Common Names Scientific Names Chemical Formulas
Diamond, Graphite C
Alcohol Ethanol C2H5OH
Slaked Lime, Slippery Lime Calcium hydroxide Calcium hydroxide Ca(OH)2
Lime Calcium Oxide CaO
Acetic Acid (melting point 16.6°C, the solid state is known as Glacial Acetic Acid ) Acetic acid CH3COOH
Wood alcohol, wood alcohol Methanol CH3OH
Dry ice Solid CO2 CO2
Copper green, malachite Alkaline copper carbonate Cu2(OH)2CO3
Cholestones, blue alum Copper sulphate crystals CuSO4-5H2O
Hydrogen sulphuric acid H2S
Sulphite H2SO3
Salt acid water (industrial name) Hydrochloric acid, hydrochloric acid HCl
Mercury Mercury Hg
Soda ash, soda, soda ash Sodium carbonate Na2CO3
Soda ash crystals Sodium carbonate crystals Na2CO3-10H2O
Acidic sodium carbonate, baking soda Sodium bicarbonate NaHCO3
Caustic soda , caustic soda, caustic soda Sodium hydroxide NaOH
Toxic salt, nitrate salt (industrial name) Sodium nitrite NaNO2
Ammonia monohydrate Ammonia NH3-H2O
2, the color and state of common substances
1, white solids: MgO, P2O5, CaO, NaOH, Ca(OH)2, KClO3, KCl, Na2CO3, NaCl, anhydrous CuSO4; iron, magnesium is silver-white (mercury is silver-white liquid)
2, black solids: graphite, charcoal powder, iron powder, CuO, MnO2, Fe3O4, * KMnO4 is violet-black
3, red solids: Cu, Fe2O3 , HgO, red phosphorus
4, yellowish: sulfur.
5, green: Cu2(OH)2CO3 is green
6, the color of the solution: any solution containing Cu2+ blue; any solution containing Fe2+ light green; any solution containing Fe3+ brownish-yellow, the rest of the solution is generally colorless. (Potassium permanganate solution is purple-red)
7, precipitation (that is, insoluble in water salt and alkali): ① salt: white ↓: CaCO3, BaCO3 (dissolved in acid) AgCl, BaSO4 (also insoluble in dilute HNO3), etc. ② alkali: blue precipitate: Cu (OH) 2; reddish-brown precipitate: Fe (OH) 3, white precipitate: the rest of the alkali.
8, (1) gases with irritating gases: NH3, SO2, HCl (all colorless)
(2) colorless and odorless gases: O2, H2, N2, CO2, CH4, CO (highly toxic)
Note: liquids with irritating odors: hydrochloric acid, nitric acid, acetic acid. Alcohol is a liquid with a special gas.
9, toxic, gas: CO Liquid: CH3OH Solid: NaNO2, CuSO4 (can be used as a fungicide ,mixed with slaked lime to form a sky-blue sticky substance - Bordeaux liquid).
Three, the solubility of substances
1, the solubility of salt
Substances containing potassium, sodium, nitrate, ammonium are soluble in water
Cl-containing compounds are only AgCl and HgCl do not dissolve in water, the others are soluble in water;
SO42-containing compounds are only BaSO4 , PbSO4 not soluble in water. PbSO4 is insoluble in water, AgSO4 is slightly soluble in water, the others are soluble in water.
Only CO32-containing substances K2CO3, Na2CO3, (NH4)2CO3 is soluble in water, the others are insoluble in water
2, the solubility of alkali
Water-soluble alkali: barium hydroxide, potassium hydroxide, calcium hydroxide, sodium hydroxide, and ammonia, the other alkali insoluble in water. Refractory bases in Fe (OH) 3 is a reddish-brown precipitate, Cu (OH) 2 is a blue precipitate, other refractory bases are white. (Including Fe(OH)2)
Note: AgCl and BaSO4 are insoluble in dilute nitric acid, other precipitates are soluble in acid. For example: Mg(OH)2 CaCO3 BaCO3. and so on.
