1. Magnesium burns in air: 2Mg+O2 ignites 2MgO.
Phenomenon: (1) gives off dazzling white light (2) gives off heat (3) produces white powder.
2. Iron burns in oxygen: 3Fe+2O2 ignites Fe3O4.
Phenomenon: (1) burning violently, Mars radiation (2) releasing heat (3) generating black solid.
Note: put a small amount of water or fine sand at the bottom of the bottle to prevent the generated solid matter from splashing and cracking the bottom of the bottle.
4. Copper is heated in air: 2Cu+O2 △ 2CuO phenomenon: copper wire turns black.
6. Aluminum burns in air: 4Al+3O2 ignites 2Al2O3.
Phenomenon: it emits dazzling white light, releases heat and produces white solids.
7. Combustion in hydrogen and air: 2H2+O2 ignites 2H2O.
Phenomenon: (1) light blue flame (2) heat release (3) water mist on the inner wall of beaker.
8. Red (white) phosphorus burns in air: 4P+5O2 ignites 2P2O5.
Phenomenon: (1) gives off white light (2) gives off heat (3) gives off a lot of white smoke.
9. Sulfur powder burns in air: S+O2 ignites SO2 phenomenon: A. In pure oxygen.
Give off a bright blue-purple flame, give off heat, and produce a pungent gas.
B, burning in the air
(1) gives off light blue flame (2) gives off heat (3) gives off gas with pungent smell.
10. Carbon burns completely in oxygen: C+O2 ignites CO2.
Phenomenon: (1) white light (2) heat (3) clarified limewater becomes turbid.
1 1. Incomplete combustion of carbon in oxygen: 2C+O2 ignites 2CO.
12. Carbon dioxide passes through the hot carbon layer: C+CO2 at high temperature (it is an endothermic reaction).
13. Carbon monoxide burns in oxygen: 2CO+O2 ignites 2CO2.
Phenomenon: blue flame, exothermic, clear limewater becomes turbid.
14, the reaction of carbon dioxide with water (carbon dioxide turns into purple litmus test solution):
CO2+H2O === H2CO3 phenomenon: litmus test solution turns from purple to red.
Note: Acid oxide+water → acid.
For example, SO2+H2O = = H2SO4, SO3+H2O = = = H2SO4.
15, quicklime dissolved in water: CaO+H2O === Ca(OH)2 (this reaction is exothermic).
Note: Basic oxide+water → alkali.
Sodium oxide dissolved in water: Na2O+H2O =2NaOH.
Potassium oxide is soluble in water: K2O+H2O=2KOH.
Barium oxide is soluble in water: Bao+H2O = = = Ba (OH) 2.
16. Sodium burns in chlorine: 2Na+Cl2 ignites 2NaCl.
17, anhydrous copper sulfate as desiccant: cuso 4+5H2O = = = = cuso 4·5H2O.
Second, the decomposition reaction:
17, water decomposition under the action of direct current: 2H2O charged 2H2 =+O2 =
Phenomenon: (1) There are bubbles on the electrode. H2: oxygen =2: 1
The gas produced by the positive electrode can be used to rekindle the wooden strips with Mars.
The gas produced by the cathode can be burned in the air to produce a light blue flame.
18, heating basic copper carbonate: Cu2 (OH) 2co3 △ 2cuo+H2O+CO2 =
Phenomenon: the green powder turns black, water drops form on the inner wall of the test tube, and the clarified lime water becomes turbid.
19, heating potassium chlorate (adding a small amount of manganese dioxide): 2kcl3omno22kcl+3o2 =
20. heating potassium permanganate: 2kmno4 △ k2mno4+MnO2+O2 =
2 1, oxygen production with hydrogen peroxide in the laboratory: 2H2O2 MnO2 2H2O+ O2↑ =
Phenomenon: bubbles are generated, and the wooden strips with mars are re-ignited.
22. Heating mercury oxide: 2HGO2HG+O2 =
23. Calcined limestone: CaCO3 CaO+CO2↑ = (industrial preparation method of carbon dioxide)
24. Carbonic acid is unstable and decomposed: H2CO3 === H2O+CO2↑ =
Phenomenon: litmus test solution changes from red to purple.
