High school chemistry optional knowledge reserve
1. Regarding whether the experimental instrument needs to be leak-detected, whether it needs to be washed, and whether it needs to be dried.
Leak detection: All plugs with plugs and glass plugs need to be leaked. For example: burettes, volumetric flasks, dispensing funnels.
Wetting: Burettes, pipettes, if not washed, will cause the concentration of the solution in the instrument to be small.
Drying: Volumetric flasks and titration-timed Erlenmeyer flasks do not need to be dried before they can be used.
2. Test center about pH test strips
(1) The accuracy of the wide-range pH test strip is an integer and cannot be accurate to the decimal point.
(2) When the pH test strip tests the pH of the solution, it cannot be wet in advance, otherwise it may cause errors.
Large (when measuring acidic solutions), small (when measuring alkaline solutions), unchanged (when measuring neutral solutions).
(3) When the pH test strip detects the acidity and alkalinity of the gas, it must be wet first and then detected.
(4) The solution with strong oxidation cannot be detected with pH test strips,
For example, the newly produced chlorine water, hypochlorite, sodium peroxide solution can not be detected with pH test strips, but can be measured with a pH meter.
3. Some test points about the measuring cylinder:
(1) The graduated cylinder does not have a zero scale value.
(2) The graduated cylinder cannot be used as a reaction vessel, nor can it be used as a container for formulating solutions.
(3) After the measuring cylinder measures the liquid into the beaker, the washing liquid cannot be poured together, otherwise it will cause a large size.
(4) The measuring cylinder, like the pallet balance, can only be accurate to 0.1.
4. On the question of whether plastic is degradable:
(1) The use of CO2 to make fully degradable plastics can reduce white pollution and reduce the greenhouse effect, but it cannot reduce acid rain.
Carbon dioxide and propylene oxide and ethylene oxide can polymerize to form degradable plastics.
(2) Lactic acid undergoes a polycondensation reaction, and the formation of polylactic acid is also degradable.
(3) Polyethylene, polyvinyl chloride and polystyrene are not degradable, and most of the polymerization products are difficult to degrade.
5. Some test points about solar energy:
(1) Light-heat conversion. Such as: mulch film, greenhouse, greenhouse, solar water heater, solar stove, solar stove.
(2) Light-heat-electricity conversion. For example, the use of solar collectors to collect heat energy into water vapor, and then drive steam turbines to generate electricity.
(3) Light-electricity direct conversion. The principle is the photoelectric effect, which directly converts solar radiation energy into light energy
The basic device is a solar cell.
(4) Light-chemical energy conversion. For example, the gain and loss of crystalline water using Na2SO4•10H2O leads to endothermic exothermic exotherm.
(5) Light-biomass energy conversion. Photosynthesis is an effective way for nature to use solar energy.
In essence, it is also photo-chemical energy conversion.
6. Biomass energy is the form of energy stored in biomass in the form of chemical energy by solar energy.
That is, the energy carried by living organisms, which is directly or indirectly derived from the photosynthesis of green plants.
7. Waste from modern agricultural production, bagasse, aquatic plants, oil plants and urban and industrial organic waste,
Animal manure, etc., biomass energy belongs to renewable resources.
8. The utilization of biomass energy includes direct combustion, biochemical conversion and thermochemical conversion.
9. The waste incineration treatment plant incinerates a large amount of domestic waste to generate electricity, converting biomass energy into heat and electricity.
10. Coal and oil are fossil fuels, not renewable energy sources. Combustible ice (natural gas) is not renewable energy.
11. Biogas can be produced by microorganisms fermenting organic matter under anaerobic conditions, so biogas is a renewable energy source.
The main component of biogas is also methane.
12. Gasoline is separated from oil and belongs to non-renewable energy sources.
13. Nuclear fuel can no longer be obtained after change, and it is not renewable energy.
14. Hydrogen energy and hydro energy are renewable energy sources。
15. The use of solar energy to decompose water to produce hydrogen with the participation of catalysts is a green chemical method that converts light energy into chemical energy.
