Basic Concepts:
1. Chemical Change: a change that produces other substances
2. Physical Change: a change that does not produce other substances
3. Physical Properties: properties that are manifested without the need for a chemical change
(e.g.: color, state, density, odor, melting point, boiling point, Hardness, water solubility, etc.)
4, chemical properties: substances in the chemical changes in the properties
(such as: flammability, flammability, oxidation, reduction, acidity and alkalinity, stability, etc.)
5, pure: composed of a substance
6, mixture: composed of two or more pure substances, the substances are to maintain their original nature
7, element: with the same nuclear charge (ie, the number of protons) of a class of atoms of the general term
8, atoms: the smallest particles in the chemical changes in the chemical changes can not be subdivided
9, molecules: the smallest particles of the substance to maintain the chemical nature of the chemical changes can be subdivided
10, monomers: composed of the same elements of the purity of the material
11, compounds: composed of different elements of the pure substance
12, oxide: compounds composed of two elements, one of which is the element oxygen
13, chemical formula: with the symbols of the elements to indicate the composition of substances in the formula
14, the relative atomic mass: the mass of a carbon atom 1/12 as a standard, the other atoms compared with it from the mass of a carbon atom, the mass of a carbon atom, the mass of the other atoms, the mass of the other atoms, the mass of the other atoms with it compared with the obtained
14, relative atomic mass: a carbon atom as a standard. The mass of other atoms compared with the value obtained
An atom's relative atomic mass =
Relative atomic mass ≈ number of protons + number of neutrons (because the mass of atoms is concentrated in the nucleus)
15, the relative molecular mass: the sum of the relative atomic mass of the atoms of the chemical formula
16, ions: the atoms or clusters of atoms with an electric charge
17, ion: a group of atoms with an electric charge
18, ion: a group of atoms with a charge
19, ion: an atom with a charge
17, the structure of atoms:
Atoms, ions of the relationship:
Note: in the ions, the number of nuclear charges = the number of protons ≠ the number of electrons outside the nucleus
18, the four basic types of chemical reactions:
① Chemistry: the reaction of two or more substances to produce a substance
e.g.: A + B = AB
② decomposition reaction: from a substance to produce two or more other substances
e.g.: AB = A + B
③ replacement reaction: from a monomer and a compound to react, to produce another monomer and another compound of the reaction
e.g.: A + BC = AC + B
④ complex decomposition reaction: from the two compounds Complex decomposition reaction: a reaction in which two compounds exchange components with each other to produce two other compounds
e.g., AB + CD = AD + CB
19. Reduction reaction: a reaction in which the oxygen of an oxygen-containing compound is taken away from the compound (not one of the basic reaction types in chemistry)
Oxidation reaction: a chemical reaction in which a substance reacts with oxygen (not one of the basic reaction types in chemistry)
Slow oxidation: slow, even imperceptible oxidation reaction
Spontaneous combustion: spontaneous combustion caused by slow oxidation
20, catalysts: in the chemical change can change the rate of chemical reaction of other substances, but its own quality and chemical properties before and after the change in the chemical change are no change in the matter (Note: 2H2O2 === 2H2O + O2 ↑ this reaction)
The catalyst is a catalyst, but it is not a catalyst. MnO2 is a catalyst)
21, the law of conservation of mass: the sum of the masses of the substances participating in a chemical reaction is equal to the sum of the masses of the substances produced after the reaction.
(Before and after the reaction, the number, type, and mass of atoms remain the same; the types of elements also remain the same)
22, solution: one or more substances are dispersed into another substance to form a homogeneous, stable mixture
Components of a solution: solvent and solute. (The solute can be solid, liquid or gas; solid, gas dissolved in liquid, solid, gas is a solute, liquid is a solvent; two liquids dissolve each other, the amount of a more solvent, the amount of a less is a solute; when there is water in a solution, no matter how much water, we are accustomed to water as a solvent, the other for the solute.)