25. Thermal decomposition of copper sulfate crystal: CuSO4 5H2O heats CuSO4+5H2O.
Third, the displacement reaction:
(1) elemental metal+acid salt+hydrogen (displacement reaction)
26. Reaction of zinc with dilute sulfuric acid: Zn+Zn+H2SO4 === ZnSO4+H2↑ =
27. Reaction of magnesium with dilute sulfuric acid: mg+Mg+H2SO4 === MgSO4+H2↑ =
28. Reaction of aluminum with dilute sulfuric acid: 2al+3H2SO4 = = Al2 (SO4) 3+3H2 =
29. The reaction between zinc and dilute hydrochloric acid: Zn+2 HCl = = = ZnCl 2+H2.
30. Reaction of magnesium with dilute hydrochloric acid: mg Mg+ 2HCl === MgCl2+H2↑ =
3 1. Reaction of aluminum with dilute hydrochloric acid: 2al+6hcl = = 2alcl3+3h2 =
26-3 1 phenomenon: bubbles are generated.
32. Reaction of iron with dilute hydrochloric acid: Fe+2 HCl = = FeCl 2+H2 =
33. Reaction of iron with dilute sulfuric acid: Fe+Fe+H2SO4 === FeSO4+H2↑ =
Phenomenon 32-33: bubbles are generated, and the solution changes from colorless to light green.
(2) Simple metal+salt (solution)-another metal+another salt
36. The reaction between iron and copper sulfate: Fe+CuSO4==Cu+FeSO4.
Phenomenon: the surface of the iron bar is covered with a layer of red substance, and the solution changes from blue to light green.
(In ancient copper hydrometallurgy, "Zeng Qing got iron and then turned to copper" refers to this reaction. )
40. Put zinc sheet into copper sulfate solution: CuSO4+Zn==ZnSO4+Cu.
Phenomenon: the surface of zinc sheet is covered with a layer of red substance, and the solution changes from blue to colorless.
4 1. Put the copper sheet into silver nitrate solution: 2AgNO3+Cu==Cu(NO3)2+2Ag.
Phenomenon: The copper sheet is covered with a layer of silver white material, and the solution turns from colorless to blue.
(3) metal oxide+charcoal or hydrogen → metal+carbon dioxide or water
38. Coke reduces iron oxide: 3C+ 2Fe2O3, high temperature 4Fe+3CO2↑ =
39. Reduction of copper oxide with charcoal: 2Cu, high temperature 2Cu+CO2↑ =
Phenomenon: the black powder does not turn red, and the clarified limewater becomes turbid.
25. Reduction of copper oxide by hydrogen: H2+CuO △ Cu+H2O.
Phenomenon: black powder turns red, and water droplets form on the inner wall of the test tube.