3, most acids and acidic oxides soluble in water, (acidic oxides + water → acid) most basic oxides are insoluble in water, soluble: barium oxide, potassium oxide, calcium oxide, sodium oxide (basic oxides + water → alkali). There is a mnemonic to help students memorize these things: potassium, sodium, ammonium and nitrate are soluble, hydrochloric acid insoluble silver mercury; sulfate insoluble barium and lead, carbon phosphate insoluble; most acid soluble alkali soluble, only potassium, sodium, ammonium and barium soluble.
Four, the most chemical
1, the most abundant metal element in the earth's crust is aluminum.
2, the most abundant non-metallic element in the earth's crust is oxygen.
3. The most abundant substance in the air is nitrogen.
4. The hardest naturally occurring substance is diamond.
5. The simplest organic substance is methane.
6. The most active metal in the order of activity table of metals is potassium.
7. The oxide with the smallest relative molecular mass is water.
8. The simplest organic compound is CH4.
9. The least dense gas under the same conditions is hydrogen.
10. The most conductive metal is silver.
11. The atom with the smallest relative atomic mass is hydrogen.
12. The metal with the lowest melting point is mercury.
13. The most abundant element in the human body is oxygen.
14. The element that makes up the largest variety of compounds is carbon.
15、The most widely used metal in daily life is iron.
16, the only non-metallic liquid monomers is bromine;
17, the earliest use of natural gas is China;
18, China's largest coal base in: Shanxi province;
19, the earliest use of wet refining of copper is China (Western Han Dynasty discovery [Liu An, "Huainan Wannbijie" "Zeng Qing get iron then turned into copper " ], Song Dynasty application);
20, the first to discover the electron is the British Thomson;
21, the first to conclude that the air is composed of N2 and O2 is the French Lavoisier.
V. Chemistry in the "certain" and "not necessarily"
1, chemical changes must have physical changes, physical changes do not necessarily have chemical changes.
2, the metal at room temperature are not necessarily solid (such as Hg is liquid), non-metals are not necessarily gas or solid (such as Br2 is liquid) Note: metal, non-metal refers to the monomers, not to be confused with the constituent elements of matter.
3, the atomic group must be charged ions, but the atomic group is not necessarily acid (such as NH4 +, OH-); acid is not necessarily an atomic group (such as Cl- called hydrochloric acid).
4, slow oxidation does not necessarily cause spontaneous combustion. Combustion is necessarily a chemical change. Explosion is not necessarily a chemical change. (For example, a pressure cooker explosion is a physical change.)
5, the nucleus of an atom does not always have neutrons (such as H atoms have no neutrons).
6, atoms are not necessarily smaller than molecules (can not say "molecules big, small atoms"). The fundamental difference between molecules and atoms is that in chemical reactions molecules are separable and atoms are not.
7, substances composed of the same element are not necessarily monomers, but may also be a mixture of several monomers. Such as O2 and O3.
8, the outermost electron number of 8 particles are not necessarily atoms of rare gas elements, but may also be cations or anions.
9, the number of electrons in the outermost layer of an atom with a stable structure is not necessarily 8, such as helium atoms. (The first layer is the outermost 2 electrons).
10, Particles with the same nuclear charge are not necessarily the same element. (Because particles include atoms, molecules, ions, and elements do not include molecules or clusters of atoms made up of multiple atoms.) Only single-nucleated particles (one atom, one nucleus) with the same nuclear charge must belong to the same element.
11, (1) A concentrated solution is not necessarily a saturated solution; 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 not determined, as the temperature must be.) (3) A solution after crystals have been precipitated must be a saturated solution of a substance. A saturated solution does not necessarily precipitate crystals when the temperature is lowered. (4) The solubility of any substance at a given temperature must be greater than the mass fraction of solute in its saturated solution, i.e., S must be greater than C .
12, there are monomers and compounds to participate in or generate the reaction, is not necessarily a replacement reaction. But there must be a change in the valency of the elements.
13, decomposition and chemical reactions do not necessarily have a change in elemental valence; replacement reactions must have a change in elemental valence; complex decomposition reactions must not have a change in elemental valence. (Note: redox reactions, there must be a change in the valency of the elements)
14, monomers must not undergo decomposition reactions.
15, the same element in the same compound does not necessarily show a valence. For example, NH4NO3 (the front N is -3 valence, the back N is +5 valence)
16, salt does not necessarily have a metal element in its composition, for example, NH4+ is a cation and has the properties of a metal ion, but is not a metal ion.
