part and the wall of the pipe, causing leaks and inaccurate volume; the alkali burette is strictly prohibited from using strong oxidizing agents, such as potassium permanganate potassium dichromate, If it is a neutral substance, try to use a basic burette (basic burette is easy to operate).
17. Sulfuric acid, nitric acid and other oxidizing acids, pay attention to the safety of use. If you accidentally drop it on your body, use water to wash it, and then wash it with sodium bicarbonate solution. Do not ignore it because the concentration is very low, because, as the water evaporates The concentration of sulfuric acid will increase, and the original washed sulfuric acid will also become concentrated sulfuric acid.
18. Vacuum distillation is a very dangerous operation. Remember, during vacuum distillation, people must not approach the reaction device, and must wear protective equipment, such as goggles, because vacuum distillation depends on the quality of the equipment, glass container The small flaws will be pressed by the external atmospheric pressure during decompression. If there is a crack, it will cause the entire glassware to burst and hurt the experimenters.
19. Don't forget to add zeolite when performing any solvent reflux operation (of course, if you have solid powder raw materials, you can use it as zeolite) .If you forget to add zeolite during the reaction, it is also prohibited to add it when the liquid is hot! Otherwise, add it Zeolite will stimulate the liquid's own overheating energy, causing the liquid to flush. The maximum can reach a few meters. The overheated solvent will be sprayed everywhere. If it is a toxic solvent, it is unbearable.
20. All organic waste liquid must be put into the waste liquid tank, and it is forbidden to pour into the sewer, causing environmental pollution. All high-concentration inorganic waste liquids, including acids and bases, and all toxic waste liquids, such as arsenic reagents, are strictly prohibited from being poured into the sewer.
21. All the operations of the experiment must first learn the teacher's standards, and then carry out their own operations. It is often seen that some students do not even know how to take the burette, and how to add the burette (especially the alkaline burette).
22. When conducting experiments with ether, pay attention to exhaust and fire prevention.
All the operations of the experiment are actually accumulated over time. Do not think that the experiment is unimportant. On the contrary, the experiment is sometimes more important than the theory. Although the middle school experiment may not be able to help you enter the university, the experiment cannot be ignored in the knowledge system of chemistry. A very simple operation such as the end point titration of acid-base titration, the grasp of 1/2 and 1/4 drops, can often see the basic quality of a person's chemistry. If you are devoted to the chemical business, the basic chemical operations are also items that need to be evaluated, including: configuring standard concentration solutions that we have learned in high school.
Tips to be mastered in college chemistry experiments
1. When washing the NMR sample tube, be sure not to drop the water inside the pool; when removing the cap of the sample tube, hold the tube in one hand and the cap in one hand, and do not pull the hero in one hand (NMR sample tube is not cheap).
2. Rotary steamer must use a round bottom flask, otherwise the low pressure is easy to penetrate the flask.
3. Obtain new test data, even if it is ideal, do not immediately open champagne to celebrate, while he is still sober, and immediately carry out data processing.
4. Preservation of the reference mother liquor. Sometimes the reference is more precious to us than gold, otherwise you never know whether you have succeeded. Therefore, after the reference mother liquor is used up, it must be sealed with a parafilm and placed in the refrigerator for storage.
5. The volumetric flask should be washed carefully. If ultrasound is not used, soak it in the lotion for a while.
6. Don't think that the automatic sampling of HPLC can make you not look at it. Sometimes the instrument malfunctions and the column pressure will be higher than 30KPa.
7. The column must be tripped with the solvent first, otherwise the silica gel or resin will expand and the column will be destroyed.
8. Volatile solvents should never be placed in the refrigerator, otherwise they will become bombs.
9. Don't always believe in purchased reagents, especially domestic ones. When you are puzzled, it may be the inferior reagents that make you depressed.
10. Label your own reagents, or you will be too late to cry when others throw your important products around.
11. When turning off steaming, be sure to pull out the vacuum first, then turn off the pump, otherwise wait for the pumping.