34. Reaction of magnesium with copper oxide: magnesium+copper oxide+magnesium oxide.
35. Reaction between hydrogen and iron oxide: Fe2O3+3H2 2Fe+3H2O.
37. Water vapor passes through the hot carbon layer: H2+CO+C, high temperature H2+Co.
Fourthly, the metathesis reaction:
1, basic oxide+acid → salt ++H2O
fe2o 3+6h cl = = 2 FeCl 3+3H2O fe2o 3+3h2so 4 = = Fe2(SO4)3+3H2O
CuO+h2so 4 = = cuso 4+H2O ZnO+2 HNO 3 = = Zn(NO3)3+H2O
2. Alkali+acid → salt ++H2O
Copper hydroxide+dihydrochloride = = copper chloride+copper sulfate dihydrate = = copper sulfate+copper sulfate dihydrate
NaOH+HCl = = NaCl+H2O 2 NaOH+h2so 4 = = na2so 4+2H2O
NaOH+HNO 3 = = nano 3+H2O Mg(OH)2+2 HNO 3 = = Mg(NO3)2+2H2O
ba(OH)2+h2so 4 = = baso 4←+2H2O
3. Acid+salt → new salt+new acid
CaCO3+2 HCl = = CaCl 2+H2O+CO2↑na2co 3+2 HCl = = 2 NaCl+H2O+CO2↑
HCl+agno 3 = = AgCl↓+HNO 3 h2so 4+bacl 2 = = baso 4↓+2 HCl
ba(NO3)2+h2so 4 = = baso 4↓+2 HNO 3 nah co 3+HCl = = NaCl+H2O+CO2↑
4. Salt 1+ salt 2→ new salt 1+ new salt 2
KCl+ silver nitrate = = silver chloride ↓+potassium nitrate, sodium chloride+silver nitrate = = silver chloride ↓+sodium nitrate
na2so 4+bacl 2 = = baso 4↓+2 NaCl bacl 2+2 agno 3 = = 2 AgCl ↓+ Ba(NO3)2
5, salt+alkali → new salt+new alkali
cuso 4+2 NaOH = = Cu(OH)2↓+na2so 4 FeCl 3+3 NaOH = = Fe(OH)3 ↓+ 3 NaCl
ca(OH)2+na2co 3 = = CaCO3↓+2 NaOH NaOH+NH4Cl = = NaCl+NH3 ↑+ H2O
Verb (short for verb) Other reactions:
1, carbon dioxide is converted into clear limewater:
CO2+Ca(OH)2 = = CaCO3↓+H2O phenomenon: clear limewater becomes turbid.
(CO2 can be tested with clarified limewater, and CO2 can also be used to test limewater. )
2. The reaction between calcium hydroxide and sulfur dioxide: SO2+Ca(OH)2 = = caso 3+H2O.
3. The reaction between calcium hydroxide and sulfur trioxide: SO3+Ca(OH)2 = = caso 4+H2O.
4. Reaction of sodium hydroxide with carbon dioxide (carbon dioxide removal): 2NaOH+CO2 ==== Na2CO3+H2O.
5. The reaction between sodium hydroxide and sulfur dioxide (removing sulfur dioxide): 2 NaOH+SO2 = = = Na2SO3+H2O.
6. The reaction between sodium hydroxide and sulfur trioxide (removing sulfur trioxide): 2 NaOH+SO3 = = = Na2SO4+H2O.
Note: 1-6 are: acid oxide+alkali salt+water.
7. Methane burns in air: CH4+2O2 ignites CO2+2H2O.
Phenomenon: a bright blue flame is emitted, and there are water droplets on the inner wall of the beaker, and the clarified lime water becomes turbid.
8. Alcohol burns in air: C2H5OH+3O2 ignites 2CO2+3H2O.
Phenomenon: blue flame, water droplets on the inner wall of beaker, and clear lime water becomes turbid.
9. Reduction of copper oxide by carbon monoxide: CO+ CuO heats Cu+CO2.
Phenomenon: the black powder does not turn red, and the clarified limewater becomes turbid.
10, carbon monoxide reducing iron oxide: 3CO+ Fe2O3, high temperature 2Fe+3CO2.
Phenomenon: the red powder does not turn black, and the clear limewater becomes turbid. (Main reaction principle of ironmaking)
1 1, reduction of ferrous oxide by carbon monoxide: FeO+CO, high temperature Fe+CO2.
12, reducing ferroferric oxide with carbon monoxide: Fe3O4+4CO, high temperature 3Fe+4CO2.
13, photosynthesis: 6CO2+6H2O illumination C6H 12O6+6O2.
14, glucose oxidation: c6h12o6+6o2 = = 6co2+6o2.
Memory class
Summary of junior high school chemistry knowledge (memory part)
I. Scientific names, common names and chemical formulas of substances
(1) diamond, graphite: C (2) mercury, mercury: Hg (3) quicklime, calcium oxide: CaO(4) dry ice (solid carbon dioxide): CO2 (5) hydrochloric acid, hydrochloric acid: HCl(6) sulfurous acid: H2SO4 (7) bisulfate: H2S (8). Soda soda crystal: Na2CO310h2o (11) sodium bicarbonate, acidic sodium carbonate: NaHCO3 (also called baking soda) (12) vitriol, blue vitriol and copper sulfate crystal: CuSO4 5h2o (13). 2CO3 (substance decomposed into three oxides) (14) methanol: CH3OH is toxic, blinding and dead (15) alcohol, ethanol: C2H5OH (16) acetic acid, acetic acid (16℃ glacial acetic acid) ch3c. Ammonia gas: NH3 (basic gas) (18) ammonia water, ammonia monohydrate: NH3·H2O (a common alkali with universality of alkali, which contains no metal ions) (19) sodium nitrite: NaNO2 (industrial salt, toxic).