17, cations are not necessarily metal ions. Such as H+ , NH4+ .
18, in the composition of compounds (oxides, acids, bases, salts), must contain the element of oxygen are oxides and bases; not necessarily (possibly) oxygen-containing elements are acids and salts; must contain the element of hydrogen are acids and bases; not necessarily hydrogen-containing elements are salts and oxides; salts and bases do not necessarily contain the metal element in the composition of the salt, (eg, NH4NO3, NH3, H2O); the composition of acids may contain Metal elements may be present in the composition of acids (e.g., HMnO4 is called permanganate), but non-metal elements must be present in the composition of all substances.
19, salt solutions are not necessarily neutral. For example, Na2CO3 solution is alkaline.
20, solutions of acid salts are not necessarily acidic (that is, PH is not necessarily less than 7), such as NaHCO3 solution is alkaline. But a solution of sodium bisulfate is acidic, so a substance that ionizes hydrogen ions is not necessarily an acid.
21, acid solution must be acidic solution, but acidic solution is not necessarily acid solution, such as: H2SO4, NaHSO4 solution are acidic, and NaHSO4 salt. (Acid solution is an aqueous solution of acid, acidic solution is a solution containing H+).
22, alkali solution must be alkaline solution, but alkaline solution is not necessarily alkaline solution. For example: NaOH, Na2CO3, NaHCO3 solution are alkaline, and Na2CO3, NaHCO3 for salt. (An alkaline solution is an aqueous solution of a base, and an alkaline solution is a solution containing OH-).
23, basic oxides must be metal oxides, metal oxides are not necessarily basic oxides. (e.g. Mn2O7 is a metal oxide, but it is an acid oxide, and its corresponding acid is permanganate, or HMnO4); remember: of the alkaline oxides, only K2O, Na2O, BaO, and CaO are soluble in water and react with water to form bases.
24, acidic oxides are not necessarily non-metallic oxides (such as Mn2O7 ), non-metallic oxides are not necessarily acidic oxides (such as H2O, CO, NO). ★ common acidic oxides: CO2, SO2, SO3, P2O5, SiO2, etc., most of the acidic oxides can dissolve in water and react with water to produce the corresponding acid, remember that silicon dioxide (SiO2) is not soluble in water.
25, the reaction that produces salt and water is not necessarily a neutralization reaction.
26, all chemical reactions do not necessarily belong to the basic reaction type, not a basic reaction: ① CO and metal oxides reaction; ② acidic oxides and alkali reaction; ③ organic combustion.
27, where the monomorphic iron to participate in the replacement reaction (iron and acid, salt reaction), after the reaction of iron must show +2 (that is, the generation of ferrous salts).
28, where the metal and acid replacement reaction, the reaction must increase the mass of the solution. Where the metal reacts with the salt solution, to determine the reaction before and after the change in the mass of the solution, just look at the size of the relative atomic mass of the metal to participate in the reaction and the size of the relative atomic mass of the metal generated. "Big for small weight gain, small for big weight loss" .
29, where the same mass of the same valence state of the metal and acid reaction, the greater the relative atomic mass of the hydrogen produced by the mass of the less.
30, where the metal can react with water at room temperature (such as K, Ca, Na), it must not be able to salt solution replacement reaction; but they react with the acid is the most intense. Such as Na added to the CuSO4 solution, the reaction is: 2Na + 2H2O = 2NaOH + H2 ↑; 2NaOH + CuSO4 = Cu (OH) 2 ↓ + Na2SO4.
31, any air-exhaustion method (either upward or downward), be sure to extend the guide tube to the bottom of the collection cylinder.
32, the generating device for preparing gases must be checked for airtightness before filling it with drugs. Always check the purity of a flammable gas before igniting or heating it .
33, when writing chemical formulas, positive elements are not always written on the left. Such as NH3 , CH4.
34, 5g of a substance into 95g of water, fully dissolved, the resulting solution is not necessarily equal to 5% solute mass fraction.
It may be equal to 5%, such as NaCl, KNO3, etc.; it may be greater than 5%, such as K2O, Na2O, BaO, SO3, etc.; it may be less than 5%, such as the crystalline hydrate and Ca(OH)2 , CaO, etc..