12. Keep the bottle in the refrigerator, and be careful not to put the stopper too tight or you will be too busy.
13. Put on the latex tube. If you are right-handed, be sure to hold the tube in your right hand and the glass in your left hand, otherwise you will get injured in the hand sooner or later.
14. For closed system experiments, balloons must be installed, otherwise. . .
15. After putting the volatile material in the open bottle, it should be sealed with a film after use. How carefully, it is also for your own life.
16. Pipette guns must not be used for volatile organic solvents, especially imported eppendorf or gelson guns. After the aerosol corrodes the gun head, this gun will be used up.
17. Alcohol blowtorch must not be poured too much, otherwise the slope will be large, and the consequences will be serious if you spill the alcohol.
18. Use the funnel to add liquid solvent, be sure not to add too much at a time, leaving a bit for later washing the funnel.
Several poems for reference:
The operation of the experiment:
Solids need spoons or paper slots, stick labels by hand and dump. The reading should be level with the cut surface, looking up low and looking high.
The dipstick test solution is cut first, and the glass rod dip solution is the best. The test paper is moistened first, and sticks to the stick to lean against the gas.
Wine lamps are heated by external combustion, with two thirds as the limit. Sulfuric acid keeps stirring in the water, and slowly inject to prevent boiling and splashing.
The experiment first checks the air tightness, heating the cup and bottle through the net. After the drainage and gas collection is completed, first remove the catheter and then move the lamp.
Explanation:
1. Solid need spoon or paper slot:
It means that when filling the test tube with solids, in order to avoid the drug from getting on the mouth of the tube and the wall of the test tube, the test tube can be tilted, and the spoon containing the drug (or the paper slot folded with a small paper strip) is carefully Feed into the bottom of the test tube, and then let the test tube stand upright, let the medicine slide down to the bottom.
2. Put the label by hand and then dump:
This means that when taking liquid medicines, the label on the bottle should be attached to the palm of the hand and then dumped (to prevent the liquid remaining on the bottle mouth from flowing down and corroding the label after the medicine is poured).
3. The reading should be flat with the cut surface:
Looking up low and looking high: This sentence means that when taking a certain amount of liquid, you can use a graduated cylinder or a pipette (sometimes, you can also use a burette). When reading, you should make the line of sight scale and the tangent of the lowest point of the liquid concave surface be On the same plane. Otherwise, if you look up, the result is lower, and when you look down, the result is higher.
4. Cut the test strip to measure the liquid first.
"Glass rod" refers to a glass rod. This means that when testing the properties of the solution with test paper, it is best to cut the test paper into a small piece and place it on a watch glass or a glass slide. Use a glass rod with the liquid to be tested to point the middle of the test paper, and the test paper will be wet. Observe whether the color is changed, so that the nature of the solution can be judged.
Use of tray balance:
Screw travel scale, pointer scale has a tray. The adjustment screws are balanced, and the object codes are separated on the left and right sides.
Use tweezers to pick the code, and then remember the heart first. The medicine cannot be put directly, and it should be restored after weighing.
Explanation:
1. Screw travel code scale, pointer scale has a tray:
These two sentences describe the main components that make up the balance of the pallet: (adjusting the zero point) screws, sliders, scales, pointers, and pallets (left and right).
2. The adjustment screw reaches balance: it means that the balance should be checked first before weighing. If it is unbalanced, adjust the screws to make them balanced.
3. The object codes are separated on the left and right sides: "Object" refers to the substance being weighed; "Code" refers to the weight of the balance.
This means: the object to be weighed should be placed in the left tray, and the weight should be placed in the right tray.
4. To take the code, you need to use tweezers: this sentence means that when taking the weight, you must not take it by hand, but you must use tweezers.
5. Bigger first and lesser mind: It means that when adding weights, you should clamp the weights with large masses first, and then clamp the weights with small masses (finally move the moving code).
6. Drugs cannot be placed directly: it means that the weighed drugs cannot be placed directly on the tray (Lenovo: you can put a piece of paper of the same size on each of the two trays, and then put the weighed drugs on the paper Tablets, wet or corrosive drugs must be weighed in a watch glass or beaker).