Second, the color state of common substances
1, white solid: MgO, P2O5, CaO, NaOH, Ca(OH)2, KClO3, KCl, Na2CO3, NaCl and anhydrous CuSO4；; Iron and magnesium are silvery white (mercury is silvery white liquid)
2. Black solid: graphite, carbon powder, iron powder, CuO, MnO2, Fe3O4▲KMnO4 are purple-black.
3. Red solids: Cu, Fe2O3, HgO, red phosphorus ▲ Sulfur: pale yellow ▲ Cu2(OH)2CO3 is green.
4. Color of solution: Any solution containing Cu2+ is blue; Any solution containing Fe2+ is light green; Any solution containing Fe3+ is brown, and other solutions are generally not colorless. (Potassium permanganate solution is purplish red)
5. Precipitation (that is, salt and alkali are insoluble in water): ① Salt: white ↓:CaCO3, BaCO3 (soluble in acid), AgCl, BaSO4 (insoluble in dilute HNO3), etc. ② Alkali: blue: Cu (OH) 2 reddish brown: Fe (OH) 3 white: remaining alkali.
6.( 1) Gases with irritating gases: NH3, SO2 and HCl (all colorless).
(2) Colorless and odorless gases: O2, H2, N2, CO2, CH4 and CO (highly toxic).
▲ Note: Liquid with pungent smell: hydrochloric acid, nitric acid and acetic acid. Alcohol is a liquid with a special gas.
7. Toxic, gas: CO liquid: CH3OH solid: NaNO2 CuSO4 (can be used as a bactericide, mixed with hydrated lime to make a blue viscous substance-Bordeaux liquid).
Third, the solubility of substances.
1, salt solubility
Substances containing potassium, sodium, nitrate and ammonium are all soluble in water.
Only AgCl is insoluble in water, others are soluble in water.
Only BaSO4 is insoluble in water, others are soluble in water.
Only K2CO3, Na2CO3 and (NH4) CO32- are soluble in water, while others are insoluble in water.
2. Solubility of alkali
Alkalis soluble in water include barium hydroxide, potassium hydroxide, calcium hydroxide, sodium hydroxide and ammonia water, while other alkalis are insoluble in water. Fe(OH)3 is red-brown precipitate, Cu(OH)2 is blue precipitate, and other insoluble bases are white. (including Fe(OH)2) Note: AgCl and BaSO4 in sediments are insoluble in dilute nitric acid.
Other precipitates can be dissolved in the acid. Such as: mg (oh) 2co3 baco3 ag2co3, etc.
3. Acids and acidic oxides are mostly soluble in water, while (acidic oxide+water → acid) basic oxides are mostly insoluble in water and partially soluble: barium oxide, potassium oxide, calcium oxide and sodium oxide (basic oxide+water → alkali).
Fourth, the most in chemistry.
1. The most abundant metal element in the earth's crust is aluminum. 2. Oxygen is the most abundant nonmetallic element in the earth's crust.
The most abundant substance in the air is nitrogen. The hardest substance in nature is diamond.
5. The simplest organic matter is methane. 6. The most active metal in the metal activity sequence table is potassium.
7. The oxide with the smallest relative molecular mass is water. The simplest organic compound CH4
8. Under the same conditions, the gas with the lowest density is hydrogen. 9. The most conductive metal is silver.
10, and the atom with the smallest relative atomic mass is hydrogen. 1 1, and the metal with the smallest melting point is mercury.
12, the most abundant element in human body is oxygen. 13, the element that constitutes the most kinds of compounds is carbon.
14, the most widely used metal in daily life is iron. 15, China first used natural gas; The largest coal base in China is: Shanxi Province; The earliest application of copper hydrometallurgy was China (discovered in the Western Han Dynasty [Liu An's "Huainan Wanbi Book" Zeng Qing De Tiehua Copper]] and applied in the Song Dynasty); The earliest discovery of electrons was Thomson of England; Lavoisier, a Frenchman, first came to the conclusion that air is composed of N2 and oxygen.