◆ Under the same conditions, CaO or Ca(OH)2 dissolved in water to obtain the solution of the smallest mass fraction of solute
Sixth, junior high school chemistry in the "three"
1, the composition of the three kinds of particles of matter are molecules, atoms, ions.
2, reduce copper oxide commonly used three reducing agents hydrogen, carbon monoxide, carbon.
3, hydrogen as a fuel has three major advantages: abundant resources, high heat generation, the product of combustion is water does not pollute the environment.
4, the composition of the atom generally have three kinds of particles: protons, neutrons, electrons.
5, there are only three ferrous metals: iron, manganese, chromium.
6, the elements that make up matter can be divided into three categories namely (1) metallic elements, (2) non-metallic elements, (3) rare gas elements.
7, There are three types of iron oxides which have the chemical formulas (1) FeO, (2) Fe2O3, and (3) Fe3O4.
8, There are three characteristics of solutions (1) homogeneity, (2) stability, and (3) mixtures.
9, chemical equations have three meanings: (1) that what substances to participate in the reaction, the result of what substances; (2) that the reactants, products of each substance asked the molecules or atoms of the number of particles than; (3) that the reactants, the products of the mass ratio between. Chemical equations have two principles: based on objective facts; follow the law of conservation of mass.
10, pig iron is generally divided into three kinds: white iron, gray iron, ductile iron.
11, carbon steel can be divided into three kinds: high carbon steel, medium carbon steel, low carbon steel.
12, commonly used in ironmaking iron ore there are three kinds: (1) hematite (the main component of Fe2O3); (2) magnetite (Fe3O4); (3) rhodonite (FeCO3).
13, there are three main equipment for steelmaking: converter, electric furnace, flat furnace.
14, the three reaction conditions often associated with temperature are ignition, heating, and high temperature.
15, saturated solution into an unsaturated solution there are two ways: (1) warming, (2) add solvent; unsaturated solution into a saturated solution there are three ways: lowering the temperature, add solute, constant temperature evaporation of solvent. (Note: solubility with temperature and become smaller substances such as: calcium hydroxide solution from a saturated solution into an unsaturated solution: lower the temperature, add solvent ...) .
16, there are generally three ways to collect gases: drainage method, upward air exhaust method, downward air exhaust method.
17, the three main causes of water pollution: (1) industrial production of waste residue, waste gas, waste water; (2) the arbitrary discharge of domestic sewage; (3) agricultural production of pesticides and fertilizers applied with rainwater into the river.
18, there are three kinds of fire extinguishers usually used: foam fire extinguishers; dry powder fire extinguishers; liquid carbon dioxide fire extinguishers.
19, the solubility of solid substances with the change in temperature can be divided into three categories: (1) most solid substances solubility increases with the increase in temperature; (2) a few substances solubility by the temperature is very small; (3) very few substances solubility decreases with the increase in temperature.
20, CO2 can extinguish fires for three reasons: it cannot burn, it cannot support combustion, and it is denser than air.
21, monomers can be divided into three categories: metal monomers; nonmetal monomers; rare gas monomers.
22, the three most important fossil fuels in the world today are: coal, oil, natural gas.
23, the three black oxides that should be remembered are: copper oxide, manganese dioxide, and iron tetraoxide.
24, hydrogen and carbon monomers have three similar chemical properties: stability at room temperature, flammability, and reducibility.
25, three pale blue color appearing in the textbook: (1) liquid oxygen is pale blue (2) sulfur burns in air with a faint pale blue flame, (3) hydrogen burns in air with a pale blue flame.
26, three blue colors associated with the element copper: (1) copper sulfate crystals; (2) copper hydroxide precipitate; (3) copper sulfate solution.
27, filtration operation in the "three against": (1) the lower end of the funnel against the inner wall of the beaker; (2) the end of the glass rod lightly against the three layers of filter paper; (3) the beaker to be filtered against the rim of the beaker to be cupped in the glass to divert the flow.
28, the three major gaseous pollutants: SO2, CO, NO2.
29, the flame of the alcohol lamp is divided into three parts: the outer flame, the inner flame, the center of the flame, of which the outer flame has the highest temperature.
30, access to medicines have "three not" principle: (1) without hands touching the drugs; (2) do not put your nose to the mouth of the container to smell the odor of the gas; (3) do not taste the flavor of the drugs.