23, solid solubility: at a certain temperature, a solid substance in 100 grams of solvent to reach saturation when the mass of dissolved, it is called this substance in this solvent solubility
24, acid: ionization of all the cations generated by hydrogen ions are compounds
such as: HCl = == H + + Cl -
HNO3 == H+ + NO3-
H2SO4==2H+ + SO42-
Bases: compounds in which all the anions produced during ionization are hydroxide ions
e.g., KOH == K+ + OH -
NaOH == Na+ + OH -
Ba(OH)2 ==Ba2+ + 2OH -
Salt: compounds that produce metal ions and acid ions when ionized
such as: KNO3==K+ + NO3-
Na2SO4==2Na+ + SO42-
BaCl2==Ba2+ + 2Cl -
25, acidic oxides (belonging to the non-metallic oxides): all with the alkali reaction, the formation of salt and water oxides <
25, acid oxides (belonging to non-metallic oxides): all with alkalis, reaction. Generate salt and water oxides
Basic oxides (belonging to the metal oxides): all can react with the acid to produce salt and water oxides
26, crystalline hydrates: substances containing water of crystallization (eg: Na2CO3 .10H2O, CuSO4 . 5H2O)
27, deliquescence: a substance can absorb moisture in the air and become wet phenomenon
weathering: crystalline hydrate at room temperature in dry air,
can gradually lose the water of crystallization and the phenomenon of becoming a powder
28, combustion: combustible with oxygen occurs with a kind of luminescence and heat of the violent oxidation reaction
burning conditions: ① combustible; ② oxygen (or air); ③ combustible temperature to reach the ignition point.
Basic knowledge, theory:
1, the composition of air: nitrogen accounted for 78%, oxygen accounted for 21%, the rare gases accounted for 0.94%,
carbon dioxide accounted for 0.03%, other gases and impurities accounted for 0.03%
2, the main air pollutants: NO2, CO, SO2, H2S, NO and other substances
3, the chemistry of other common gases
3, other common gases, the chemical reaction of combustion. >3, the chemical formula of other common gases: NH3 (ammonia), CO (carbon monoxide), CO2 (carbon dioxide), CH4 (methane),
SO2 (sulfur dioxide), SO3 (sulfur trioxide), NO (nitrogen monoxide),
NO2 (nitrogen dioxide), H2S (hydrogen sulfide), HCl (hydrogen chloride)
4, common acid roots or ions: SO42-(sulfate), NO3-(nitrate), CO32-(carbonate), ClO3-(chlorate),
MnO4-(permanganate), MnO42-(manganate), PO43-(phosphate), Cl-(chloride),
HCO3-(bicarbonate), HSO4-(hydrogen sulfate) (hydrogen phosphate), HPO42-(hydrogen phosphate),
H2PO4-(dihydrogen phosphate), OH-(hydroxide), HS-(hydrogen sulfate), S2-(sulfur ion),
NH4+(ammonium root or ammonium ion), K+(potassium ion), Ca2+(calcium ion), Na+(sodium ion),
Mg2+(magnesium ion), Al3+ (aluminum ions), Zn2+ (zinc ions), Fe2+ (ferrous ions),
Fe3+ (ferrous ions), Cu2+ (copper ions), Ag+ (silver ions), Ba2+ (barium ions)
The valence of each element or group of atoms corresponds to the charge of the above ions: text P80
Monovalent potassium-sodium-hydrogen and silver, divalent calcium-magnesium-barium and zinc ;
One or two copper and mercury and two or three iron, and trivalent aluminum comes to tetravalent silicon. (Oxygen -2, chlorine in chloride is -1, fluorine -1, bromine is -1)
(In monomers, the element's valence is 0; in compounds, the algebraic sum of the valences of the elements is 0)
5, chemical formula and valence:
(1) the significance of the chemical formula: ① macroscopical significance: a. to indicate a substance;
b. to indicate the substance's elemental composition;
② micro meaning: a. represents a molecule of the substance;
b. represents the molecular composition of the substance;
3 quantitative significance: a. represents the ratio of the number of atoms in a molecule of a substance;
b. represents the ratio of mass of the elements that make up the substance.
