This test is divided into two parts, with a total score of 150 points and an examination time of 120 minutes.
Relative atomic mass: H:1 C:12 O:16 Na:23 Mg:24 S :32 Ca:40
School ; class ; name ; school number ; grade
Part I (***100 points)
One, multiple-choice questions (***counts for 14 questions, each question is worth 2 points, ***28 points, each question has only one option We often see the following phenomena, in which chemical changes take place ( )
A. damp clothes become dry by sunlight B. porcelain bowls break C. food becomes rancid D. paraffin wax melts
2. the human environment can cause harm ( )
A. sewage is discharged after treatment to meet the standards B. fertilizers and pesticides are used indiscriminately and abused
2. the human environment can cause harm ( )
A. sewage is discharged after treatment to meet the standards B. fertilizer and pesticides are used indiscriminately and abused
2. the human environment can cause harm ( )
3. B. the indiscriminate use of fertilizers and pesticides
C. the recycling of used batteries D. the use of solar water heaters
3. The scientist who invented the combined alkali production method and is known as the "pioneer of the alkali industry" in China is ( )
A. Hou Debang B. Zhang Qinglian C. Lavoisier D. Mendeleev
4. titanium are important metals in life and production, the following statements are not correct ( )
A. Titanium alloys can be used to make ships
B. Iron is not easy to rust in moist air because it can form a dense protective film of oxides
C. Iron in the human body is mainly found in the blood
D. Iron wire can be burned in oxygen
5. The following experimental operations are correct ( )
A B C D
6. The following statements are correct ( )
A. Alloys, synthetic fibers and synthetic rubber are important organic synthetic materials
B. Throwing away non-biodegradable waste plastics can cause "white pollution". "
c. Vitamins in the human body needs a small amount, it does not belong to the human body nutrients
D. For the human body's essential elements, the more the intake of the more conducive to human health
7. The following are common substances, by the classification of substances knowledge can be known, belong to the same - class of substances A group is ( )
A. red phosphorus, medical alcohol, methane B. iodized salt, soda ash, lime water
c. vinegar, oxygen, soy sauce D. seawater, sugar water, rainwater
8. chemical experiments, in case of accidents, should be dealt with calmly, the following practice is not correct ( )
A. accidentally spilled white phosphorus on the desktop, immediately swept into the
B. accidentally sulfuric acid on the skin, immediately rinse with plenty of water, and then coated with 3%-5% sodium bicarbonate solution
C. accidentally knocked over the alcohol lamp, spilled alcohol on the table burned, immediately put out with a wet cloth
D. accidentally sodium hydroxide solution on the skin, immediately rinse with plenty of water, and then coated with boric acid solution
9. The following chemical equations are correctly written ( )A. Mercury oxide decomposes by heating: HgO Hg+O2↑
B. Iron filings dissolve in dilute sulfuric acid: 2Fe+3H2SO4=== Fe2(SO4)3+3H2↑
C. Iron wire burns in oxygen: 3Fe+2O2 Fe3O4
D. Table salt dissolves in potassium nitrate. Table salt dissolved in potassium nitrate solution: NaCl + KNO3 NaNO3 + KCl
10. As shown in the figure, desalination of seawater can be used to pressurize the desalination membrane on the right side of the seawater, water molecules can be desalinated through the membrane to enter the left side of the pool of freshwater, and seawater ions can not be desalinated through the membrane, thus obtaining fresh water. After the pressurization of seawater on the right side of the composition of the change in the analysis, the correct ( )
A. solute mass increased B. solvent mass decreased
C. solution mass is unchanged D. solute mass fraction decreased
11. As shown in the figure, the two molecules of the A molecule reaction to generate three molecules of the B molecule and a molecule of the C molecule, then from the information obtained from the diagram, is incorrect
A. the type of molecules in the chemical reaction has changed B. the reaction type of the reaction is decomposition reaction
C. the reaction of the C substance belongs to the monomers D. the B molecule contains an A atom, a B atom
12. there are a variety of ways of thinking in chemistry, which is commonly used in reasoning thinking method. The following reasoning is correct ( )
A．Organic substances produce carbon dioxide when they are completely burned, so organic substances must contain carbon element
B．Neutralization reaction produces salt and water, so the reaction that produces salt and water must be a neutralization reaction
C．Burning is generally accompanied by a luminous, feverish phenomenon, so there are luminous, feverish phenomenon is burning
D． D. oxides contain oxygen, so compounds containing oxygen must be oxides
13. remove impurities in the following substances (impurities in parentheses), the choice of reagents and the correct method of operation of a group ( )
Option substance to be purified Selected reagent method of operation
A CaO (CaCO3) water Dissolve, filtering, crystallization
B CuSO4(H2SO4) Sodium hydroxide solution Filtration
C Cu(CuO) Dilute hydrochloric acid Dissolving, filtering, washing, drying
D CO2(CO) Oxygen Ignition
14. The following images can correctly reflect the corresponding narrative relationship is ( )
Figure A represents a certain amount of charcoal reduction of copper oxide, the relationship between the mass of the remaining solid and the reaction time
Figure B represents the addition of potassium nitrate crystals to the saturated potassium nitrate solution at t ℃, the relationship between the mass fraction of the solute and the amount of the addition
Figure C represents a certain amount of dilute sulfuric acid and zinc grains, the relationship between the mass of solution and reaction time
Figure C represents a certain amount of dilute sulfuric acid and zinc grains, the relationship between the solution The mass of the solution is related to the reaction time
Figure D shows that sodium hydroxide is added to a mixed solution of sulfuric acid and copper sulfate, and the relationship between the mass of the precipitate and the amount of the added solution
A B C D
II. Fill-in-the-blanks questions (This question has 5 sub-questions, ****20 points)
15. (2 points) The structure of the atom of a certain element is shown in the diagram:
The value of X is , according to the atomic structure schematic diagram of the element, the information that cannot be obtained directly
is ________ (fill in the number).
