List of high school chemistry knowledge points

Today, I have compiled a summary of 300 knowledge blind spots in high school chemistry! ! See what you have.

Passivation phenomenon: Iron and aluminum are passivated in cold concentrated nitric acid or concentrated sulfuric acid. Passivation is only used at room temperature, and iron will react with concentrated sulfuric acid under heating conditions.

Passivation of 2Fe+6H2SO4 (concentrated) =Fe2(SO4)3+ 3SO2↑+6H2O means that the surface of active metal is oxidized in strong acid to form a dense oxide film to organize the further reaction of metal.

2. In ionic equation, concentrated hydrochloric acid and concentrated nitric acid decompose, but concentrated sulfuric acid does not.

3. In ionic equation, clear limewater should be decomposed into ions, while turbid limewater should not be decomposed.

4. Where there are anions, there must be cations, and if there are cations, there may be no anions. For example, there are only free electrons in metals.

5. Sodium hydroxide does not react with ethanol.

6. The pitfalls of Avogadro constant test sites include: the volume is not public, for example, in hydrochloric acid solution with PH= 1, the number of hydrogen ions is 0. 1NA.

7. There is no C=C double bond in benzene.

8. Sodium carbonate, commonly known as soda ash and soda, is alkaline but not alkali, but salt. (stable)

9. Baking soda is sodium bicarbonate, which is decomposed into sodium carbonate, carbon dioxide and water by heating. (instability) will be found in the inference question.

10, acetic acid, phenol, water and ethanol, the activity of hydrogen atoms on hydroxyl groups in the molecule decreased in turn. Therefore, sodium hydroxide does not react with ethanol.

1 1, the melting point of alkali metal elements is that the larger the atomic radius, the lower the melting point; Halogen is a molecular crystal, which is bonded by van der Waals force. The magnitude of van der Waals force is related to molecular weight. The greater the molecular weight, the greater the Van der Waals force and the higher the melting point. The alkali metal element is a metal crystal and the bonding bond is a metal bond. The smaller the atomic radius, the stronger the attraction between nuclei, the harder it is to destroy and the higher the melting point. # With the increase of nuclear charge, the melting point gradually decreases (contrary to halogen and oxygen).

12, lithium reacts with oxygen to generate only lithium oxide, sodium generates sodium oxide at room temperature, and sodium peroxide is generated by heating or complete combustion.

13. Particularity of alkali metals: Lithium is less dense than kerosene, so it cannot be stored in kerosene. It is usually sealed in paraffin, and sodium is less dense than water and more dense than kerosene.

14, the density of alkali metals gradually increases from lithium to cesium, but the density of sodium is abnormally higher than that of potassium.

15, the solubility of acid salt is generally greater than the corresponding normal salt, but the solubility of sodium carbonate is greater than that of sodium bicarbonate.

16. Dry distillation of coal is a chemical change, while distillation and fractionation are physical changes.

Protein's denaturation is a chemical change, and salting-out is a physical change.

18, the basic oxide must be a metal oxide, and the metal oxide is not necessarily a basic oxide. Mn2O7 is a metal oxide, but it is an acid oxide, and the corresponding acid is permanganate, that is, HMnO4.

19, acidic oxides are NOt necessarily nonmetallic oxides (such as Mn2O7), and nonmetallic oxides are not necessarily acidic oxides (such as H2O, CO, no).

20. Most acidic oxides are soluble in water and react with water to generate corresponding acids. Remember that silicon dioxide (SiO2) is insoluble in water. The concept of basic oxide: it can react with acid to produce salt and water, and the products can only have salt and water.

2 1, oxidizability: Cl2 >；; Br2 & gtFe3+>； I2 & gts； Reducibility: iodine ion >; Ferrous ion > bromine ion > chloride ion

22, 22.4L, gas, carbon tetrachloride, benzene, water, alcohol, sulfur trioxide, hydrocarbons with more than 4 carbon atoms (neopentane is a gas at standard temperature and pressure) are not gases, and it is necessary to remember whether NO, O2 and other reactions will occur when mixing.

23, hypochlorous acid is a weak electrolyte, ionic equation don't open it.

24. With the progress of the reaction, the concentration will be gradually diluted, so it cannot be carried out to the end, such as the reaction of manganese dioxide with concentrated hydrochloric acid.