Photolysis of water is a chemical method that does not cause pollution to green.
16. Hydrogen storage materials use chemical methods to store hydrogen gas, not physical methods.
17. Hydrogen as an energy source has three major advantages: pollution-free, high combustion value, wide range of resources,
Therefore, hydrogen is an ideal green energy source, but hydrogen has not been applied on a large scale so far.
18. Under the action of cyanobacteria, microorganisms and sunlight, the water decomposition to produce hydrogen is essentially the principle of simulating photosynthesis.
19. The test starch can be tested with iodine liquid, or iodine-potassium iodide solution, the phenomenon is that the solution turns blue.
Error-prone points:
(1) It must be carried out at room temperature, and if it is heated, it will not appear blue.
(2) Can not be carried out in an alkaline environment, iodine element will react with alkali.
(3) Potassium iodide cannot be used alone to detect.
(4) Starch can be hydrolyzed in an acidic environment, but cannot be carried out in an alkaline environment.
(5) To test whether the starch is hydrolyzed, essentially to test its hydrolysis product, so you must first add sodium hydroxide to neutralize the acid added before,
Then add the newly made copper hydroxide or silver ammonia solution and then heat it.
Note that you must first add sodium hydroxide, pay attention to first add sodium hydroxide, and pay attention to adding sodium hydroxide first.
(6) To test whether the starch is completely hydrolyzed, the essence is to test the starch itself, so the direct iodine liquid can be.
Note that sodium hydroxide must not be added, note that sodium hydroxide must not be added, and be careful not to add sodium hydroxide.
(7) to test whether halogenated hydrocarbons are hydrolyzed, essentially to test halogen ions,
So be sure to acidify it with nitric acid first, and then add silver nitrate.
20. Some error points about decentralized systems:
(1) Starch solutions and protein solutions are not really solutions, but belong to colloids.
Soy milk, soapy water, milk, and cloud smoke are all colloids that can produce the Tyndall effect.
(2) Distilled water does not belong to the dispersion system, because distilled water is pure, while the dispersion system is a mixture.
(3) The essential difference between dispersion systems is the size of the diameter
(4) Nanomaterials are not dispersed systems because they have no dispersants.
22. Silicone is a porous silicic acid dry gel obtained after drying and dehydration, and does not belong to colloids.
The use of silica gel: desiccant, adsorbent, catalyst carrier.
23. Polyethylene is a commonly used organic polymer material,
Because it is tasteless and non-toxic, it can be used to make water cups, bottles, food plastic wrap and other items in life.
Disadvantages: non-degradable, will cause white pollution.
24. More than 99% of the bromine on the earth is stored in the sea, and the total reserves of bromine in the seawater are large (not the concentration of bromine ions),
Hence the term bromine is also known as the "marine element".
25. Some test points about copper:
(1) The copper obtained by high-temperature smelting of chalcopyrite is crude copper containing a small amount of impurities,
Pure copper suitable for use in the electrical industry can be obtained by electrolysis refining.
(2) Biological copper smelting: the use of certain bacteria to convert insoluble copper salts into soluble copper salts.
Note: Copper element is not obtained directly.
(3) Because copper salts can kill some bacteria, as well as inhibit the growth of algae,
Therefore, copper sulfate can be used to treat skin diseases, gill diseases and parasites in fish.
Copper sulfate can also be used to disinfect swimming pools.
26. The density of magnesium alloy is small, the melting point is low, but the hardness and strength are larger,
Therefore, it is widely used in rockets, missiles and aircraft components.
27. Liquid oils and fats are obtained by unsaturated higher fatty acids and glycerol esterification,
After being added to hydrogen, unsaturated higher fatty acids are converted into saturated higher fatty acids, which become fat.
28. Lipids are high-grade fatty acid glycerides, but oils and fats are not polymer compounds.
29. After the oil is completely hydrolyzed in the hot sodium hydroxide solution, the resulting high-grade fatty acid sodium and glycerol can be soluble in water,
So the mixture does not stratify.