7. To be restored after weighing: It means that after weighing, the weight should be put back in the weight box, and the moving code should be moved back to zero to restore the balance to its original state.
Filtration experiment:
The glass rod of the beaker is the same as the funnel angle of the filter paper. Let stand before filtering, don't forget to rely on two lows.
Explanation:
(1) The glass rod of the beaker and the filter funnel angle are the same:
"Bucket" refers to a funnel; "rack" refers to a funnel. These two sentences explain the instruments required for the filtration operation experiment: funnel, funnel holder, beaker, glass rod, filter paper, and emphasize that the angle of the filter paper folding should be the same as the angle of the funnel (so that the filter paper can be attached to the funnel wall).
(2) Set aside before filtering:
This means that the liquid must be allowed to stand for a while before filtering to fully separate the solid and liquid.
(3) Don't forget to rely on three lows and two lows:
This means that when filtering, do n’t forget to rely on three-by-two.
"Three lean" means that the end of the funnel neck should lean against the wall of the beaker that receives the filtrate, the glass rod should be leaned against the filter paper, and the mouth of the beaker holding the filter fluid should lean against the glass rod;
"Two lows" means that the edge of the filter paper should be slightly lower than the edge of the funnel, and the liquid level of the poured filtrate should be slightly lower than the edge of the filter paper.
Distillation operation experiment:
The heating tube of the screen is tilted, and the upper edge and the lower edge are flat. It is necessary to add broken porcelain to prevent bumping, and the hot air and cold water go backwards.
Explanation:
1. Separate heating and cooling tube tilting:
"Cold pipe" this condensate pipe.
This means that:
When heating the distillation flask, the asbestos mesh should be separated (to prevent the distillation flask from being broken due to uneven heating), and it should be inclined downward when installing the condenser.
2. The upper and lower edges are even:
It means that the upper edge of the mercury ball of the thermometer should be on the same horizontal line as the lower edge of the interface of the branch pipe of the decanter.
Extraction operation experiment:
The extracts are insoluble in each other, and the degree of solute is different; shake well and let stand, put it down and cut clearly.
Explanation:
1. The extracts are insoluble in each other and the degree of solute is different:
"Extractant" means extractant; "Quality" means solute. The meaning of these two sentences is that in the extraction operation experiment, the principle of selecting the extractant is: the solvent in the extractant and the solution must not be miscible with each other, and the solubility of the solute in the extractant and the original solvent must be different (in the extractant The solubility in is greater than the solubility in the original solution).
2. Fully oscillate and let stand:
This means that during the extraction process, it should be sufficiently shaken to make the extraction sufficient, and then allowed to stand to separate the solution.
3. Put down and cut upside down:
The meaning of this sentence is that the lower liquid of the separating funnel is discharged from the foot of the funnel, and the upper liquid is poured out from the mouth of the funnel.
Neutralization titration
The water washer was clearly divided, and the leak was hurried and then adjusted to zero. Add reagent to the liquid to be tested, left hand control right hand.
The paper under the bottle is eye-sighted, the reading should be flat with the cut surface, the phenolphthalein indicator is familiar, and the strong acid and weak base methyl orange.
Use an acid burette to keep clear of the lye.
Explanation:
1. The water washer is clear:
"Water" has two meanings here, both tap water and distilled water; "liquid" also has two meanings here, both standard solution and liquid to be tested. This sentence means that when doing the neutralization and titration experiments, you must first clean the various instruments, and when you use tap water, when to use distilled water, when to use standard solution, when to use the test solution must be clearly distinguished .
Lenovo: The burette is washed with tap water, distilled water, and standard solution in sequence; the pipette is washed with tap water, distilled water, and the liquid to be tested in sequence; the Erlenmeyer flask is first washed with tap water and then with distilled water, and must not be washed with the liquid to be tested!
2. Check the leak and rush to zero again:
This means that before titration, you should first check whether the burette is leaking, then check whether there is air bubbles at the lower end of the burette, if there is any, you should remove it, and finally adjust the liquid level to the "0" position.