25. Water glass is a mixture of soluble silicates such as sodium silicate.

26. preparation method of silver ammonia solution: add dilute ammonia water to AgNO3 solution.

AgNO3 + NH3。 H2O = AgOH↓+NH4NO3

Then add dilute ammonia water: AgOH+2NH3. H2O =Ag(NH3)2 OH+2H2O until the precipitation just stops dissolving.

27. Metaaluminate reacts with hydrogen ions: if it is H+, a small amount of H++H2O+AlO2-=Al(OH)3 ↓ If it is a large amount of H+, AlO2- +4H+=Al3++2H2O.

28. foam extinguisher's reaction principle: application of double hydrolysis method: Al2 (SO4) 3+6 nahco3 = = 3Na2SO4+2al (OH) 3 ↓+6CO2 =

29. Sodium phenolate and carbon dioxide, no matter how much carbon dioxide passes through, only produce sodium bicarbonate, C6H5ONa+CO2+H2O==C6H5OH+NaHCO3.

30, phenol can react with sodium carbonate:

c6h 5-OH+na2co 3-→c6h 5-ONa+nah co 3

This reaction occurs because phenol is more hydrochloric than bicarbonate. Sodium phenolate can only react with carbon dioxide;

c6h 5-ONa+CO2+H2O-→c6h 5-OH+nah co 3

This reaction occurs because carbonic acid is more acidic than phenol.

3 1, phosphorus reacts with chlorine, chlorine is enough to generate phosphorus pentachloride, and chlorine is insufficient to generate phosphorus trichloride.

32. The molecular formula of white phosphorus is P4 and molecular crystal, so the number of phosphorus atoms in 12.4g white phosphorus is 0.4NA.

33.Cl2 reacts with sufficient Fe, regardless of whether the iron is excessive or not, only ferric chloride is generated, and only the iron in the solution reacts with ferric chloride to generate ferrous chloride.

34、Al3++ 3 AlO2- + 6 H2O =4 Al(OH)3↓

35, excessive carbon dioxide into the water glass reaction is:

2H2O+2CO2+Na2SiO3 = 2NahCO3+H2SiO3 ↓ Carbon dioxide can't produce excessive sodium carbonate.

36. Contrast radius: (1) The layers are the same, but the nuclear radius is small; (2) Different nuclear layers; (3) The nuclear layer is the same, but the valence radius is small; For example, iron is greater than bivalent iron and trivalent iron; (4) With the same electron shell structure, the larger the nuclear charge, the smaller the radius.

37.c is the element that forms the most compounds, and the simple substance is the element with the greatest hardness in nature or the element with the highest mass fraction of hydrogen in gaseous hydrides.

38. The gaseous hydride of an element can react with its oxide at room temperature to produce elemental S ... This is a very important chemical reaction in high school and the only one that shows that sulfur dioxide is oxidizing. 2H2S+SO2=2H2O+3S

39. The gaseous hydride of an element can react with the hydrate corresponding to its highest valence oxide to form a salt, and the element is N. ..

40. The nonmetallic element whose simple substance is liquid at room temperature is bromine. The metal element whose simple substance is liquid at room temperature is mercury.

4 1. alloy is a mixture, and its properties are often superior to those of its constituent metals. For example, its hardness is higher than its constituent metal, and its melting point is lower than its constituent metal.

42,3 mg+N2 = = Mg3N22 mg+CO2 = = C+2mog (conditions are all ignited, don't forget, it will be released in the amount of substance, so it is wrong to think that magnesium does not react with nitrogen).

43. The carbon content of pig iron, common iron and stainless steel decreased in turn. Pig iron: Pig iron is an iron-carbon alloy with carbon content greater than 2%, steel: steel is an iron-carbon alloy with carbon content between 0.04% and 2.3%, and stainless steel is an alloy of iron, carbon and chromium, with iron content of about 74.6%.

44. Alum is used to purify water, which is the principle of hydrolysis. The principle is that alum can ionize two kinds of metal ions in water: KAl(SO4)2 = K++Al3++2SO42-, and Al3+ is easily hydrolyzed to form colloidal aluminum hydroxide Al (OH) 3: Al3++3H2O = Al (OH) 3 (colloid)+.