(1) Ethanol should be added before the saponification reaction begins. The role is: grease, NaOH solution can be miscible with ethanol,
The addition of ethanol allows for adequate contact between animal oil and NaOH solution, which facilitates the progression of the reaction.
(2) After the saponification reaction is completed, sodium chloride is added,
Sodium, a higher fatty acid, decreases in solubility and precipitates in the upper layer, which is glycerol in the lower layer.
(3) Ordinary esters cannot be saponified, such as ethyl acetate
Even if the reaction of higher fatty acids with ethanol is an ester, it cannot react to saponification.
(4) Oils and fats can also be hydrolyzed in an acidic environment, but it cannot be called saponification reaction.
(5) Esters can be hydrolyzed in both acidic and alkaline environments, of which hydrolysis is more thorough in alkaline environments.
Hydrolysis in an acidic environment is reversible and incomplete.
30. Some test points for amino acids:
(1) The reason why the melting point of amino acids is high is because internal salts can be produced.
(2) Glucose and amino acids can also undergo esterification reactions.
(3) Amino acids and proteins can react with both acids and bases.
(4) The simplest amino acid is glycine, and the R group is the H atom.
(5) Amino acids can undergo polycondensation reaction
31. The higher fatty acids or higher fatty acid salts produced after the hydrolysis of oils and fats belong to electrolytes.
Amino acids produced by protein hydrolysis also belong to electrolytes.
Hydrolysates of carbohydrates are not electrolytes.
32. Among nutrients, greases have the highest calorific value and can be used industrially to make soaps and paints.
33. Shea butter and sodium hydroxide undergo a hydrolytic reaction to form a mixture of sodium and glycerol of the higher fatty acids, both of which are soluble in water,
The reaction liquid is dropped into boiling water, and if there is an oily liquid floating on the surface of the water, the butter is not completely hydrolyzed.
34. About "oil" in organic matter:
(1) The grease is hydrolyzed in the caustic soda solution, and the solution is no longer delaminated. Grease belongs to the ester class, and the elemental composition is C, H, O.
(2) Mineral oil (gasoline, diesel, kerosene) does not react with caustic soda solution. Mineral oil belongs to hydrocarbons, and the elemental composition is C and H.
(3) Glycerol does not react with caustic soda solution. Glycerol belongs to the alcohol class, and the elemental composition is C, H, O.
35. Some test points about crystals:
(1) Most molecular crystals have covalent bonds, and only a small number of molecular crystals do not have chemical bonds.
For example, there are only intermolecular forces in rare gas crystals, and there is no covalent bond.
(2) Molecular crystals belonging to the electrolyte can only conduct electricity in aqueous solutions, and are not conductive in the molten state.
Such as liquid hydrogen chloride, aluminum chloride in the molten state, ferric chloride is non-conductive.
(3) Molecular crystals will destroy the intermolecular forces regardless of physical or chemical changes.
Molecular crystals break covalent bonds only when they undergo chemical reactions or dissolve in water and ionize.
For example, carbon dioxide is soluble in water, hydrogen chloride is soluble in water.
(4) Ionic crystals must have ionic bonds, and may have covalent bonds.
If you determine whether an ionic crystal has a covalent bond: see if there is a "root" in its composition
Common "roots": hydroxide, peroxide, sulfate, carbonate, bicarbonate, etc
(5) How to determine whether a compound is an ionic crystal: See if the compound can conduct electricity in the molten state.
(6) After being dissolved in water, the ionization of ions is not necessarily an ionic crystal, such as hydrogen chloride soluble in water will also produce ions.
(7) Salts are not necessarily ionic crystals, such as ferric chloride and aluminum chloride are molecular crystals.
(8) Ionic crystals do not necessarily have metallic elements, such as ammonium salts.
Supplement: Ammonium salts are decomposed by heat and do not necessarily produce ammonia, such as ammonium nitrate.