Five, the "three" in junior high school chemistry
1. The three kinds of particles that make up matter are molecules, atoms and ions.
2. Hydrogen, carbon monoxide and carbon, which are usually used to reduce copper oxide.
3. As a fuel, hydrogen has three advantages: rich resources and high calorific value, and the product after combustion is water that does not pollute the environment. There are generally three kinds of particles that make up atoms: protons, neutrons and electrons. There are only three kinds of ferrous metals: iron, manganese and chromium. 6. Elements that make up a substance can be divided into three categories, namely (1) metallic elements, (2) nonmetallic elements and (3) rare gas elements. 7. There are three kinds of iron oxides, and their chemical formulas are (1)FeO, (2)Fe2O3 and (3) Fe3O4.
8. The characteristic of the solution is three (1) homogeneous; (2) stability; (3) mixture.
9. The chemical equation has three meanings: (1) indicates what substances participate in the reaction and what substances are generated as a result; (2) The particle number ratio of molecules or atoms between reactants and products; (3) Represents the mass ratio of each reactant and product. Chemical equations have two principles: based on objective facts; Follow the law of conservation of mass. 10 pig iron is generally divided into white iron, gray iron and ductile iron.
Carbon steel can be divided into three types: high carbon steel, medium carbon steel and low carbon steel.
12. There are three kinds of iron ore commonly used in ironmaking: (1) hematite (mainly Fe2O3); (2) Magnetite (Fe3O4); (3) siderite (FeCO3). There are mainly three kinds of steelmaking equipment: converter, electric furnace and open hearth furnace.
14. The three reaction conditions that are often related to temperature are ignition, heating and high temperature.
15. There are two ways to change saturated solution into unsaturated solution: (1) heating, (2) adding solvent; There are three methods to change unsaturated solution into saturated solution: cooling, adding solute and evaporating solvent at constant temperature. (Note: For substances whose solubility decreases with temperature, such as calcium hydroxide solution changes from saturated solution to unsaturated solution: cool and add solvent; There are three ways to change unsaturated solution into saturated solution: raising temperature, adding solute and evaporating solvent at constant temperature.
16. There are generally three methods to collect gas: drainage, upward evacuation and downward evacuation.
17, three main causes of water pollution: (1) waste residue, waste gas and waste water in industrial production; (2) Discharging domestic sewage at will; (3) Pesticides and fertilizers used in agricultural production flow into rivers with rainwater.
18, there are three commonly used fire extinguishers: foam extinguisher; Dry powder fire extinguisher; Liquid carbon dioxide fire extinguisher.
19. The change of solubility of solid substances with temperature can be divided into three categories: (1) The solubility of most solid substances increases with the increase of temperature; (2) The solubility of a few substances is little affected by temperature; (3) The solubility of a few substances decreases with the increase of temperature. 20.CO2 can put out fires for three reasons: it can't burn, it can't help combustion, and its density is higher than that of air. 2 1, simple substances can be divided into three categories: metallic simple substances; Non-metallic simple substance; Simple substance of rare gas. 22. The three most important fossil fuels in the world today are coal, oil and natural gas.
23. The three black oxides that should be remembered are copper oxide, manganese dioxide and ferroferric oxide.
24. Hydrogen and carbon have three similar chemical properties: stability at room temperature, flammability and reducibility.
25. There are three times of light blue in the textbook: (1) liquid oxygen is light blue (2) sulfur burns in the air with a weak light blue flame (3) hydrogen burns in the air with a light blue flame.
26. Three blue colors related to copper: (1) copper sulfate crystal; (2) copper hydroxide precipitation; (3) copper sulfate solution. 27. The filtration operation has "triple inclination": (1) The lower end of the funnel is close to the inner wall of the beaker; (2) the end of the glass rod gently leans against the third layer of filter paper; (3) The edge of the beaker containing the liquid to be filtered is close to the glass frame for drainage.
28. Three major gas pollutants: SO2, CO and NO2.
29. The flame of alcohol lamp is divided into three parts: external flame, internal flame and flame core, of which the external flame has the highest temperature.