31, the three major chemical processes in ancient times: papermaking, gunpowder making and porcelain burning.
32, the three industrial wastes: waste water, waste residue, exhaust .
33, three instruments that can be directly heated: test tubes, crucibles, evaporating dishes (in addition to the burning spoon).
34, the conservation of mass explains the atomic three invariant: the species does not change, the number does not increase or decrease, the mass does not change.
35, and air mixed with the ignition of three gases may explode: H2, CO, CH4 (actually any flammable gas and dust).
36, three main products of coal dry distillation (chemical change): coke, coal tar, coke oven gas.
37, concentrated sulfuric acid three properties: water absorption, dehydration, strong oxidizing.
38, the use of alcohol lamps three prohibitions: to the burning, to the lit lamp with alcohol, mouth blow out.
39, the three steps of solution preparation: calculation, weighing (measure), dissolve.
40, the top three most abundant elements in living cells: O, C, H .
41, three equations in the atom: nuclear charge = number of protons = number of electrons outside the nucleus = atomic number .
Seven, the order of metal activity:
Metal activity order from strong to weak: K Ca Na Mg Al Zn Fe Sn Pb (H) Cu Hg Ag Pt Au
(recite in order) potassium calcium sodium magnesium aluminum zinc iron tin lead (hydrogen) copper mercury silver platinum
One of the order of metal activity mnemonic: Jagai Na Mei donkey, new hooves like to lead light, the unified ***Hundred pounds
Meaning: There is a beautiful donkey named Jagai, with new hooves, he likes to carry light goods. statistics, only 100 pounds
① metal position more in front of the more active, the more likely to lose electrons to ions, the faster the reaction rate
② in front of the hydrogen in the metal can replace the hydrogen in the acid, lined up after the hydrogen in the metal can not replace the hydrogen in the acid, with the acid does not react;
3 in front of the metal, the metal in the back of the row of the metal from the salt solution to replace them. (c) The metal in front can displace the metal behind it from its salt solution. The metal in the back does not react with the salt solution of the metal in the front.
4 mixed salt solution and a metal in the order of replacement reaction is "first far" "after close"
Note: * monomorphic iron in the replacement reaction is always changed to +2 valence of ferrous
VIII, metal + acid → salt ＋ H2 ↑ in:
VIII, metal + acid → salt ＋ H2 ↑ in:
VII. H2 ↑ in:
① equal mass of metal and the reaction of sufficient acid, the release of hydrogen from the order of more or less: Al>Mg>Fe>Zn.
② equal mass of different acids and the reaction of sufficient metal, the smaller the relative molecular mass of the acid the more hydrogen is released.
3) When equal masses of the same acid react with sufficient quantities of different metals, the same amount of hydrogen is released.
3, the test of substances
(1) acid (H +) test.
Method 1 Drop a drop of purple litmus into a test tube containing a small amount of the liquid to be tested, oscillate, and if the litmus turns red, it proves that H+ is present.
Method 2 Dip a dry clean glass rod into a drop of the unknown liquid on blue litmus paper, if the blue paper turns red, the presence of H+ is proved.
Method 3 Dip a dry clean glass rod into a drop of the unknown liquid on pH test paper, then compare the color of the test paper with the standard colorimetric card to know the pH of the solution, and if the pH is less than 7, it proves the presence of H+.
(2) Silver salt (Ag+) test.
Pour a small amount of hydrochloric acid or a small amount of soluble hydrochloric acid solution into a test tube containing a small amount of the liquid to be measured, oscillation, if there is a white precipitate, and then add a small amount of dilute nitric acid, if the precipitate does not disappear, then the existence of Ag+ is proved.
(3) Test for alkali (OH-).
Method 1 Drops of purple litmus solution into a test tube containing a small amount of the liquid to be tested, oscillate, and if the litmus solution turns blue, the presence of OH- is proved.
Method 2 Dip a dry, clean glass rod into a drop of the unknown liquid on red litmus paper, if the red litmus paper turns blue, the presence of OH- is proved.
Method 3 Drop colorless phenolphthalein test solution into a test tube containing a small amount of the liquid to be tested, oscillate and if the phenolphthalein test solution turns red, the presence of OH- is proved.