Lenovo:
â‘ The method of leak detection is to add a small amount of standard solution to the washed burette. In case of liquid leakage, apply an appropriate amount of petroleum jelly to the piston for the acid burette, and replace the glass ball for the alkaline burette;
â‘¡Bubble must be removed, because if there is a bubble in the tip of the burette that is not removed, the bubble disappears after the titration, so the measurement result is high;
â‘¢ It is better to start from zero position for each titration, which can reduce the error.
3. Add reagent to the test solution:
"Indicator" means an indicator. This means that before the titration, 2-3 drops of indicator should be added to the Erlenmeyer flask containing the test solution (its role is to indicate the end of the reaction by its color change).
4. Left hand control right hand: It means that during the titration, the burette must be controlled with the left hand, and the conical flask is shaken continuously with the right hand.
5. Under-bottle paper eye-look: "Under-bottle paper" means that in order to clearly observe the color change, you can put a piece of white paper under the bottom of the conical bottle; "Eye-look" means During the titration, you must keep an eye on the color change of the solution, and do not look at the scale of the burette.
6. The reading should be level with the cut surface: for explanation, see "Basic Operation of Chemical Experiments".
7. Phenolphthalein indicator is commonly known, strong acid and weak base methyl orange: this sentence means that neutralizing titration commonly used phenolphthalein as an indicator, only strong acid titration of weak base (such as hydrochloric acid titration of ammonia), you can use methyl orange.
8. Use an acid burette, do not hold lye. Remember: This sentence means that the acid burette cannot be used to hold the alkaline solution (because the lye and SiO2 in the glass react to form Na2SiO3 and the piston and burette stick together) .
Aldehyde oxidation experiment
The amount of ammonia water should be clean in the test tube, and the silver mirror should be heated in the water bath. The liquid dilute alkali usually heats up slowly, and the red precipitates in the liquid.
Explanation:
1. The amount of ammonia water should be test tube clean, and the silver mirror is heated in the water bath:
The meaning of this sentence is to explain the problems that should be paid attention to in the experiment of silver mirror reaction. "The appropriate amount of ammonia water" means that when preparing the silver ammonia solution, the ammonia water should not be excessive, and the precipitation should be dissolved; the "test tube net" means that the test tube for the silver mirror reaction must be clean, otherwise it will not be produced For silver mirrors, only black flocculent precipitates appear. For this purpose, the test tubes must be boiled with 10% sodium hydroxide solution, and then washed with tap water and distilled water in sequence; "warm water bath" means to make silver mirrors The reaction test tube must be warmed in a water bath, and must not be directly heated on an alcohol lamp.
[Lenovo: Nitric acid can be used to remove the silver mirror on the test tube, so that both the silver mirror can be removed and the silver can be recovered. ].
2. The liquid dilute alkali is heated more slowly, and the red precipitation in the liquid is like:
These two sentences explain the problems that should be paid attention to in the experiment of oxidizing aldehyde with newly prepared copper hydroxide. "Liquid dilute" means that the copper sulfate solution, sodium hydroxide solution, and acetaldehyde solution used must be dilute; "Alkali more" means that the alkali (sodium hydroxide) in the experiment should be excessive, and the sulfuric acid used The amount of copper must be small. Otherwise, you will not get a red precipitate, but a dark brown precipitate. This is because a large amount of copper sulfate generates a large amount of copper hydroxide. The excessive copper hydroxide will be decomposed by heat to form black copper oxide, and the mixed color of black copper oxide and red cuprous oxide is dark brown.
Important demonstration experiment
Pale flame of hydrogen in chlorine, smog of phosphorus in chlorine; methane, hydrogen and chlorine are mixed, and strong light exposure is too dangerous;
The magnesium in carbon dioxide burns, and the two acids meet with ammonia to emit white smoke; the ammonium chloride heat sublimes, and the iodine turns blue when it encounters starch;
Sulphurethane-oxygen carbon, the five burning flame blue; copper wire extends into the sulfur gas, sulfur and iron mixed with black creatures;
The hot copper and hot iron meet chlorine gas, and the smoke color is brown.
Explanation:
1. Pale flame of hydrogen in chlorine: It means that the flame of hydrogen burning in chlorine gas is pale (a lot of acid mist is generated at the mouth of the bottle).