(2) the reading and writing of the chemical formula of the monomers
① directly with the symbols of the elements: a. metal monomers. Such as: potassium K copper Cu silver Ag, etc.;
b. Solid non-metals. Such as: carbon C sulfur S phosphorus P, etc.
c. Rare gases. Such as: helium (gas) He neon (gas) Ne argon (gas) Ar, etc.
② multi-atomic molecules of monomers: its molecules are composed of several atoms of the same kind on the lower right corner of the symbol of the element to write a few.
such as: each oxygen molecule is composed of 2 oxygen atoms, the chemical formula for oxygen O2
diatomic molecules monomers chemical formula: O2 (oxygen), N2 (nitrogen), H2 (hydrogen)
F2 (fluorine), Cl2 (chlorine), Br2 (liquid bromine)
multi-atomic molecules monomers chemical formula: O3 ozone, etc.
(3) compounds chemical formula reading and writing: first read after writing, after writing first read
① compounds composed of two elements: read "a chemical a", such as: MgO (magnesium oxide), NaCl (sodium chloride)
② compounds composed of acids and metal elements: read "a certain acid a", such as: KMnO4 (potassium permanganate), K2MnO4 (potassium manganate)
MgSO4 (magnesium sulfate), CaCO3 (calcium carbonate)
(4) according to the chemical formula to determine the chemical valence of the elements, based on the elemental valence of the compounds written out in the chemical formula:
(1) Determination of elemental valence is based on the fact that the algebraic sum of positive and negative valence in a compound is zero.
② Steps to write chemical formulas based on elemental valence:
a. Write the element symbols and label the valence according to the elemental valence of positive left and negative right;
b. See if the elemental valence has an approximate number and approximate to the most simplified ratio;
c. Cross-correlation of the valence that has been approximated to the most simplified ratio is written in the lower right-hand corner of the symbol of the element.
6. Textbook P73. to memorize the 27 elements and their symbols and names.
Electron arrangement outside the nucleus: 1-20 elements (to memorize the name of the element and the atomic structure diagram)
arrangement law: ① each layer of up to 2n2 electrons (n indicates the number of layers)
② the outermost layer of electrons not more than 8 (the outermost layer is the first layer of not more than 2)
③ first full of the inner layer and then row the outer layer
Note: The chemical properties of an element depend on the number of electrons in the outermost layer
Metallic elements Atoms have an outermost number of electrons < 4, are prone to lose electrons and are chemically active.
Nonmetallic elements Atoms with an outermost number of electrons ≥ 4, easy to gain electrons, chemically active.
Rare gas elements Atoms have 8 electrons in the outermost layer (He has 2), stable structure, stable properties.
7, the principle of writing chemical equations: ① based on objective facts; ② follow the law of conservation of mass
Steps in writing chemical equations: "write", "with", "note " "etc.".
8, the expression of acidity and alkalinity - PH value
Instructions: (1) PH = 7, the solution is neutral; PH value & lt; 7, the solution is acidic; PH value & gt; 7, the solution is alkaline.
(2) The closer the PH value is to 0, the more acidic it is; the closer the PH value is to 14, the more alkaline it is; the closer the PH value is to 7, the weaker the acidity and alkalinity of the solution, the closer it is to neutrality.
9, the order of metal activity table:
(potassium, calcium, sodium, magnesium, aluminum, zinc, iron, tin, lead, hydrogen, copper, mercury, silver, platinum, gold)
Instructions: (1) the more the left of the metal activity will be the stronger, the metal on the left side of the metal can be displaced from the right side of the metal in the salt solution of the metal out of the metal
(2) ranked in the left side of the hydrogen of the metal, the metal can be from the acid hydrogen; those to the right of hydrogen cannot.
(3) potassium, calcium, sodium three metals are more active, they react directly with the water in the solution to replace hydrogen
10, the structure of substances:
11, the meaning of chemical symbols and writing:
(1) the meaning of the chemical symbols: a. Elemental symbols: ① indicates an element; ② indicates that the element of an atom.
b. Chemical formula: point 5, sub-point (1) of this knowledge
c. Ionic symbols: indicate ions and the number of charges they carry.
d. Symbol of valency: indicates the valency of the element or group of atoms.