(9) Atomic crystals have and only covalent bonds, and both physical and chemical changes will destroy the covalent bonds.
Common atomic crystals are: diamond, silicon, silicon dioxide, emery, silicon nitride, aluminum nitride.
36. Judgment on the stability of molecular crystals and the height of the melting point.
Stability: Stability is a chemical property, and the stability of hydrides depends on the strength of non-metallicity,
The stronger the non-metallicity, the stronger the covalent bonds and the more stable the hydrides.
The strength of the covalent bond has nothing to do with the boiling point of the molecular crystal.
Melting point: The boiling point is a physical property, and the level of the boiling point depends on the intermolecular force.
The greater the intermolecular force, the higher the melting point of the molecular crystal.
The size of the intermolecular force is judged: first look at whether there is a hydrogen bond, if there is no hydrogen bond, it depends on the molar mass.
Example: HF is stable because the H-F bond has a large energy and has nothing to do with the hydrogen bond between molecules.
Due to the influence of hydrogen bonds, the intermolecular force of HF is greatest in the hydrides of halogenated elements.
37. Hydrogen bond: it is a special intermolecular force, but it is not a chemical bond and does not affect stability.
Hydrogen bonds only affect solubility and boiling point height.
Substances with hydrogen bonds are: ammonia, water, hydrogen fluoride, ethanol, acetic acid.
38.1mol silicon and diamond have 2NA covalent bonds.
1mol of silica and silicon carbide have 4NA covalent bonds.
1mol white phosphorus (P4) 6NA covalent bonds
The covalent bond of 39.1mol CnH2n+2 is 3n+1,
The covalent bond of 1mol CnH2n is 3n.
40. Soccerene (C60) is a closed cage-like molecule formed by 60 carbon atoms with covalent bonds,
C60 is a molecular crystal, there is an intermolecular force between the molecules, and the intermolecular force is destroyed when heated and melted.
41. Diamond is flammable in the air under high temperature conditions and cannot be used as a high temperature resistant material.
High-temperature resistant materials are generally alumina and magnesium oxide.
42. Silica, carbon dioxide, and manganese heptaoxide are all acidic oxides.
43. Although the chemical bond types of dry ice and quartz crystals are the same, the crystal types are different, and dry ice is a molecular crystal,
While quartz is an atomic crystal, dry ice needs to overcome intermolecular forces when melting, while quartz needs to overcome covalent bonds.
44. Silicon crystal melting and hydrogen iodide decomposition will destroy the covalent bond.
45. When concentrated sulfuric acid reacts with sucrose, it is first dehydrated and carbonized, and then the carbon continues to react with concentrated sulfuric acid, and the concentrated sulfuric acid oxidizes the carbon to CO2, and at the same time generates a reduction product WITH a pungent odor, SO2, and the whole process of concentrated sulfuric acid reflects dehydration and strong oxidation.
46. Green chemistry refers to the chemical industry that is pollution-free, pollution-free, and converts all the reactants into products as much as possible.
The core of green chemistry is to use chemical principles to eliminate pollution from the source, so the most significant feature of green chemistry is to convert all the reactants into products as much as possible in the process of producing chemical products, and it is not necessary to use green plants as raw materials.
47. The commonly used material of solar cells is silicon, and the principle of solar cells and primary cells is independent.
48. The energy obtained directly from nature is primary energy, and the energy obtained after processing and conversion is called secondary energy.
Geothermal, biomass, nuclear, solar, hydro, and wind are all primary energy sources.
However, electric energy, steam, gas, gasoline and diesel, heavy oil, liquefied petroleum gas, alcohol, coke, etc. are secondary energy sources.
Coal, oil and natural gas belong to primary energy, and hydrogen belongs to secondary energy.
49. Coal does not contain benzene, toluene, etc., coal is a mixture of organic macromolecules and inorganic substances.
50. The gasification of coal is the process of converting coal into combustible gases, which belongs to chemical changes;
The liquefaction of coal is the process of converting coal into liquid fuel, which belongs to chemical changes;
The dry distillation of coal is a complex chemical change process that occurs under the condition of isolating air to strengthen heat;
Fractional distillation of coal tar can give benzene, toluene, xylene, etc.