2. Phosphorus smoke diffuses in chlorine: It means that phosphorus burns in chlorine gas to produce white smoke. White smoke is a mixture of the resulting colorless liquid phosphorus trichloride and white solid phosphorus pentachloride.
3. Methane, hydrogen and chlorine are mixed, and the strong light exposure is too dangerous: these two sentences mean that methane and chlorine mixed or hydrogen and chlorine mixed will explode under the strong light.
4. Magnesium bar burning in carbon dioxide: "Dioxygen carbon" refers to carbon dioxide: meaning that magnesium bar can be burned in carbon dioxide. Put the ignited magnesium bar into the gas cylinder containing carbon dioxide. The magnesium bar burns violently to produce white magnesium oxide powder. At the same time, the precipitated carbon black adheres to the inner wall of the gas cylinder. The reaction formula is: 2Mg + CO2 = 2MgO + C .
5. The two acids meet with ammonia and emit white smoke: "two acids" refers to concentrated hydrochloric acid and concentrated nitric acid. This means that when concentrated hydrochloric acid and concentrated nitric acid meet ammonia, white smoke will be produced. This white smoke is a tiny ammonium chloride (ammonium nitrate) crystal formed by the combination of ammonia and hydrogen chloride (nitric acid) volatilized from concentrated hydrochloric acid (concentrated nitric acid). The reaction formula is: NH3 + HCI = NH4CI, NH3 + HNO3 = NH4NO3.
6. Sublimation of the thermal image of ammonium chloride: it means that ammonium chloride crystals are heated in a test tube, then ammonium chloride is decomposed into ammonia and hydrogen chloride gas, and then recombined to form ammonium chloride solid when the nozzle is cooled Like sublimation, but it is not sublimation in nature. Because sublimation is a physical change, what happens during the decomposition and crystallization of ammonium chloride is a chemical change.
7. Iodine turns blue when it meets starch: It means that iodine turns blue when it encounters starch. This property is often used to identify trace amounts of iodine or starch.
8. Sulphur methane and carbon monoxide, the five burning flame blue:
"Sulfur and hydrogen" has three meanings here: refers to sulfur, hydrogen and hydrogen sulfide; "carbon monoxide" refers to carbon monoxide. This sentence means that the five substances of sulfur, hydrogen, hydrogen sulfide, methane, and carbon monoxide all produce a light blue flame when they burn.
Lenovo: Identification of hydrogen, methane and carbon monoxide. Although they are all colorless gases and the lighted flames are light blue, they can be distinguished according to different chemical properties. The method is to cover a beaker above the flame, and then turn the beaker upside down to add clear lime water. It is hydrogen that produces water droplets but does not make the lime water turbid; not only water droplets are produced, but it is methane that can make the clear lime water turbid; without water generation, it is carbon monoxide that makes the lime water turbid; no water The formation of beads cannot make the lime water turbid, and the generated gas has a pungent odor of hydrogen sulfide. .
9. The copper wire extends into the sulfur gas, and the sulfur and iron are mixed with black matter. This sentence means that the copper wire is extended into the hot sulfur vapor, and the sulfur powder and iron powder are mixed and heated to react to form a black substance (Cu2S And FeS).
10. The hot copper and hot iron meet the chlorine gas, and the smoke color is brown: the two sentences mean that a bunch of hot copper wire and iron wire are put into the gas cylinder containing chlorine gas, and the red hot copper can be seen The wire or iron wire burns in the chlorine gas, and the gas cylinder is filled with brown smoke, which is crystal particles of copper chloride or iron chloride.
Lenovo: Distilled water is added after the gas cylinder cools. The green solution produces copper chloride, and the brown solution produces ferric chloride.
Halogen elements and their compounds
Chlorine gas is toxic and irritating, smelling chlorine gently fanning with hands.
The hot copper and hot iron meet chlorine gas, and the smoke color is brown.
Hydrogen pales in flames in chlorine and phosphorus diffuses in chlorine.
Methane, hydrogen and chlorine are mixed, and strong light exposure is too dangerous.