45. Iron or aluminum can be used for sealed storage and transportation of concentrated sulfuric acid or concentrated nitric acid, because iron and aluminum cannot react with concentrated sulfuric acid and concentrated nitric acid. Wrong, not unresponsive. Passivation is the formation of dense oxides on the surfaces of concentrated sulfuric acid, concentrated ferric nitrate and aluminum to prevent metals from contacting with concentrated acid.

46, the reaction of metal aluminum and strong alkali solution, water as oxidant. Not sodium hydroxide. 2Al + 2NaOH + 2H2O = 2NaAlO2 + 3H2↑

47. The combustion of magnesium in sulfur dioxide is similar to that in carbon dioxide, producing magnesium oxide and elemental sulfur, but the generated sulfur can continue to react with magnesium to produce magnesium sulfide. 2Mg+SO2==2MgO+S Mg+S==MgS conditions are all ignited.

48, aluminothermic reaction: iron oxide:

2Al+Fe2O3=Al2O3+2Fe

Ferroferric oxide: 8al+3f3o4 = 4al2o3+9fe

Manganese dioxide: 4Al+3MnO2=2Al2O3+3Mn (reaction conditions are all high temperature) aluminothermic reaction Application: used for smelting rare metals, welding railway tracks in the field and directional blasting.

49, the focus of aluminothermic reaction:

(1) aluminothermic reaction is often used to smelt high melting point metals, and it is an exothermic reaction, in which magnesium rod is used as igniter and potassium chlorate is used as combustion improver.

(2) Principle: The thermite in the thermite reaction device is at the bottom, potassium chlorate is at the top, and magnesium bars are inserted in the middle. In the process of reaction, the magnesium strip is first ignited, and potassium chlorate is decomposed at high temperature to produce oxygen, thus promoting the combustion of magnesium strip. The burning of magnesium bars generates a lot of heat, because thermite reaction requires high temperature conditions, so that the reaction can be carried out.

50, the strength of the metal element judgment method:

(1) How easy it is to react with water or acid to replace hydrogen.

(2) The highest valence oxide corresponds to the alkalinity of hydrate.

(it must be the highest price, and it will be in the multiple-choice question. The trap is to get rid of the highest price. )

(3) Reduction of simple substance or oxidation of ions

(4) Displacement reaction between simple materials.

(5) Electrochemical principle

(6) The position of elements in the periodic table.

5 1, several points to remember in electrochemistry: primary battery: negative oxygen, negative negative positive (what do you mean, the negative electrode is oxidized, the anion moves to the negative electrode, and the cation moves to the positive electrode. Exams generally give multiple-choice questions. As long as you judge who is the negative electrode, it must be oxidized. I don't remember this. Isn't Wahaha a kind of new water called oxygen-rich water?) Haha electrolytic cell: electrolytic cell Remember: positive oxygen is it.

52. The test sites of electrochemistry mainly focus on the following points: (1) Judge who is the negative electrode and the positive electrode; (2) What happened in the direction of ion movement; (4) current movement direction; (5) the direction of electron movement; (6) the number of transferred electrons; (7) Positive and negative equations; (8) Electrochemical corrosion of hydrogen-oxygen fuel cells; (9) Oxygen inhalation corrosion.

53. Remember that galvanic cells and electrolytic cells are not reversible reactions. The reversible reaction is in the same state, that is, the conditions are the same, while the electrolytic cell and the primary cell have an external power supply and one does not.

54. Carbon dioxide electrons can write and can't make mistakes.

55. Do you remember that silicon can also react with sodium hydroxide: Si+2NaOH+H2O==Na2SiO3+2H2 (gas), not just aluminum, depending on the topic, if the metal is aluminum, the nonmetal is silicon.

56. A galvanic cell can be understood as protecting the anode, and an electrolytic cell can be understood as protecting the cathode. So copper smelting or electroplating, crude copper as anode, you can't protect crude copper as cathode, electroplating as anode and electroplating as cathode.

57. Hydrofluoric acid can dissolve many glasses (silica) that other acids can't. The reaction equation is as follows: SiO2(s)+4 HF(aq) → SiF4(g)+2 H2O(l).

58. Iodine turns blue when it meets starch, not iodine in potassium iodide. It is often forgotten when doing problems, for example, iodine in iodized salt can be directly tested with starch, which is wrong.