30. There are three noes in taking and using drugs: (1) Don't touch drugs with your hands; (2) Don't put your nose to the mouth of the container to smell the smell of gas; (3) Do not taste medicine. 3 1. Three ancient chemical processes: papermaking, gunpowder making and porcelain burning. Industrial waste: waste water, waste residue and waste gas.
34. Three kinds of instruments that can be directly heated: test tube, crucible, evaporating dish (and burning spoon).
35. The three atoms explained by the conservation of mass remain the same: the species remains the same, the quantity remains the same, and the mass remains the same.
36. Mixing with air ignites three potentially explosive gases: H2, carbon monoxide and methane (virtually any combustible gas and dust). 37. Three products of coal dry distillation (chemical change): coke, coal tar and coke oven gas.
38. Three characteristics of concentrated sulfuric acid: water absorption, dehydration and strong oxidation.
39. There are three prohibitions on the use of alcohol lamps: burning lamps, burning lamps with alcohol, and blowing mouths.
40. Three steps of solution preparation: calculation, weighing (measurement) and dissolution.
4 1, the first three elements with the most content in biological cells: O, C and H.
42. Three equations in atoms: nuclear charge number = proton number = extranuclear electron number = atomic number.
43. Three kinds of particles make up matter: molecules, atoms and ions.
Six, "certain" and "not necessarily" in chemistry
1, chemical changes must have physical changes, and physical changes may not necessarily have chemical changes.
2. Metals are not always solid at room temperature (for example, mercury is liquid), and nonmetals are not always gas or solid (for example, Br2 is liquid). Note: Metals and nonmetals refer to simple materials and should not be confused with material elements.
3. Atomic groups must be charged ions, but not necessarily acidic groups (such as NH4+, OH-);
Acid radical is not necessarily an atomic group (for example, Cl-is called hydrochloric acid radical).
4. Slow oxidation may not cause spontaneous combustion. Combustion must be a chemical change. The explosion is not necessarily a chemical change. (For example, the explosion of a pressure cooker is a physical change. There are not always neutrons in the nucleus (for example, there are no neutrons in the H atom). 6, the atom is not necessarily smaller than the molecule (can't say "the molecule is big, the atom is small")
The fundamental difference between molecules and atoms is that in chemical reactions, molecules can be separated and atoms cannot be separated.
7. A substance composed of the same element is not necessarily a simple substance, but may be a mixture of several simple substances.
8. Particles with the outermost electron number of 8 are not necessarily atoms of rare gas elements, but may also be cations or anions. 9. The outermost electron number of atoms with stable structure is not necessarily 8. (The first layer is the outermost two electrons) 10, particles with the same nuclear charge number are not necessarily the same element.
(Because particles include atoms, molecules and ions, while elements do not include molecules or atomic groups composed of polyatomic atoms) Only mononuclear particles (one atom and one nucleus) with the same nuclear charge must belong to the same element.
1 1 and (1) concentrated solutions are not necessarily saturated solutions; A dilute solution is not necessarily an unsaturated solution. (For different solutes) (2) A saturated solution of the same substance is not necessarily thicker than an unsaturated solution. (Because the temperature is uncertain, just as the temperature is certain) (3) The solution after crystal precipitation must be a saturated solution of something. After the saturated solution is cooled, the crystal does not necessarily precipitate. (4) At a certain temperature, the solubility of any substance must be greater than the solute mass fraction of its saturated solution, that is, S must be greater than C. ..
13, the reaction between simple materials and the compound is not necessarily a displacement reaction. But the valence of elements must have changed. 14, the valence of elements does not necessarily change in decomposition reaction and combination reaction; The valence of elements must change in the displacement reaction; In the metathesis reaction, the valence of elements must remain unchanged. (Note: the valence of elements must change in the redox reaction) 15, the simple substance must not be decomposed.
16, the same element in the same compound does not necessarily show a valence. For example, NH4NO3 (front n is -3 and back n is +5).
17, the composition of salt does not necessarily contain metal elements. For example, NH4+ is a cation with the properties of metal ions, but it is not a metal ion. 18, the cation is not necessarily a metal ion. Such as H+ and NH4+.