Chlorine disinfection and bleaching, hypochlorous acid.
Slaked lime chlorine bleach, often used carbon dioxide,
When manganese dioxide hydrochloric acid is used, chlorine gas is generated in a hot bottle.
Salt water sulfuric acid removes impurities and absorbs into caustic soda.
The sulfuric acid salt bottle heats up, and the funnel absorbs hydrogen chloride.
Industrial electrolytic salt water, chemical synthesis of Yin and Yang products.
The flask is dry and airtight, and the gas is full.
Squeeze the plastic head quickly, the red fountain is enchanting.
Four elements of chlorofluoro, bromine and iodine, the color gradually deepens and the gas becomes solid.
The radius density gradually increases, and the melting point and boiling point also increase.
The fixed iodine can be sublimated by heating, and the bromine iodine in the organic agent can be dissolved.
All four seek water and hydrogen, with varying degrees of conditions.
The upper side can be changed, the iodine will turn blue when it meets starch.
Halogen oxidizes sulfurous acid and replaces sulfur in hydrogen sulfide.
Yingshi Hydrogen Sulfate Sulfate, remember to be in a lead dish.
Hydrobromic acid is really difficult, and phosphoric acid is not used for sulfuric acid.
Chlorobromide and phosphate, plus acid and silver nitrate.
Silver halide light is easy to decompose, and the rain of photography is remembered.
Explanation:
1. Chlorine is toxic and irritating, smelling chlorine gently fanning with your hands: These two sentences mean that chlorine is toxic and irritating (a small amount of chlorine inhalation will irritate the mucous membranes of the nose and throat, causing chest pain and coughing Chlorine gas will be poisoned and die). When smelling chlorine gas, you must be very careful. You should gently fan the mouth of the bottle with your hand to make only a small amount of chlorine gas float into the nostrils.
2. Chlorine water disinfection and bleaching, the principle of action Hypochlorous acid: these two sentences mean that chlorine gas can be dissolved in water (1 volume of water can dissolve about 2 volumes of chlorine gas), the aqueous solution of chlorine gas is called chlorine water, chlorine gas can follow Water reacts chemically to produce hydrochloric acid and hypochlorous acid (CI2 + H2O = HCI + HCIO). Hypochlorous acid is a strong oxidant that can kill germs in water, so tap water often uses chlorine gas (about 0.002 grams in 1 liter of water Chlorine) to sterilize. Hypochlorous acid can fade dyes and organic colors, and can be used as a bleaching agent.
3. Slaked lime chlorine bleaching powder: It means that slaked lime and chlorine gas can be made into bleaching powder (bleaching powder is a mixture of calcium hypochlorite and calcium chloride, its effective component is calcium hypochlorite), the reaction formula is: 2Ca (OH) 2 + 2Cl2 = Ca (ClO) 2 + CaCl2 + 2H2O.
4. Use carbon dioxide often: "carbon dioxide" refers to carbon dioxide, which means that carbon dioxide and water vapor often enter the air when bleached with bleach, the reaction formula is Ca (ClO) 2 + CO2 + H2O = CaCO3 ↓ + 2HClO.
Lenovo: Hypochlorous acid is a weak acid. Stronger acids can replace it from the salt. For example, Ca (ClO) 2 + 2HCl = CaCl2 + 2HClO.
5. Sulfuric acid salt flask heats, the funnel absorbs hydrogen chloride: these two sentences mean that in the laboratory, concentrated sulfuric acid and table salt are heated in a flask to prepare hydrogen chloride. To absorb hydrogen chloride, a funnel must be reversed on the surface of the water, so that the hydrogen chloride can be fully absorbed without reverse absorption.
6. Four elements of fluorochlorobromoiodine, the color gradually deepens, and the gas solidifies: it means that the elemental color of these four elements gradually becomes darker, and the state changes from gaseous to solid (fluorine is yellowish green gas, chlorine is Yellow-green gas, bromine is red-brown liquid, iodine is purple-black solid).