When the symbol is preceded by a number (the valence symbol has no number), the meaning of the constituent symbols at this point indicates only the number of particles of that kind.
(2) the writing of chemical symbols: a. Atomic representation: expressed in terms of elemental symbols
b. molecular representation: expressed in terms of chemical formulas
c. ionic representation: expressed in terms of ionic symbols
d. valence representation: expressed in terms of the valence symbols
Note: the three kinds of particles: atoms, molecules and ions are not only "1". When the number is more than "1", it can only be added in front of the symbol, not elsewhere.
12, atoms, molecules, ions, elements and substances (pure substances and mixtures):
13,
14, the production of gases commonly used generator and collection device:
Generator
collection device
[solid (+solid)]
[solid + liquid]
Simple device [solid + liquid] Drainage method upwards
Exhaustion of air method downwards
Exhaustion of air method
15. Laboratory methods of production of three gases and their differences:
Gases Oxygen (O2) Hydrogen (H2) Carbon dioxide (CO2)
Pharmaceuticals Potassium permanganate (KMnO4) or hydrogen peroxide (H2O2) and Manganese dioxide (MnO2)
[solid (+solid)] or [solid + liquid] Zinc grains (Zn) and hydrochloric acid (HCl) or dilute sulfuric acid (H2SO4)
[solid + liquid] Limestone (marble) (CaCO3) and dilute hydrochloric acid (HCl)
[solid + liquid]
Reaction principle 2KMnO4 == K2MnO4+ MnO2
+O2↑
or 2H2O2 ==== 2H2O+O2↑ Zn+H2SO4=ZnSO4+H2↑
Zn+2HCl=ZnCl2+H2↑
CaCO3+2HCl=CaCl2+H2O+CO2↑
Instrumental Setup P36 Figure 2. -17 (e.g., A of 14)
or P111. Fig. 6-10 (B or C of 14) P111. Fig. 6-10
(e.g., B or C of 14) P111. Fig. 6-10
(e.g., B or C of 14)
Test Use a wooden strip with a spark on it and stick it into the gas cylinder, if the strip rekindles it's oxygen; otherwise, it's not oxygen Ignite the Strip of wood, into the bottle, the flame on the strip of wood extinguished, the mouth of the bottle flame light blue, the gas is hydrogen Passed into the clarified lime water to see if it becomes cloudy, if cloudy is CO2.
Collection Methods ① drainage method (not easily dissolved in water) ② bottle top upward air exhaust method (density than air) ① drainage method (difficult to dissolve in water) ② bottle top downward air exhaust method (density than air) ① bottle top upward air exhaust method (less dense than air) air method
(density is greater than air)
(can not be collected by drainage method)
Check full
(test of purity) with sparks of wood, placed flat on the mouth of the cylinder, if the wooden bar rekindled, the oxygen has been full, otherwise it is not full <1> with the thumb to plug the mouth of the test tube full of hydrogen; <2> close to the flame, remove the thumb to light the fire <
If there is a "poof" sound, the hydrogen is pure; if there is a sharp popping sound, the hydrogen is impure Use a burning stick of wood and place it flatly on the mouth of the cylinder; if the flame goes out, the cylinder is full; otherwise, it is not full
Positioned Positively placed Inverted Positively placed
Precautions ①Check that the device is tight
(When the first drug is produced by the following means, it is not necessary to check that it is tight). (When the first drug is used, the following should be paid attention to)
②The mouth of the test tube should be slightly tilted downward (to prevent the small droplets of water condensed at the mouth of the test tube from flowing back into the bottom of the test tube and rupturing the test tube)
③When heating the test tube, the test tube should be heated evenly first, and then focus on the drug part of the heating.
