Knowledge points of high school chemistry competition
Preparation and properties of methane
1. reaction equation CH3COONa+NaOH→ heating-Na2CO3+CH4.
2. Why do you have to use anhydrous sodium acetate?
Moisture jeopardizes this reaction! If there is water, the electrolyte CH3COONa and NaOH will ionize, which will change the breaking position of the bond without generating CH4.
3. Why do you have to use alkali lime instead of pure NaOH solid? What is the function of CaO in soda lime? At high temperature, NaOH solid corrodes glass;
The function of CaO: 1) can dilute the concentration of reaction mixture, reduce the contact between NaOH and test tube, and prevent glass from being corroded. 2) Cao Can absorbs moisture and keeps NaOH dry.
4. Which device is used to produce methane? What is the reason why the large test tube inclines slightly downward in the reaction device? What other gases can this device produce?
A device for heating a slightly downward inclined large test tube is adopted, because it is convenient for the diffusion of solid drugs, and at the same time, it prevents the generated wet stored water from flowing back and breaking the test tube; It can also produce O2, NH3, etc.
5. In the experiment, CH4 gas was first introduced into KMnO4(H+) solution and bromine water, and then ignited. What is the purpose of this operation?
Exhaust the air in the test tube, ensure the purity of methane, and prevent methane from mixing with air and igniting the explosion.
6. Why is the flame slightly yellow when methane is ignited? What color is pure methane ignited?
Effect of sodium in glass; The combustion of acetone vapor, a by-product in the reaction, makes the flame slightly yellow.
2) Light blue when the pure methane flame is ignited.
Preparation and properties of ethylene
1. Chemical equation C2H5OH concentrated H2SO4, 170℃→ CH2=CH2+H2O.
2. Which device is used to prepare ethylene? What other gases can this device produce?
Both the separating funnel and the round bottom flask (heating) are equipped with a set of devices. The device can also produce Cl2, HCl, SO2, etc.
3. What is the purpose of adding a few pieces of broken glass (broken porcelain) to the flask in advance?
Prevent boiling (prevent the mixture from jumping violently when heated)
4. When ethanol and concentrated sulfuric acid are mixed, sometimes ethylene cannot be obtained. What could be the reason?
This is mainly because the temperature did not rise rapidly to 170℃. Because at 140℃, ethanol will undergo intermolecular dehydration to obtain ether, and the equation is as follows:
2C2H5OH-concentrated H2SO4, 140℃→ C2H5OC2H5+H2O
5. What is the position and function of the mercury ball of the thermometer?
Below the liquid level of the mixed liquid; Used to measure the temperature of mixed liquid (control temperature).
6. What is the function of concentrated H2SO4? Catalyst, dehydrating agent.
7. In the later stage of the reaction, the reaction liquid sometimes turns black and produces gas with pungent smell. Why?
The irritating gas produced by the carbonization and oxidation of ethanol with concentrated sulfuric acid is SO2.
C+2H2SO4 (concentration)-heating → CO2+2SO2+2H2O
Preparation and properties of acetylene
1. reaction equation CaC2+2H2O→Ca(OH)2+C2H2
2. Can 2.Kipp generator be used in this experiment? Why?
No. Because 1)CaC2 has strong water absorption and reacts violently with water, it is not easy to control its reaction with water if it is used in a Keppel generator. 2) The reaction is exothermic, but the Keppel generator can't resist heat. 3) Ca(OH)2 produced by the reaction is slightly soluble in water, which will block the lower mouth of the spherical funnel.
3. Can I use a long-necked funnel? No. It is not easy to control the reaction of calcium chloride with water.
4. Why use saturated salt water instead of water?
Used to obtain stable acetylene flow (salt will not react with CaCl 2).
5. What is the effect of putting a ball of cotton near the pilot nozzle in a simple device?
Prevent the generated foam from being ejected from the conduit.
6. Ignite pure methane, ethylene and acetylene. What's the difference between their combustion phenomena?
Light blue flame of methane; Ethylene: bright flame with black smoke acetylene: bright flame with black smoke.
7. In the experiment, acetylene was first introduced into bromine water, then KMnO4(H+) solution, and finally ignited. Why?
The mixture of acetylene and air (or O2) will explode after ignition, which can purify the collected acetylene gas and prevent fire.
8. Acetylene discolors bromine water or KMnO4(H+) solution faster than ethylene. Is it fast or slow? Why?
Acetylene is slow, because the bond energy of triple bonds in acetylene molecule is greater than that of double bonds in ethylene molecule, so it is difficult to break bonds.
High school chemistry formula
1. Non-metallic elements (fluorine, chlorine, oxygen, sulfur, N2, phosphorus, carbon, silicon)
1. oxidation:
F2 + H2 === 2HF
F2+Xe (excess) === XeF2
2F2 (excess)+Xe = = XeF4
NF2+2M === 2MFn (for most metals)
2F2 + 2H2O === 4HF + O2
2. Reducing ability
S + O2 === SO2
S + O2 === SO2
Sulfur +6HNO3 (concentrated) = = sulfuric acid +6NO2+2H2O
3S+4HNO3 (dilution) == 3SO2+4NO+2H2O
N2+oxygen === 2NO
4p+5o2 = = p4o10 (often written as P2O5)
2p+3x2 = = 2px3 (X represents F2, Cl2, Br2)
3. Disproportionation (in alkali)
Cl2 + H2O === HCl + HClO
(Adding acid to inhibit disproportionation, adding alkali or light to promote disproportionation)
Cl2 + 2NaOH === NaCl + NaClO + H2O
2cl 2+2Ca(OH)2 = = = CaCl 2+Ca(ClO)2+2H2O
3Cl2+6KOH (heat concentration) == 5KCl+KClO3+3H2O
High school chemistry must recite knowledge.