7. The radius density gradually increases, and the melting point and boiling point also increase: This means that the atomic radius, ionic radius, and density of these four elements of these four elements gradually increase, and the melting point and boiling point also gradually increase.
[Lenovo: Substances with similar composition and structure increase in molecular weight, and the intermolecular forces also increase, which is manifested in the increase in melting point and boiling point, such as homologues in organic matter].
8. Fixed iodine can be sublimated by heating: it means that solid iodine can sublimate when heated.
[Lenovo: This characteristic of iodine is often used to separate iodine from other substances].
9. Bromine and iodine in organic agent: It means that bromine and iodine are easily soluble in organic solvents, such as gasoline, benzene, carbon tetrachloride, alcohol, etc.
Lenovo: â‘ The iodine used in medical treatment is an alcohol solution of iodine; â‘¡ Using this property, bromine and iodine can also be extracted from other substances.
10. All four seek water and hydrogen, with varying degrees of conditions:
The meaning of these two sentences is that chlorochlorobromide can react with water and hydrogen, but the required conditions and the degree of reaction vary.
11. You can change the bottom to the top:
It means that among the halogen elements, the ones on the top can replace the ones on the bottom, such as: 2NaCl + F2 = 2NaF, 2NaBr + Cl2 = 2NaCl + Br2, 2NaI + Br2 = 2NaBr + I2.
12. Iodine turns blue when meeting starch:
This means that iodine turns blue when it encounters starch. This property is often used to identify trace amounts of iodine or starch.
13. Halogen oxidizes sulfurous acid and replaces sulfur in hydrogen sulfide:
This means that halogen (X2) can oxidize sulfurous acid to sulfuric acid and can replace sulfur in hydrogen sulfide.
The reaction formula is: H2SO3 + X2 + H2O = H2SO4 + 2HX, H2S + X2 = 2HX + S.
14. Yingshi hydrogen fluoride sulfate, remember to be in a lead dish:
This means that in the laboratory, fluorite and sulfuric acid are reacted in a lead dish to produce hydrogen fluoride. The reaction formula is:
CaF2 + H2SO4 = CaSO4 + 2HF ↑
Lenovo: Glass instruments cannot be used because hydrogen fluoride can corrode glass: 4HF + SiF4 = SiF4 + 2H2O.
15. Hydrobromic acid is really difficult, without phosphoric acid:
This means that when preparing hydrobromic acid and hydroiodic acid, concentrated sulfuric acid cannot be used, but phosphoric acid must be used. The reaction formula is:
NaBr + H3PO4 = HBr ↑ + NaH2PO4;
NaI + H3PO4 = HI ↑ + NaH2PO4
Lenovo: Because concentrated sulfuric acid has strong oxidizing properties, the generated HBr and HI can oxidize Br2 and I2; the reaction formula is: 2HBr + H2SO4 = SO2 ↑ + Br2 + 2H2O, 2HI + H2SO4 = SO2 ↑ + I2 + 2H2O
16. Chlorobromide and phosphate, plus acid and silver nitrate:
"Chlorobromoiodine" refers to CI-, Br-, I- here. The meaning of these two sentences is that the identification method of CI-, Br-, I- and PO43- is to add dilute nitric acid and then silver nitrate. Those with white precipitation are CI-, those with light yellow precipitation are Br-, those with yellow precipitation I-, and those without precipitation are PO43- (this is because PO43- and Ag + can also produce AgI-like Yellow precipitates Ag3PO4, but it can be dissolved in dilute nitric acid).
17. Silver halide light is easy to decompose.
This means that:
Silver halide is easily decomposed when it sees light, so it has two major uses:
One is to make photosensitive materials in the photography industry;
The second is for artificial rainfall.
Nomenclature of alkanes
The longest carbon chain is called a certain alkane, which is close to the branch chain number. Simultaneously in the same phase, a short line should be drawn.
Explanation:
(1) The longest carbon chain is called an alkane: it means that the longest carbon chain in the molecule is selected as the main chain and is called "a certain alkane" according to the number of carbon atoms in the main chain.
(2) Numbering close to the branch chain: meaning that the end of the main chain closer to the branch chain is used as the starting point, using 1, 2, and 3. . . Equal numbers position each carbon atom in the main chain to determine the position of the branch.