④ after the drainage method of collecting oxygen, first withdraw the catheter and then withdraw the alcohol lamp (to prevent the backflow of water in the sink, so that the test tube rupture) ① check the gas tightness of the device
② long-necked funnel mouth to be inserted under the liquid surface;
③ before ignition of hydrogen, be sure to test the purity of the hydrogen (air, the volume of hydrogen to reach the total volume of 4%-74.2% ignition will explode). 74.2% ignition will explode.) ① check the tightness of the device
② long-necked funnel with the mouth of the tube to be inserted under the liquid surface;
③ can not be collected by draining
16, the properties of some important common gases (physical and chemical properties)
Substances Physical Properties
(usual conditions) Chemical Properties Purpose
Oxygen
( O2) colorless and odorless gas, not easily soluble in water, slightly denser than air
①C + O2 == CO2 (emits white light, emits heat)
1, for breathing
2, steelmaking
3, gas welding
(Note: O2 has a fluxing property, but does not have the flammability, can not be burned.)
② S + O2 == SO2 (in air - light blue flame
flame; in oxygen - violet blue flame)
③ 4P + 5O2 == 2P2O5 (produces white smoke, generating a white solid P2O5)
④ 3Fe + 2O2 == Fe3O4 ( (burning violently, sparks, emit a lot of heat, produce a black solid)
⑤ candle burning in oxygen, emitting white light, heat
Hydrogen
(H2) colorless and odorless gas, insoluble in water, density is smaller than the air, it is the lightest gas. ① Flammability:
2H2 + O2 ==== 2H2O
H2 + Cl2 ==== 2HCl 1, filler gas, flying ships (less dense than air)
2, synthesize ammonia, hydrochloric acid
3, gas welding, gas cutting (flammable) 4, refinement of metals (reductive)
② Reduction:
H2 + CuO === Cu + H2O
3H2 + WO3 === W + 3H2O
3H2 + Fe2O3 == 2Fe + 3H2O
Carbon dioxide (CO2) colorless and odorless gas, denser than air, soluble in water, solid CO2 called "dry ice". Solid CO2 is called "dry ice". CO2 + H2O == H2CO3 (acidic)
(H2CO3 === H2O + CO2↑) (unstable)
1, used to extinguish fires (applying its non-combustible and non-supportive of combustion properties)
2, making beverages, fertilizers, and soda ash
CO2 + Ca(OH)2 ==CaCO3↓ + H2O ( Identify CO2)
CO2 + 2NaOH == Na2CO3 + H2O
Oxidizing: CO2 + C == 2CO
CaCO3 == CaO + CO2↑ (industrial CO2)
Carbon monoxide (CO) colorless and odorless gas, slightly less dense than air, insoluble in water, poisonous gas ① flammable: 2CO + O2 == 2CO2
(the flame is blue, gives off a lot of heat, can be used as a gas fuel) 1, as a fuel
2, smelting metals
② reductive:
CO + CuO === Cu + CO2
3CO + WO3 === W + 3CO2
3CO + Fe2O3 == 2Fe Fe2O3 == 2Fe + 3CO2
(Combine with hemoglobin in the blood to destroy the blood's ability to deliver oxygen)
Solving techniques and instructions:
I. Inferring the problem solving techniques: look at the color, observe the state, detect the change, the first generation of the test, the test and get it.
1, the color of common substances: most gases are colorless, most solid compounds are white, most solutions are colorless.
2, the color of some special substances:
Black: MnO2, CuO, Fe3O4, C, FeS (ferrous sulfide)
Blue: CuSO4?5H2O, Cu (OH) 2, CuCO3, Cu2+ solution,
liquid solid O2 (light blue)
Red: Cu (bright red), Fe2O3 (bright). red), Fe2O3 (reddish brown), red phosphorus (dark red)
Yellow: sulfur (mono S), solution containing Fe3+ (brownish yellow)
Green: FeSO4?7H2O, solution containing Fe2+ (light green), basic copper carbonate [Cu2(OH)2CO3]
Colorless gases: N2, CO2, CO, O2 H2, CH4
Colored gases: Cl2 (yellow-green), NO2 (reddish-brown)
Gases with a pungent odor: NH3 (this gas can make the wet pH paper blue), SO2
Rotten egg odor: H2S
3, some common changes in the judgement:
① white precipitate and insoluble in dilute nitric acid or acid. Nitric acid or acid substances: BaSO4, AgCl (on these two substances)
② blue precipitate: Cu (OH) 2, CuCO3
3 red-brown precipitate: Fe (OH) 3
Fe (OH) 2 is a white flocculent precipitate, but in the air quickly turned into a gray-green precipitate, and then turned into a reddish-brown precipitate Fe (OH) 3