[Only the fractionation and distillation of petroleum is a physical change, the others are chemical changes]
51. The fractionation, cracking and cracking of petroleum are all important means of refining and processing petroleum, and belong to petrochemical industry.
The liquefaction of coal can obtain liquid hydrocarbons and methanol, and industrial ethylene and propylene are usually produced by petroleum cracking.
Moreover, ethylene, propylene and liquid hydrocarbons are all hydrocarbons and do not contain oxygen.
52. Petroleum cracking, also known as deep cracking, aims to obtain short-chain unsaturated hydrocarbons.
53. New energy refers to non-polluting, sustainable use of energy.
54. Common new energy sources are: solar energy, wind energy, geothermal energy, hydrogen energy, biomass energy, etc.
55. Fossil fuels are traditional energy sources, including coal, oil, and natural gas.
56. The main component of biogas is methane, but biogas is not a fossil fuel;
Water gas is a mixture of carbon monoxide and hydrogen and is not a fossil fuel;
Coke oven gas is mainly composed of hydrogen and methane, and is not a fossil fuel;
The main component of combustible ice is crystalline hydrate of methane, which belongs to fossil fuels.
57. Aromatic compounds are a class of compounds with benzene ring structure, they are structurally stable, not easy to decompose, aromatic, aromatic compounds have nothing to do with whether there is an aromatic odor.
58. Glucose contains an aldehyde group, which can produce a silver mirror after heating with a silver ammonia solution in a water bath,
A similar reaction has been used in medicine to test whether the amount of glucose in the patient's urine is too high.
59. Catalase is a protein, PVC is the English abbreviation of polyvinyl chloride (pvc is toxic),
All belong to polymer compounds; phenolic resins and plexiglass are common organic polymer compounds in life.
60. Cellulose belongs to polysaccharides, but it cannot be hydrolyzed to glucose in the human body.
61. The main component of cotton and hemp is cellulose.
Silk and wool are proteins and contain nitrogen, so burning can produce nitrogen oxides.
62. The main components of degreasing cotton and filter paper are cellulose, and the final product of cellulose hydrolysis is glucose.
63. Polyethylene and cotton cloth are completely burned to produce carbon dioxide and water,
Wool is mainly composed of protein, which contains C, H, O, N and other elements.
In addition to carbon dioxide and water, the products produced by the complete combustion of wool also contain nitrogen-containing compounds.
64. Ethanol is used for disinfection, formalin is used for leaching specimens,
It is because ethanol and formaldehyde can denature proteins and kill germs, and the principles of the two are the same.
65. ClO2 has strong oxidation and can be used for sterilization and disinfection of drinking water.
66. Bromomethane has been widely used as a pesticide for smoked land,
Bromine compounds can be used as flame retardants, water purifiers, pesticides, dyes and the like.
67. Crystalline bovine insulin synthesized in China is protein.
68. After the washing operation is completed after the filtration is completed, the small tap should be turned off and water (or detergent such as alcohol lamps) should be added to the Brinell funnel.
Until immersion pellet, wait for the detergent to flow slowly, repeat the operation 2-3 times.
69. When the crystal is transferred into the Brinell funnel, there are crystals sticking to the cup wall, in order to avoid the loss of the crystals dissolved, rinse with filtrate.
70. After the extraction is completed, the rubber tube connecting the safety bottle and the suction device should be disconnected first, and then the faucet in the pumping device should be closed.
71. When decompression filtration, when the filtrate in the suction filter bottle is close to the branch mouth, the rubber tube should be removed to pour the filtrate out of the upper mouth of the suction filter bottle; 72. The decompression filter has the advantages of fast filtration speed and drier solids.
73. Substances with colloids and small particles cannot be filtered by reduced pressure; decompression filtration can be used when heat filtration.