19, in the composition of compounds (oxide, acid, alkali, salt), oxide and alkali must contain oxygen; Acids and salts do not necessarily (possibly) contain oxygen; Acids and bases must contain hydrogen; It is salts and oxides that do not necessarily contain hydrogen; The composition of salt and alkali does not necessarily contain metal elements (such as NH4NO3 and NH3 H2O); Acid components can contain metallic elements (for example, HMnO4 is called permanganate), but all material components must contain nonmetallic elements. 20, salt solution is not necessarily neutral. For example, Na2CO3 solution is alkaline.
2 1, the acid salt solution is not necessarily acidic (that is, the PH is not necessarily less than 7), such as the NaHCO3 solution is alkaline. But the sodium bisulfate solution is acidic (NaHSO4 =Na++H+ +SO42-), so the substance that can ionize hydrogen ions is not necessarily an acid.
22. The acid solution must be an acid solution, but the acid solution is not necessarily an acid solution. For example, H2SO4 and NaHSO4 are both acidic, while NaHSO4 is a salt. (The acidic solution is an acidic aqueous solution, and the acidic solution is a solution containing H+)
23. The alkaline solution must be an alkaline solution, but the alkaline solution is not necessarily an alkaline solution. For example, NaOH, Na2CO3 and NaHCO3 solutions are all alkaline, while Na2CO3 and NaHCO3 are salts. The alkaline solution is an aqueous solution of alkali, and the alkaline solution is a solution containing OH-
24. Basic oxides must be metal oxides, and metal oxides are not necessarily basic oxides.
(For example, Mn2O7 is a metal oxide, but it is an acid oxide, and its corresponding acid is permanganate, that is, HMNO 4); Remember: only K2O, Na2O, BaO and CaO in basic oxides can be dissolved in water and react with water to form alkali.
25. Acidic oxides are not necessarily nonmetallic oxides (such as Mn2O7), and nonmetallic oxides are not necessarily acidic oxides (such as H2O, CO and NO). ★ Common acidic oxides: CO2, SO2, SO3, P2O5, SiO2, etc. Most acidic oxides can be dissolved in water and react with water to generate corresponding acids. Remember that silicon dioxide (SiO2) is insoluble in water.
26. The reaction between salt and water is not necessarily a neutralization reaction.
27. All chemical reactions do not necessarily belong to the basic reaction type. Those that do not belong to the basic reaction are: ① the reaction between co and metal oxides; (2) the reaction of acid oxide with alkali; ③ Combustion of organic matter.
28. All elemental iron participates in the displacement reaction (iron reacts with acid and salt), and the iron after the reaction must be +2 valence (i.e. ferrous salt is generated). 29. Where there is a displacement reaction between metal and acid, the quality of the solution will inevitably increase after the reaction.
When a metal reacts with a salt solution, we can judge the quality change of the solution before and after the reaction only by looking at the relative atomic mass of the metal participating in the reaction and the relative atomic mass of the metal generated. "Promote the small with the big, and promote the big with the small"
30. Whenever a metal with the same mass and valence reacts with an acid, the greater the relative atomic mass, the less hydrogen is produced. 3 1. Any metal that can react with water at room temperature (such as K, Ca, Na) must not react with salt solution; But they react most violently with acids.
If Na is added to CuSO4 solution, the reaction will be: 2Na+2H2O = 2NaOH+H2 ↑; 2NaOH+CuSO4 =Cu(OH)2 ↓+Na2SO4 .
3 1. All exhaust methods (upward or downward) must extend the air duct to the bottom of the gas container.
32, preparation of gas generator, be sure to check the air tightness before charging.
Before ignition or heating, be sure to check the purity of combustible gas.
33. When writing a chemical formula, all positive valence elements are not necessarily written on the left. Such as NH3 and CH4
34, 5g of a substance into 95g of water, fully dissolved, the solute mass fraction of the solution is not necessarily equal to 5%.
Can be equal to 5%, such as NaCl, KNO3, etc. It can also be greater than 5%, such as, Na2O, BaO, etc. It may also be less than 5%, such as crystalline hydrate and Ca(OH)2, CaO, etc.
◆ Under the same conditions, CaO or Ca(OH)2 is dissolved in water to obtain the smallest solute mass fraction.