59. Both aluminum hydroxide and sodium bicarbonate can be used to treat hyperacidity, but sodium carbonate should not be used.

60. The main ingredient of baking powder is baking soda, which is sodium bicarbonate, not sodium carbonate.

6 1. When lithium metal is burned in air, only lithium oxide is produced, and no peroxide is produced.

62. Sulfur dioxide and carbon dioxide do not react with calcium chloride and barium chloride. For example, it is said in the exam that barium chloride solution can produce barium sulfite by introducing sulfur dioxide. Is wrong. It can be remembered that calcium carbonate reacts with hydrochloric acid to produce calcium chloride, carbon dioxide and water, and this reaction is irreversible. Or weak acids can't make strong acids.

63. Equation of failure principle of bleaching powder: The main components of bleaching powder are calcium hypochlorite and calcium chloride. Calcium hypochlorite reacts with carbon dioxide and water vapor in the air to generate calcium carbonate and hypochlorous acid, and hypochlorous acid decomposes to generate hydrogen chloride and oxygen at the sight of light. Because hypochlorous acid has bleaching effect, hypochlorous acid becomes invalid after decomposition. ca(CIO)2+CO2+H2O = CaCO3+2 hcio 2 hcio = 2 HCI+O2

64. Remember substances that are decomposed by light and heat. See photolytic substances: nitric acid, silver iodide, silver bromide, silver chloride, hypochlorous acid. Sodium bicarbonate decomposes when heated.

65. Remember substances that are decomposed by light and heat. See photolytic substances: nitric acid, silver iodide, silver bromide, silver chloride, hypochlorous acid. Sodium bicarbonate decomposes when heated.

66. Redox reaction: We should judge not only the change of valence, but also the reduction products and oxidation products, oxidants and reductants. Tip: oxidation products correspond to redox agents; Obtain a reduction product corresponding to that reduce oxidant. Or remember: the reducing agent corresponds to the oxidation product and the oxidizing agent corresponds to the reduction product. (Oxidants and reductants refer to reactants, and reduction products and oxidation products only refer to products. )

67. The multiple-choice questions will show that C6H6O (phenol) +O2 generates C6H4O2 (benzoquinone Kun) +H2O, which is why phenol turns pink in the air.

68. Although both starch and cellulose conform to the general formula (C6 H 10 O5)n, they are both carbohydrates. Remember that they are not isomers because the values of n are different.

69. Starch, cellulose, protein, silk and natural rubber are all polymer compounds, but oil is not. Synthetic organic polymer compounds (such as polyethylene, polyvinyl chloride, plexiglass, synthetic fiber, synthetic rubber, etc.). )

70. A certain amount of sodium peroxide reacts with a certain amount of carbon dioxide and water vapor, which can be considered as first reacting with carbon dioxide, and then reacting with water after carbon dioxide is completely reacted.

7 1, sodium peroxide reacts with carbon dioxide and water, which can be understood as absorbing CO in carbon dioxide and H2 in water. For example, the national college entrance examination question: take a g to make a substance burn completely in oxygen, and its product completely reacts with enough sodium peroxide solid, and the mass of the solid after the reaction just increases by a g. The following substances cannot meet the above results ()

A.h2b.coc.c6h12o6d.c12h2o11Analysis: A hydrogen burns to generate water, and the reaction of sodium peroxide with water is equivalent to absorbing hydrogen in water, but the symbols are different before and after, and the quality remains unchanged. B carbon monoxide burns to produce water, and the reaction of sodium peroxide with water is equivalent to absorbing CO in carbon dioxide, so it is correct. C can be modified to 6(CO)6(H2), and you can refer to AB. Option d, does not match.

72. Iron reacts with water vapor at high temperature and does not write gas symbols. 3Fe+4H2O==Fe3O4+2H2

73. Charcoal, concentrated sulfuric acid and concentrated nitric acid all produce carbon dioxide. C+2H2SO4 (concentrated) = CO2 =+2so2 =+2h2o; C+4HNO3 (concentrated) =CO2 (gas) +4NO2 (gas) +2H2O.

74. Put 0.3mol of sodium, 0.3 mol of magnesium and 0.3 mol of aluminum into 100 ml of 1 mol L- 1 hydrochloric acid respectively, and the gas volume ratio generated at the same temperature and pressure is ().