4 Precipitation can be used to determine the amount of nitric acid and not dissolved in dilute nitric acid, or acid.
④ precipitate soluble in acid and gas (CO2) released: insoluble carbonate
⑤ precipitate soluble in acid but no gas released: insoluble alkali
4, acid and the corresponding acidic oxides of the link:
① acidic oxides and acids can be reacted with bases to form salt and water:
CO2 + 2NaOH == Na2CO3 + H2O (H2CO3 + 2NaOH == Na2CO3 + 2H2O)
SO2 + 2KOH == K2SO3 + H2O
H2SO3 + 2KOH == K2SO3 + 2H2O
SO3 + 2NaOH == Na2SO4 + H2O
H2SO4 + 2NaOH == Na2SO4 + H2O
Acid oxides and acids react with bases to form salts and water. 2NaOH == Na2SO4 + 2H2O
② acidic oxides react with water to form the corresponding acid: (the valence of each element remains unchanged)
CO2 + H20 == H2CO3 SO2 + H2O == H2SO3
SO3 + H2O == H2SO4 N205 + H2O == 2HNO3
5. Connection between alkali and corresponding alkaline oxides:
① Both alkaline oxides and alkalis can react with acids to form salt and water:
CuO + 2HCl == CuCl2 + H2O
Cu(OH)2 + 2HCl == CuCl2 + 2H2O
Cu(OH)2 + 2HCl == CuCl2 + 2H2O
Cu(OH)2 + 2HCl == CuCl2 + 2H2O
CaO + 2HCl == CaCl2 + H2O
Ca(OH)2 + 2HCl == CaCl2 + 2H2O
②Basic oxides react with water to form their corresponding bases: (the resulting base must be soluble in water, otherwise the reaction can not occur)
K2O + H2O == 2KOH Na2O + H2O == 2NaOH
BaO + H2O == Ba(OH)2 CaO + H2O == Ca(OH)2
3) Insoluble bases decompose into their corresponding oxides and water when heated:
Mg(OH)2 == MgO + H2O Cu(OH)2 == CuO + H2O
2Fe (OH)3 == Fe2O3 + 3H2O 2Al(OH)3 == Al2O3 + 3H2O
II. Solving experimental questions: see what the question is asking for, what is to be done, and what is the purpose of doing so.
(a), the gas used in the experiment is required to be relatively pure, remove common impurities specific methods:
① water vapor available: concentrated flow acid, CaCl2 solid, soda lime, anhydrous CuSO4 (and can test the impurities
quality with or without water vapor, there is a color of the white → blue), quicklime, etc.
② available in addition to CO2: Clarified lime water (can test the impurities in the presence of CO2), NaOH solution,
KOH solution, soda lime, etc.
③ in addition to HCl gas can be used: AgNO3 solution (can test the impurities in the presence of HCl), lime water,
NaOH solution, KOH solution
In addition to the principle of gaseous impurities: a substance to absorb the impurities or react with the impurities, but not the impurities. or react with the impurity, but not absorb or react with the active ingredient, or generate new impurities.
(ii), the experiments note:
① anti-explosion: ignition of flammable gases (such as H2, CO, CH4) or CO, H2 reduction of CuO, Fe2O3, before the purity of the gas should be tested.
② anti-boiling: when diluting concentrated sulfuric acid, pour concentrated sulfuric acid into water, not water into concentrated sulfuric acid.
③ anti-poisoning: when conducting experiments on the properties of toxic gases (eg: CO, SO2, NO2), in
ventilated kitchens; and pay attention to the treatment of the exhaust gas: CO ignited and burned;
SO2, NO2 absorbed with lye.
④Anti-backsiphonage: heat to produce and collect the gas by draining, pay attention to the order of lights out.