Method 4 Dip a dry, clean glass rod into a drop of the unknown solution on pH test paper, and then compare the color shown on the paper with the standard colorimetric card to know the pH of the solution, and if the pH is greater than 7, it proves the presence of OH-.
(4) Test for chloride or hydrochloride or hydrochloric acid (Cl-).
Pour a small amount of silver nitrate solution into a test tube containing a small amount of the liquid to be tested, oscillate, and if a white precipitate is produced, add a small amount of dilute nitric acid, and if the precipitate does not disappear, the presence of Cl- is proved.
(5) Test for sulfate or sulfuric acid (SO42-).
Pour a small amount of barium chloride solution or barium nitrate solution into a test tube containing a small amount of the liquid to be measured, oscillate, if there is a white precipitate, then add a small amount of dilute nitric acid, if the precipitate does not disappear, it proves that the presence of SO42-.
(6) Test for CO32- or HCO3-.
Pour a small amount of hydrochloric acid or nitric acid into a test tube containing a small amount of material to be measured, if there is a colorless gas released, the gas will be passed into a test tube containing a small amount of clarified lime water, if the lime water becomes muddy, it proves that the original material to be measured in the presence of CO32- or HCO3-.
＊SO42- and Cl- exist at the same time, if you want to test, you must first use Ba (NO3) 2 solution to test and remove SO42-, and then use AgNO3 solution to test Cl-, because if you first add AgNO3, AgNO3 and SO42- reaction to produce AgSO4 is a microsoluble material, and therefore can not distinguish between Cl- or SO42-. Ba(NO3)2 must be used here; if BaCl2 is used, Cl- is introduced.
(6) Ammonium salt (NH4+):
A concentrated NaOH solution (slightly hot) is used to produce a gas that turns wet red litmus paper blue.
IX, metal + salt solution → new metal + new salt in:
①When the relative atomic mass of the metal > the relative atomic mass of the new metal, the mass of the solution becomes heavier and the metal lighter after the reaction.
② When the relative atomic mass of the metal < the relative atomic mass of the new metal, the mass of the solution becomes lighter and the metal becomes heavier after the reaction.
③After the reaction metal + acid → salt + H2↑, the mass of the solution becomes heavier and the metal becomes lighter.
Ten, material combustion factors:
① oxygen concentration is different, the product is also different. For example, carbon dioxide is generated when there is enough oxygen, and carbon monoxide is generated when there is not enough.
② different concentrations of oxygen, the phenomenon is different. For example: sulfur combustion in air is a light blue flame, in pure oxygen is a blue flame.
③The concentration of oxygen is different, the degree of reaction is also different. For example, iron burns in pure oxygen, but not in air.
4) The degree of combustion is different depending on the contact area of the substance. E.g., burning of briquettes and burning of honeycomb coal.
XI. Factors affecting the dissolution of substances:
①Stirring or oscillation. Stirring or oscillation can speed up the rate of dissolution of substances.
② warming. Elevated temperature can accelerate the rate of dissolution of substances.
③Solvent. The solvent chosen for the solubility of different substances is also different.
Twelve, the law of the periodic table:
① the same number of elements in the same period of the same number of electronic layers, from left to right, the number of nuclear charge, the number of protons, the number of electrons outside the nucleus in increasing order.
② the same number of electrons outside the nucleus of the elements in the same group, the chemical properties of the elements are similar, from top to bottom of the number of nuclear charges, the number of protons, the number of electron layers in increasing order.
Thirteen, the atomic structure of the knowledge of the eight determinants of the relationship:
① proton number determines the number of charges carried by the nucleus of the atom (nuclear charge)
Because the number of protons in the atom = nuclear charge.
②The number of protons determines the type of element.
3) The number of protons and neutrons determines the relative atomic mass of an atom.
Because number of protons + number of neutrons in an atom = relative atomic mass of the atom.
④The level of electron energy determines the distance of the region of electron motion from the nucleus.
Because the closer to the nucleus, the lower the energy of the electron, and the farther away, the higher the energy.
5 The number of electrons in the outermost layer of an atom determines the class of the element.
Because the number of electrons in the outermost layer of an atom <4 is a metal, > or =4 is a nonmetal, and =8 (=2 when the first layer is the outermost) is a rare gas element.