A.1:2: 3b.6: 3: 2c.3:1:1D.1:1Analysis: C is the correct answer. Don't forget that excessive sodium will react with water to release hydrogen, while aluminum and magnesium can't react with water. Both of them are excessive. Only the amount of hydrochloric acid can be used to calculate the amount of hydrogen produced.

75. Collect nine questions about the existence of ions in the college entrance examination. This test center appeared three times. What is this? That is, ferrous ions, hydrogen ions and nitrate ions cannot exist, because ferrous ions will be oxidized into trivalent iron ions.

76, ammonium ion can be with hydrogen ion * * *, metaaluminate can be with hydroxide * * *. Or it can be written down like this (metaaluminate ions cannot coexist with hydrogen ions and weak base ions * * *. Ammonium ions cannot coexist with hydroxide ions and weak acid ions. )

77. Hydrocarbons are defined as organic compounds consisting of only two elements of hydrocarbons, also known as hydrocarbons. Hydrocarbons can be divided into chain hydrocarbons (open chain aliphatic hydrocarbons) and cyclic hydrocarbons according to the shape of carbon skeleton. Children's shoes should remember that gasoline, diesel oil and vegetable oil are all mixtures and do not meet the definition of hydrocarbons. For example, bromoethane is not a hydrocarbon, because it contains bromine and can only be called a derivative of hydrocarbons.

78. Hydrogen atoms in hydrocarbon molecules are replaced by other atoms or groups to generate other substances, which are called hydrocarbon derivatives. Such as methyl chloride, nitrobenzene, etc.

79, multiple-choice questions often take an examination of:

When ethylene and benzene are added to bromine water, the fading phenomenon can be observed due to the addition reaction. (error)

Description: (1) Benzene cannot react with bromine water. Benzene can only react with liquid bromine (catalyzed by iron bromide). (2) The difference between liquid bromine and bromine water, liquid bromine is pure and bromine water is a mixture. (3) After mixing benzene and bromine water, bromine can be extracted into benzene, and the inorganic layer is almost colorless, and the organic layer is orange, but there is no reaction. Ethylene is bromine water, and fading is addition because of its double bond. (4) Both carbon tetrachloride and benzene can be used as extractant, but their phenomena are different. Benzene is lighter than water, so the upper and lower layers are colored, while carbon tetrachloride is heavier than water, so the upper layer is colorless and the lower layer is colored. One question, we have summarized many test sites, and children's shoes should be remembered.

80, alcohol oxidation into aldehyde oxidation into acid, aldehyde can be reduced to alcohol. Acids cannot be reduced to aldehydes.

8 1 and flame reaction are physical changes. Why? Because of the sudden transition of electrons, atoms have changed, and atoms and molecules have not changed.

82. Steel corrodes more easily in seawater than in rivers, mainly because of the high oxygen content in seawater. (Wrong) Analysis: I remember why copper sulfate was added to the reaction of iron and dilute sulfuric acid, and the reaction speed became faster because copper and iron could form primary cells. This problem is the same principle. The salt content of seawater is higher than that of river water, which is easy to form galvanic cells and more corrosive.

83. Typical cases of electrochemical corrosion are oxygen and hydrogen absorption corrosion of iron. (1) This reaction constitutes a galvanic cell instead of an electrolytic cell. (2) Hydrogen absorption corrosion occurs under acidic conditions: negative reaction Fe-2e-=Fe2+ positive reaction 2h+2e-= H2 = total reaction Fe+2h+= Fe2+H2 = (3) Oxygen absorption corrosion occurs under neutral or weak acidic conditions: negative electrode Fe-2e-=Fe2+ positive electrode: 2h2o+O2.

2Fe+2H2O+O2=2Fe(OH)2 (or)

4Fe(OH)2+O2+2H2O=4Fe(OH)3

(4) It should be said that the main test is oxygen absorption corrosion.

84. Chemical corrosion: direct reaction. Electrochemistry: A galvanic cell is formed by electric current.

85, ionic equation's true and false judgment:

(1) The reaction equation of sodium bicarbonate solution is different from that of a small amount of limewater and an excessive amount of limewater (remember that it conforms to the principle of a small amount, just like the wooden barrel theory in management, how much water is filled depends on the short board on the left).