74. The preparation of metal Mg is to be melted by electrolysis of MgCl2.
Magnesium oxide has a high melting point and can be used as a high-temperature resistant material, such as refractory bricks, refractory tubes, etc.
Magnesium alloys have a small density and cannot be used to manufacture major components of heavy machinery.
Magnesium is ignited in the air, burns violently, emits a dazzling white light, emits a large amount of heat, and generates a white solid magnesium oxide,
Magnesium can be used to make flares, fireworks, glitter powder, etc.
75. Graphite, diamond, nanocarbon tubes and C60 are all all isotropes of carbon.
76. The filtration experiment should not be stirred on the filter with a glass rod to prevent damage to the filter paper and cause the filtration to fail.
77. The excess sodium in the experiment should be put back into the original bottle of kerosene in time for preservation.
78. Metals or metal cations can be determined by flame color reaction.
79. There are two places for leak detection in the separating funnel, namely the stopper and the piston, and the volumetric flask needs to oscillate upside down when preparing the solution,
Therefore, leak detection should be carried out before use.
80. The volume of liquid contained in the separating funnel shall not exceed 3/4 of its volume.
When deflating after slowly shaking the separating funnel, the lower mouth of the funnel should be slightly tilted upwards, and then the funnel plug should be opened for deflation, and the funnel neck cannot be facing the person or the open flame source when deflating.
81. The volumetric flask is an instrument for preparing a solution of a certain amount of substance, and cannot be used as a container for the reaction and dissolution of substances.
82. Platinum wire or wire has a high melting point and the flame is colorless when burning, so it can be used for flame reaction experiments.
83. The chemical formula of raw gypsum is CaSO4•2H2O, and the chemical formula of wrought gypsum is 2CaSO4•H2O.
84. The first step of the principle of limestone-gypsum desulfurization is: SO2 + Ca(OH)2
CaSO3 ＋ H2O，
The product is then oxidized to make a gypsum: 2CaSO3 +O2
2CaSO4 。
85. Industrial aluminum method (write out the ion equation)
(1) Bauxite mixed with sodium hydroxide solution: Al2O3 + 2OH—
2AlO2—＋ H2O。
(2) In the filtered filtrate, excess CO2 gas is injected: AlO2-+2H2O+CO2
Al(OH)3↓+ HCO3—
(3) Precipitate Al(OH)3 and burn: 2Al(OH)3 △Al2O3+ 3H2O.
(4) Electrolytic molten alumina: 2Al2O3
4Al + 3O2↑。
86. Extraction of magnesium from seawater:
(1) First calcinate a large amount of shells on the seashore into quicklime, and make quicklime into lime milk:
CaCO3 high temperature (=====) CaO + CO2↑ , CaO + H2O
Ca(OH)2 。
(2) The factory for refining magnesium should be built on the seashore, and the lime milk is added to the sedimentation tank and filtered to obtain Mg(OH)2 precipitation;
MgCl2 ＋ Ca(OH)2
Mg(OH)2 ↓＋ CaCl2 。
(3) Mg(OH)2 was reacted with hydrochloric acid to cool down the crystallization to obtain magnesium chloride;
Mg(OH)2 ＋2HCl
MgCl2＋ H2O。
(4) Magnesium chloride hexahydrate was heated in an atmosphere of HCl to give anhydrous magnesium chloride: .
(5) Electrolytically melted magnesium chloride, you can get magnesium metal and chlorine gas,
MgCl2
Mg ＋ Cl2 ↑。
87. Bromine extraction from seawater
(1) First use the distillation method to concentrate the seawater, and then use sulfuric acid to acidify the concentrated seawater.
An appropriate amount of chlorine gas is introduced into the acidified seawater to convert the bromine ions into bromine elements.
2NaBr + Cl2
Br2 ＋ 2NaCl
(2) blowing bromine vapor into an aqueous solution containing bromine elements into the aqueous solution of bromine or water vapor,
The bromine element is passed into the absorption column containing sulfur dioxide solution to achieve the purpose of enrichment.