1. Experiments using thermometers:
① Determination of solubility; ② Laboratory ethylene production; ③ Petroleum fractionation. The first two should be immersed in the solution.
2. Experiment of using water bath heating in middle school;
(1) Determination of solubility (with thermometer); ② Silver mirror reaction. ③ Hydrolysis of ester.
3. The purpose of the glass rod:
① stirring; ② Drainage; (3) initiating reaction: placing the iron bath S powder mixture on an asbestos net, and initiating the reaction between them with a red-hot glass rod on an alcohol lamp; (4) transferring solids; ⑤ Take the solution; ⑥ Paste the test paper.
4. Substances that deteriorate due to the action of carbon dioxide in the air:
Quicklime, NaOH, Ca(OH)2 solution, Ba(OH)2 solution, NaAlO2 solution, water glass, soda lime, bleaching powder, sodium phenolate solution, Na2O and Na2O2.
5. Substances that deteriorate due to the action of H2O in air:
Desiccant, such as concentrated H2SO4, P2O5, silica gel, CaCl2, alkaline lime, concentrated H3PO4, anhydrous copper sulfate, CaC2, surface alkali, NaOH solid and quicklime;
6. Substances deteriorated due to the oxidation of oxygen in the air:
Sodium, potassium, white phosphorus and red phosphorus, NO, natural rubber, phenol, divalent sulfur (aqueous solution of bisulfate or sulfide),+tetravalent sulfur (aqueous solution of SO2 or sulfite), ferrous salt solution and Fe(OH)2.
7. Deterioration due to volatilization or self-decomposition:
AgNO3, concentrated nitric acid, h? 2O2, liquid bromine, concentrated ammonia, concentrated HCl and Cu(OH)2.
8. When heating the test tube, it should be heated evenly first, and then heated locally.
9. When collecting gas by drainage, first take out the catheter and withdraw the alcohol lamp.
10. When making gas, check the air tightness before charging.
1 1. When collecting gas, exhaust the air in the device before collection.
12. 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.
13. When igniting combustible gases such as H2, CH4, C2H4 and C2H2, check the purity before igniting.
14. When testing halogen elements of halogenated hydrocarbon molecules, add dilute HNO3 to the hydrolysis solution, and then add AgNO3 solution.
15. Before contact with gas, test NH3 (with red litmus paper) and Cl2 (with starch KI paper) by wetting the test paper with distilled water.
16. When preparing easily hydrolyzable salt solutions such as FeCl3 _ 3 and SnCl2 _ 2, first dissolve them with a small amount of concentrated hydrochloric acid and then dilute them.
17 ... flame reaction experiment, every time you do it, you should soak the platinum wire in dilute hydrochloric acid, burn it on the flame until it is colorless, and then do the next experiment.
18. 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.
19. When preparing the substance concentration solution, first add distilled water to the graduation line of the volumetric flask with a beaker of 25px~50px, and then add water to the graduation line with a rubber dropper.
20. When installing the generator, follow the principle of bottom-up, first left and then right or first down and then up, first left and then right.
2 1. If concentrated H2SO4 is accidentally splashed on the skin, it should be washed with water first, and then coated with 3%-5% NaHCO3 solution. When stained with other acids, it should be washed with water first, and then coated with NaHCO3 solution.
22. The lye is stained on the skin, then washed with water and coated with boric acid solution.
23. 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.
24. When checking whether sucrose, starch and cellulose are hydrolyzed, first add NaOH solution to neutralize H2SO4, then add silver ammonia solution or Cu(OH)2 suspension, and heat.
25. 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 displayed on the test paper with the standard colorimetric card to determine the pH value. ..
26. When preparing and preserving salt solutions that are easily hydrolyzed and oxidized by air, such as Fe2+ and Sn2+; Boil distilled water first (drive off O2, then dissolve it, and add a small amount of corresponding metal powder and corresponding acid.
27. When weighing drugs, first put two sizes on each plate; Paper of the same quality (caustic medicine NaOH is put in glassware such as beaker), and then the medicine is put in. The heated medicine should be cooled first and then weighed.
Knowledge points of high school chemistry competition 202 1 related articles;
★ 202 1 Latest General Edition Senior Three Graduation Speech.
★ Work plan of school chemistry teaching and research group
★ 5 Personal narrative of teachers' teaching and educating people
★ Reference for Senior High School Students' Learning Summary Report
★202 1 When do primary and secondary schools in Guangdong have winter holidays?
★ Five-person study plan for winter vacation 202 1
★ 202 1 new semester work plan for chemistry teachers in senior three.
★ The comprehensive quality of senior high school is 500 words.
★ 202 1 Work Plan of Chemistry Teachers in Senior Two for the New Term
★ Annual Work Report of Senior High School Chemistry Teachers