A small amount of limewater ionic equation is:

2HCO3-+2OH-+Ca2+=CaCO3 (precipitation) +CO32-+2H2O

Ionic equation with excessive limewater is:

HCO3-+ Ca2+ +OH-=H2O+CaCO3 precipitation symbol

(2) Calcium carbonate, magnesium carbonate and barium carbonate are often forgotten if they are not disassembled in ionic equation.

(3) Lime milk mixed with Na2CO3 solution: Ca2++CO32-= CaCO3 (wrong) Lime milk will not be disassembled. (4) barium carbonate reacts with sulfuric acid: Ba2+SO4 2-= = = baso4 ↓ (error, barium carbonate does not disassemble)

(5) Reaction between copper sulfate and caustic soda: CuSO4+2OH-= = Cu (OH) 2 ↓+SO42- (Wrong, copper sulfate should be disassembled)

(6) The reaction between dilute nitric acid and excess iron filings is 3fe+8h+2no3-= 3fe3+2no↑+4h2o (error). Ionic equation was right, but excessive iron will react with trivalent iron to form divalent iron.

(7) Clear limewater mixed with a small amount of soda solution: Ca2++OH-+HCO3-= CaCO3 ↓+H2O.

(8) (Wrong, this question will be considered right at first glance, and it also conforms to the small proportion relationship, but soda is sodium carbonate and baking soda is sodium bicarbonate, which is the real question of the national college entrance examination. )

(9) Adding excessive ammonia water into the aluminum chloride solution: Al3++4NH3? H2O = AlO2-+4NH4++2H2O (Wrong, this testing center has been testing for several years. I.e. aluminum hydroxide precipitate is insoluble in ammonia water)

(10) drop FeCl3 _ 3 _ 3 solution into boiling water to prepare Fe (OH) _ 3 colloid: Fe3++3H2O _ _ (△) Fe (OH) _ 3 ↓+3h+(error, the colloid is not marked with precipitation symbol, and it is also the test center for several years).

(1 1) Add a small amount of metallic sodium to cold water: Na+2H2O = Na++OH-+H2 ↑ (Wrong, at first glance, parents will think it is correct, the charge is conserved, the products and reactants are correct, but the mass is not conserved) So remember, to judge whether ionic equation is correct, you can look at it first, and then at the charge and mass.

(12) descaling with acetic acid: CaCO3+2h+= = Ca2+H2O+CO2 = (error, weak electrolyte of acetic acid, not disassembled).

(13) Chlorine reacts with water: Cl2+H2O = 2h++Cl-+ClO- (error, hypochlorous acid generated by weak electrolyte will not be disassembled).

(14) Hydrolysis reaction of sodium acetate: Ch3coo-+H3o+= Ch3cooh+H2O (Error, there are many variations on this question. Dear friends, remember that hydronium ions can be decomposed into water and hydrogen ions, so remove the water on both sides of the problem and turn it into acetic acid.

(15) Dropping aluminum chloride solution into ammonia water: Al3++4oh-= alo2-+2h2o (error, as mentioned in (9)) Dear friends, this is some test sites that ionic equation encountered in the college entrance examination in 2005-08, which I summarized. Do more exercises and summarize more.

86. In dilute solution, the heat of reaction when acid reacts with alkali to form 1 mole of water is called neutralization heat.

(1) must be a dilute solution of acid and alkali. The problem that often occurs is that concentrated sulfuric acid reacts with sodium hydroxide to generate one mole of water, which is not neutralization heat, because concentrated sulfuric acid dissolves in water and releases a lot of heat, so it must be remembered. Because concentrated acid solution and concentrated alkali solution will release heat when they are diluted with each other.

(2) Weak acid or weak base absorbs heat due to ionization in neutralization reaction, and the sum heat is less than 57.3 kJ mol-1; (3) Based on the formation of 1 mol water, when writing their thermochemical equations, the coefficient of water must be 1.

87. Combustion heat: 10 1 kPa The heat released when a pure substance is completely combusted to generate a stable oxide is called the combustion heat of the substance. The amount of (1) combustible substance is 1 mol, so when calculating the heat of combustion, the stoichiometric number of other substances in thermochemical equations often appears fractions: for example, H2 (g)+1/2o2 (g) = = H2O (l); Δ h =-285.8kj mol-1(remember that heat is directly proportional to coefficient, and if divided by 2, heat will also be divided by 2).