6 The number of electrons in the outermost layer of an atom determines the chemical properties of an element. Because the number of electrons in the outermost layer of an atom <4 is loss of electrons, > or =4 is gain of electrons, and =8 (=2 when the first layer is the outermost layer) is stable.
7 The number of electrons in the outermost layer of an atom determines the valency of the element.
An atom loses electrons and the element shows a positive valence, while an atom gains electrons and the element shows a negative valence, and the value of the valence = the number of electrons gained or lost.
⑧ atomic outermost layer of the number of electrons to determine the number of charges carried by ions
atomic loss of electrons for the cation, gained electrons for the anion, the number of charges = the number of lost electrons
XIV, junior high school chemistry experiments in the "first" and "after "
①Tray balance: use the tray balance, the first to adjust the balance. When adjusting the balance, first move the tourniquet to zero scale, and then turn the balance nut to reach equilibrium.
②Heating: when using test tubes or flasks to heat the drugs, first preheat, and then focus on heating.
③ gas production: gas production, you must first check the gas tightness of the device, and then fill the drug.
④ Mixing of solids and liquids: when mixing or reacting solids and liquids with each other, the solids must be added first, then the liquids.
⑤ Testing flammable gases: When testing the flammability of hydrogen and other gases, the purity of the hydrogen and other gases should be tested first, and then its flammability and other properties should be tested.
6 Redox reactions: when reducing solid substances such as copper oxide with reducing gases (e.g., H2, CO), heat is generally required. When experimenting, pass the gas for a while, then heat it up. After the experiment, continue to pass hydrogen gas, first remove the alcohol lamp until the test tube cools, then remove the gas guide.
7 Dilution of concentrated sulfuric acid: to dilute concentrated sulfuric acid, first add distilled water to the beaker, then slowly inject concentrated sulfuric acid along the wall of the beaker, and use a glass rod to constantly stir, and then bottle after cooling.
8 separation of mixtures: separation of salt and potassium nitrate mixture by recrystallization, when the salt accounts for a considerable amount, you can first heat the evaporation of saturated solution, precipitation of salt crystals, filtration, and then cool the mother liquor precipitation of potassium nitrate crystals; when the potassium nitrate accounted for a considerable amount, you can first cool the hot saturated solution, potassium nitrate crystals, filtration, and then evaporation of the mother liquor, precipitation of salt crystals.
9 neutralization titration: in the experiment of neutralization titration, the solution to be tested is generally selected alkali solution, should be added to the solution to be tested phenolphthalein reagent, so that the red, and then add the acid solution drop by drop, stirring, until the red color is just right to retreat.
⑩Removal of carbon dioxide and water vapor in a mixture of gases: to remove carbon dioxide and water vapor in a mixture of gases, the gas mixture should be passed through a washer bottle containing a concentrated sodium hydroxide solution first, and then followed by a washer bottle containing concentrated sulfuric acid.
(12) Test for the presence of carbon dioxide and water vapor in a gas mixture: in testing for the presence of carbon dioxide and water vapor in a gas mixture, the gas mixture should be passed through a drying tube containing anhydrous copper sulphate, followed by a wash bottle containing lime water.
(13) test acidic or alkaline gases: test hydrogen chloride gas, first distilled water to wet the blue litmus paper, and then test paper to make it turn red; test ammonia gas, first distilled water to wet the red litmus paper, and then test paper to make it turn blue.
(14) metal and salt solution replacement reaction: mixed solution and a metal replacement reaction order is "first far" "after the near"; metal mixtures and a salt solution replacement reaction order is also "first far" "then close". For example, if Al and Mg react with FeCl3 solution at the same time, Mg is far away from Fe, and Al is close to Fe (in the order of the metal activity table).
Fifteen, the reaction of some of the laws:
①Ba2 + reaction with Ba2 + white precipitate insoluble in dilute HNO3 must be SO42 -, the precipitate for BaSO4.
②Ag + reaction with Ag + reaction to produce a white precipitate insoluble in dilute HNO3 must be Cl -, the precipitate for the AgCl.
3 and hydrochloric acid reaction to produce a The reaction with hydrochloric acid to produce a gas that can make clarified limewater cloudy must be CO32- (may also be HCO3- ions, but generally disregarded) * All carbonates and acids can react to produce CO2 gas.