(c), common accidents:
① acid flow to the table, rinse with NaHCO3; alkali flow to the table, rinse with dilute acetic acid.
② Stained skin or clothing:
Ⅰ, acid first rinse with water, and then rinse with 3 - 5% NaHCO3;
Ⅱ, alkali rinse with water, and then coated with boric acid;
Ⅲ, concentrated sulfuric acid should be wiped with a rag, and then do the first step.
(D), laboratory production of the three gases in the common impurities to be removed:
1, the system of O2 impurities to be removed: water vapor (H2O)
2, hydrochloric acid and zinc grains H2 system to be removed impurities: water vapor (H2O), hydrogen chloride gas (HCl, hydrochloric acid mist) (with dilute sulfuric acid did not have this impurity)
3, the production of CO2 impurities to be removed impurities: water vapor (H2O), hydrogen chloride gas (HCl)
Reagents in addition to water vapor: concentrated stream of acid, CaCl2 solid, soda lime (the main components are NaOH and CaO), quicklime, anhydrous CuSO4 (and can be tested for impurities in the presence or absence of water vapor, there is a color of the color by the white ?ú blue) and so on
In addition to the reagents of HCl gas: AgNO3 solution (and can test the impurities in the presence or absence of HCl), clarified lime water, NaOH solution (or solid), KOH solution (or solid)
[quicklime, soda lime can also react with HCl gas]
(E), commonly used experimental methods to verify that the mixture of gases contains a gas
1, the verification of CO: (first verify that the gas mixture) There is CO2 in the gas mixture, if there is, then get rid of it first)
The gas mixture is passed into the cauterized CuO, and then the gas mixture after the cauterized CuO is passed into the clarified lime water. Phenomenon: black CuO turns red, and the clarified lime water to become turbid.
2, the verification of H2: (first verify whether the gas mixture of water, there are first removed)
The mixture of gases into the cauterized CuO, and then the mixture of gases through the cauterized CuO into the anhydrous CuSO4. The black CuO turns red and the anhydrous CuSO4 turns blue.
3, CO2 verification method: the gas mixture into the clarified lime water. Phenomenon: clarified lime water becomes turbid.
(F), self-designed experiments
1, try to design an experiment to prove that the candle contains two elements of carbon and hydrogen.
Steps of the experiment Experimental phenomenon Conclusion
1) the candle will be lit, above the flame covered with a dry clean beaker beaker wall with small droplets of water to prove that the candle has hydrogen
2) in the candle flame covered with a beaker dipped in clarified lime water Clarified lime water becomes cloudy to prove that the candle has carbon
2, try to design an experiment to prove that the CO2 does not support combustion and is denser than air.
Experiment Steps Experimental Phenomenon Conclusion Diagram
Put two candles on a rack with a step, put this rack in a beaker (as shown), light the candles, and then pour CO2 along the wall of the beaker The candles on the lower part of the step go out first, and the ones on the upper part go out later. Proof that CO2 does not support combustion and density than the nature of air
Three, solve calculation problems:
The types of calculation problems are: ① about the mass fraction (elemental and solute) of the calculations
② calculations based on chemical equations
③ by ① and ② two types of mixing in the calculations
(a), the mass fraction of solute in solution Calculation of the mass fraction of a solute in a solution
Mass fraction of solute = ╳ 100%
(ii) Calculation of the mass fraction of an element in a compound (pure substance)
Mass fraction of an element = ╳ 100%
(iii) Calculation of the mass fraction of a compound in a mixture
Mass fraction of a compound = ╳ 100%
(iv) Calculation of the mass fraction of an element in a mixture
Mass fraction of an element = ╳ 100%
Or: Mass fraction of an element = Mass fraction of a compound ╳ Mass fraction of the element in the compound
(E), solution techniques
1, review the problem: read the requirements of the question, what is known, what is required, and if there is a chemical equation, first write the chemical Equation. Find the relevant formula to solve this problem.
2, according to the chemical equation calculation steps:
① set the unknown quantity
② write the correct chemical equation
3 write the relative molecular mass of the substance, known quantity, unknown quantity
④ list the proportion formula, solve
⑤ answer.