(2) Simple substances or compounds must be completely burned. For example, the carbon in the reactant will generate carbon dioxide instead of carbon monoxide, and the state of water is liquid and non-gaseous. When writing thermochemical equations, remember to mark the state, be optimistic about whether to write combustion heat or neutralization heat in the question, and remember the difference between neutralization heat and combustion heat clearly. Δ h =-indicates that the positive direction is exothermic reaction, and Δ h =+indicates that the positive direction is endothermic reaction (+,-must be marked and cannot be omitted). Remember that the unit should not be forgotten or misspelled.

88, light yellow AgBr, yellow AgI.

89. Why do sulfite ions react with chlorine water to produce gas? Cl2+SO3 2- +H2O=SO4 2- +2HCl, sulfite ion is incompletely reacted and reacts with reaction product hydrochloric acid to generate SO2 and SO2 gas. (So chlorine water can't react with sulfite * * *, it will be oxidized into sulfate ion, which may produce gas. )

90. Multiple-choice questions in the college entrance examination: Sulfur dioxide is introduced into acidic potassium permanganate solution, and the purple color recedes because sulfur dioxide is bleaching. (Wrong, potassium permanganate is used for strong oxidation. )

9 1, sodium test topic: the density of sodium is greater than that of potassium. So with the increase of nuclear power charge, does the density gradually increase? This is wrong.

92. Don't forget the difference method, extreme value method and conservation method when you do the sodium sub-topic. For example: (07 National Volume II) Under certain conditions, the product of the reaction of 1.5 g sodium with oxygen is dissolved in water, and the obtained solution can be neutralized with 80 mL HCl solution with a concentration of 0.50 mol/L, then the composition of the product is ().

A.Na2O

B.Na2O2

C.Na 2O and Na2O2D.

Na _ 2O _ 2 and Na _ 2O _ 2 apply the law of sodium conservation. Parents wonder if it is such a main line, sodium-sodium oxide-sodium hydroxide-sodium chloride (sodium comes from solid sodium), and the mass of sodium chloride is calculated to be 0.04 mol by the accurate and complete reaction of sodium hydroxide and hydrochloric acid. Suppose: sodium reacts with oxygen to generate sodium oxide, then sodium oxide is 0.02 mole, then the solid mass of sodium oxide is 0.02 * 62 = 1 .24g. If the products are all sodium peroxide, then the amount of sodium peroxide is 0.02 mole, and the mass is 0.02 * 78 =1.56g, because the product is/kloc.

93. Sodium is a silvery white solid, and iron is also a silvery white solid, not black. Copper is purplish red.

94, sodium bicarbonate heating object is decomposed into sodium carbonate, water, carbon dioxide.

95, the application of foam extinguisher, aluminum sulfate and sodium bicarbonate double hydrolysis, aluminum hydroxide and carbon dioxide and water.

96. Sodium reacts with acid. When sodium is left, don't forget to react with water.

97, sodium and salt solution reaction, first consider the reaction of sodium and water, then consider the reaction of sodium hydroxide and salt. For example, put sodium into copper sulfate solution.

98, observe the flame cesium reaction of potassium, through the blue cobalt glass, because potassium is mixed with sodium impurities, blue cobalt glass can filter out yellow light.

99. Prepare dilute sulfuric acid solution. Remember to inject concentrated sulfuric acid into the water and keep stirring with a glass rod. 20 1 1 Guangdong college entrance examination questions

100, three chemical equations of Hou Shi soda production method: (20 12 Jiangsu college entrance examination questions, a multiple-choice knowledge point) namely.

: sodium chloride (saturated) +NH3+H2O+CO2=

NH4Cl+NaHCO3↓2NaHCO3=

Heating = Na2CO3+H2O+CO2 =

(1) Introduce sufficient CO2 into concentrated ammonia water to generate ammonium bicarbonate.

NH3 +H2O +CO2 = NH4HCO3

(2) Add salt powder and stir.

NH4CO3+NaCl = NH4Cl+NahCO3 (precipitation)

Ammonium bicarbonate reacts with sodium chloride to form a molecule of ammonium chloride and sodium bicarbonate precipitate, and sodium bicarbonate precipitates due to low solubility.

(3) Sodium bicarbonate heats 2 nahco3 = Na2CO3+H2O+CO2 (gas)