4 Reaction with a base to produce a gas (NH3) that turns wet red litmus paper blue must be NH4+ (i.e., an ammonium salt).
*The only gas that appears alkaline when dissolved in water is NH3 (NH3+H2O=NH3-H2O).
5SO42- and Cl- exist at the same time, if you want to test, then you must first test with Ba(NO3)2 solution and get rid of SO42-, and then use AgNO3 solution to test Cl-.
6 soluble bases can not be decomposed by heating, only insoluble bases can be decomposed by heat. cu(OH)2 △ CuO + H2O.
7 soluble carbonates can not be decomposed by heating, only insoluble carbonates can be decomposed by heat. caCO3 = CaO + CO2 ↑ (Acidic carbonates are also unstable, easy to decompose: 2NaHCO3 = Na2CO3 + H2O). Na2CO3+H2O+CO2↑).
XVI, experiments in the law:
① Where the solid heating gas are selected potassium permanganate O2 device (solid-solid heating type);
Where the solid and the liquid reaction and do not need to be heated to make gas are selected hydrogen peroxide O2 device (solid-liquid non-heating type).
② Where the test tube solid heating, should be preheated, the mouth of the test tube should be slightly downward sloping.
③Where the gas produced is insoluble in water (does not react with water), it can be collected by the drainage method.
Where the gas is denser than air, can be collected by upward air displacement method.
Any gas that is less dense than air can be collected by the downward air displacement method.
④ Whenever a gas is made, the gas tightness of the device should be checked first, the conduit should be exposed to the rubber stopper for 1-2 ml, and the iron clamp should be clamped 1/3 of the way from the mouth of the tube.
⑤ Whenever a long-necked funnel is used for gas production experiments, the end of the long-necked funnel should be inserted under the liquid surface.
6 Whenever a flammable gas is ignited, its purity must first be tested.
⑦Whenever using toxic gases in experiments, always dispose of the exhaust gas at the end.
8 Where the use of reducing gases to reduce metal oxides, it must be "one pass, two points, three extinguished, four stop".
XVII, the basic operation of the experiment in the data:
1, to add alcohol to the alcohol lamp to use the funnel, but the amount of alcohol shall not exceed the volume of the body of the lamp with a test tube to the liquid heated, not less than .
2. When oscillating a liquid in a test tube, the volume of the liquid should not exceed the volume of the test tube by more than .
3, with a test tube to heat the liquid, should also pay attention to the liquid volume should not exceed the volume of the test tube . When heating the test tube should be tilted at an angle of about 45 degrees to the surface of the table.
4, when heating a solid in a test tube, the clamp should be placed at a distance from the mouth of the tube.
4, the tray balance can only be used for rough weighing, can weigh to 0.1 grams.
5, if the acid solution accidentally stained skin or clothing, immediately rinse with more water (if concentrated sulfuric acid, must be quickly wiped with a rag, and then rinsed with water), and then with the solute mass fraction of 3 ∽ 5% of sodium bicarbonate solution to rinse.
6, in the experiment to take drugs, if there is no indication of dosage, generally should be taken according to the smallest amount: 1 ∽ 2 ml of liquid, solid only need to cover the bottom of the test tube.
7, the use of test tube clamps, should be from the bottom of the test tube up sets, fixed in the mouth of the test tube from the place.
Straight to the exam - Chemistry Summary IV
First of all, please read and memorize the following diagram, which is a summary of all the basic concepts and principles of junior high school chemistry.
Following this diagram, let's summarize them one by one
The difference between chemical and physical changes.
Changes in matter are categorized as chemical and physical changes, on a macro level: the essential difference between the two is the presence or absence of other substances. There are other substances generated, the chemical change, and vice versa for the physical change. From the microscopic point of view: the essential difference between the two is whether the particles that constitute the original substance change. If the composition of the original material particles itself changed into other substances particles, the change is a chemical change; if the composition of the original material particles only because of the distance between the particles and other factors such as change, while the particles themselves did not change, the change is a physical change. It should be noted that these are in the case of no change in the internal structure of the nucleus; if the internal structure of the nucleus is changed, the change is physical. So the statement that a change in which a new substance is produced is a chemical change is incorrect.
For example: , there is a new substance produced, but this is a physical reaction.