(3) Simple and in-phase, and a short line should be drawn in between: these two sentences mean that the branch is used as a substituent, the name of the substituent is written in front of the name of the alkane, and the number of the substituent is indicated by Arabic numerals Its position on the main chain of alkane, and simple substituents should be written in front of complex substituents, if there are the same substituents, they should be combined with two or three numbers, but the same substituent position Arabic numbers should be separated by commas, followed by a dash after the numbers, separated by "-" in the middle.
For example, 2,4-dimethyl-3-ethylheptane, 2-methylbutane;
Ethylene
Three-to-one sulfuric acid ethanol, the temperature is counted into the liquid 170; rapid temperature increase to prevent carbonization, alkali ash removal is most suitable.
The ethylene molecule contains double bonds, and oxidation addition is not difficult; potassium permanganate is purplish red, and halogen hydrogen is hydrogen halogen acid.
Ethylene polymerizes good plastics, and the burning flame emits black smoke brightly; ethylene is hydrated to produce ethanol, which is oxidized to obtain aldehyde and acid.
Explanation:
(1) Ethylene molecules contain double bonds, and oxidation addition is not difficult: these two sentences mean that because ethylene contains double bonds, it is easy to be oxidized and addition reactions can also occur.
(2) Potassium permanganate purplish red: means that ethylene can fade the acidified potassium permanganate solution.
(3) Halogen, hydrogen, and halogen acid: meaning that ethylene can react with halogen, hydrogen, and halogen acid.
(4) Ethylene polymerizes good plastics: It means that ethylene is polymerized to get good plastic polyethylene.
(5) Burning flame produces bright black smoke: It means that ethylene burning flame is bright and produces black smoke.
(6) Hydration of ethylene to produce ethanol: It means that ethylene reacts with water to produce ethanol under certain conditions.
(7) Oxidation yields aldehydes and acids: meaning that ethylene is oxidized to acetaldehyde under the action of a catalyst, and acetaldehyde is further oxidized to obtain acetic acid.
Storage of common chemicals
Nitric acid fixed iodine silver nitrate, brown bottle at low temperature and dark; liquid bromine ammonia is volatile, and should be sealed in cool storage.
White phosphorus storage requires cold water, potassium, sodium, calcium and barium kerosene; alkali bottles need rubber stoppers, plastic lead to store hydrogen fluoride.
The perishable medicines are short-lived, flammable and explosive to avoid fire sources; in the laboratory, the desiccant and the wax seal keep calm.
Explanation:
1. Silver nitrate fixed iodine silver nitrate, low temperature dark brown bottle: means that nitric acid, solid iodine and silver nitrate are all substances that decompose easily when exposed to light, so they must be stored in a brown bottle and placed in a cool place.
2. A rubber stopper is required for the alkali bottle: it means that the reagent bottle for the alkali solution should use a rubber stopper.
3. Plastic lead storage hydrogen fluoride: It means that hydrogen fluoride (hydrofluoric acid) is easy to corrode glass, so it must be stored in plastic or lead utensils.
4. Short-term release of perishable medicines: It means that the storage time of perishable medicines is short, that is, they cannot be stored for a long time.
Lenovo: Commonly perishable medicines are:
â‘ Hydrochloric acid is left for a long time, most of it will be volatilized, and some will be oxidized by air;
â‘¡ Long-term storage of chlorine water will fail due to slow decomposition;
â‘¢ If ferrous salt is stored for a long time, it will be easily oxidized to iron salt;
â‘£The acidified potassium permanganate solution fades slowly after long-term storage.
5. Flammable and explosive fire source:
It means that flammable substances (such as carbon disulfide, alcohol, acetone, benzene, sulfur, phosphorus, magnesium powder, etc.) and explosive substances (such as potassium chlorate, ammonium nitrate, etc.) should be kept away from ignition sources.
6. The desiccant in the laboratory, the wax seal is safe to keep:
It means that the desiccant used in the laboratory is very easy to absorb water, so it should be stored with a wax seal.
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