Br2 ＋ SO2 ＋ H2O
2HBr ＋ H2SO4
(3) inject an appropriate amount of chlorine into the solution in the absorption tower,
2HBr＋ Cl2
Br2 ＋ 2HCl
(4) Use carbon tetrachloride (or benzene) to extract bromine element in the solution in the absorption tower.
88. Iodine is extracted from seawater, although the total reserve of iodine in seawater is very large, but because of its low concentration,
Therefore, the current acquisition of iodine in industrial production is not directly extracted from seawater.
Because some plants in the ocean have the ability to enrich iodine, such as kelp, etc.,
Therefore, the extraction of iodine from seafood such as kelp is an important way to obtain iodine industrially.
The flowchart for extracting iodine from kelp is as follows:
89. The main ingredient of barium meals commonly used in hospitals is barium sulfate.
90. The gases that can spontaneously combust in air are generally PH3 and SiH4.
91. The nature of sodium is very active, and it can replace titanium, zirconium, niobium and other metals from the molten chloride of titanium, zirconium, niobium and other metals.
92. Silver bromide is an important photosensitive material and an indispensable component in film.
93. Silver iodide can make the water vapor in the air accumulate to form water droplets, which can be used for artificial rainfall.
94. Infrared spectrometer can be used to determine the group and chemical bond composition in the molecular structure of organic matter.
95. At room temperature, liquid chlorine does not react with iron, so it can be stored in steel cylinders.
96. Test points about silicates:
The raw materials for the manufacture of ordinary glass are soda ash, limestone and quartz, equipment: glass furnace
The raw materials for the manufacture of ordinary cement are: limestone, clay (aluminosilicate), gypsum, equipment: cement rotary kiln.
Common silicate products: ceramics, bricks, glass, cement, molecular sieves.
(1) The aqueous solution of sodium silicate is called water glass, and water glass is not glass.
(2) The use of sodium silicate: to make wood, textile fire agent, preservative, construction industry adhesive.
(3) Plexiglass is not a silicate and belongs to organic matter.
(5) The use of molecular sieves: mixtures for separating and purifying gases or liquids, desiccants, ion exchangers,
Catalysts and catalyst carriers.
97. Sodium sulfate is combined with hydration to form glauber's salt, this reaction is exothermic, and glauber's salt is decomposed by heat to form sodium sulfate and water, and this reaction absorbs heat.
98. When preparing ferric chloride solution, iron chloride can be dissolved in a stronger hydrochloric acid,
Then dilute with water to inhibit hydrolysis of ferric chloride.
NH3 is reducible and can reduce nitrogen oxides to N2, so NH3 can be used to remove flue gas.
Ammonia can also reduce copper oxide and iron oxide.
99. The substances in which free states exist in nature are: iron, copper, sulfur, oxygen, nitrogen, and noble gases.
Silicon does not exist in a free state in nature, but generally exists in the form of silicon oxides and silicates.
100. (1) Fe2 + in contact with potassium ferrocyanide (K3 [Fe(CN)6]) solution to generate a blue precipitate (Teng's blue precipitate).
(2) Fe3 + met with potassium ferrocyanide (K4 [Fe(CN)6]) solution to generate a blue precipitate (Prussian blue precipitate).
(3) Check Fe3+: Add KSCN to see if the solution turns blood red. (Note that it does not become a precipitate)
(4) Test Fe2+: first add KSCN, and then add an appropriate amount of chlorine or hydrogen peroxide to see if it turns red.
(5) Check whether Fe3+ is mixed with Fe2+: add acidic potassium permanganate solution to see if it fades.
If there are chloride ions in the solution, this method cannot be used.
11. Add ammonia drop by drop, there will be precipitation, continue to add ammonia dropwise, the precipitation will disappear,
There may be Ag+, Cu2+, in that solution,
Process: First form silver hydroxide, copper hydroxide, and then form silver ammonia solution, cupra solution.