① nuclear charge ② relative atomic mass ③ number of electron layers ④ number of outermost electrons
16. (4 points) Soft water, hard water, white vinegar and alcohol are common colorless liquids that are very similar in appearance, of which:
(1) the one whose pH is less than 7 is _________________; (2) the one that has a special odor is _______________ ;
(3) The reagent that can be added to distinguish hard water from soft water is ______________ ;
(4) The most common method used in life to convert hard water into soft water is _________________ .
17. (5 points) People's daily life can not be separated from the metal, the development and application of new high-tech materials also need metal.
(1) According to the following figure of the metal application examples inferred that the metal has the physical properties of ,
, .
Electrical wires Metal wires Cookware
(2) Most of the metals used in everyday life are alloys. The table below lists the main components and properties of some common alloys.
Alloys Main Properties of Alloys Main Components and Properties of Pure Metals
Soldering Tin Melting Point 183°C Tin: Melting Point 232°C; Lead: Melting Point 327°C.
Duraluminum Good strength and hardness Aluminum, copper and magnesium. Hardness is small, soft.
Stainless steel Good corrosion resistance Iron, chromium, nickel, etc.. Pure iron does not resist corrosion as well as stainless steel.
From the above table, it can be inferred that the advantages of alloys are generally (fill in the ordinal number) compared to the pure metals that make up the alloy .
① lower strength ② higher hardness ③ higher melting point ④ better resistance to corrosion
18. (4 points) in order to explore some of the properties of ammonia (NH3), a student did the following experiments:
The following chart from left to right is the experiments he did and the corresponding phenomena.
A B C D
(1) Through the experiment, Mr. Ming can conclude that the three properties of ammonia are: ①; ②; ③ ;
(2) In operation A, the gas guide tube should be as close as possible to the bottom of the test tube, and its purpose is .
19. (5 points) fire will bring great losses to people's lives and property, the following is a student in the event of a fire in the event of the design of the emergency program (fire extinguishing and self-help measures).
①When the fire is small, immediately use a variety of fire extinguishing equipment to extinguish the fire;
②In case of indoor fire, open the doors and windows, and try to let the smoke out of the windows and doors.
③In the process of extinguishing the fire or escape, cover your mouth and nose with a wet towel.
④When a fire is caused by a gas leak, turn off the gas first and then put out the fire.
Please answer the following questions according to the student's emergency program:
(1) In the emergency program program, there is one less indispensable measure, which is
;
(2) In the fire-fighting and self-rescue measures, there is one that is not adequate, which is (fill in the ordinal number)
Reason is;
(3) Supplement to the program: when a fire started by electrical appliances and wires short-circuiting, it should be turned off first. short-circuit triggered a fire, should first , and then extinguish the fire;
(4) in the process of extinguishing the fire or escape, use a wet towel to cover the mouth and nose, which is the reasoning is
.
Third, (this question has 2 sub-questions, ***15 points)
20. (7 points) American scientists Carl? Crist succeeded in making d get salt grain-sized nitrogen 5 (chemical formula for N5), in the experiments to produce nitrogen 5, it had exploded, destroying some of the equipment in the laboratory, so scientists believe that if the substance can be made to remain stable; it may become an ideal fuel for the rear stage of rockets and missiles. Nitrogen 5 is a combination of five nitrogen atoms arranged in a V-shape and is so chemically unstable that it needs to be kept in dry ice at -80 degrees Celsius.
(1) Compare the similarities and differences between nitrogen gas and nitrogen 5
Nitrogen gas (N2) Nitrogen 5 (N5)
Differences
Molecular Composition
Physical Properties Gases
Chemical Properties Stable
Similarities
(2) Based on the above account, what do you think are the uses of N5 in the field of applications? (Write two)
(1) ; (2) .
21. (8 points) A ~ D are common substances in junior high school chemistry, and have the transformation relationship shown in the figure (reaction conditions,
other reactants and excess products have been omitted).
Please write the chemical formulas of the following substances as required:
(1) If A is a colorless liquid at room temperature,
and D is CuO. then: A is ,
Write the chemical reaction equation: C + D → A . This reaction shows that C has the property of , the basic type of reaction;
(2) If A is a white solid insoluble in water at room temperature, and C is one of the main gases that form the greenhouse effect. Then: A , write the chemical reaction equation: B → D .
Four, (this question has 2 sub-questions, ***24 points)
22. (12 points) the following figure shows the laboratory commonly used experimental device:
(1) write the name of the instrument with the mark: ① ② ;
(2) room temperature, with zinc and dilute sulfuric acid reaction to produce hydrogen, should be used to generate the device is (fill in the serial number, the same below),
collecting device is;
3 laboratory with KMnO4 O2, can choose the device is; the reaction of the chemical equation is; with drainage method to collect O2 after the completion of the sink, if found in the water becomes red, the reason may be.
(4) F device can be used to measure the volume of CO2 gas generated, which put a layer of vegetable oil on the water surface is
, the original air above the vegetable oil on the results of the experiment (fill in "have" or "no") obvious The air above the vegetable oil had a significant (yes or no) effect on the results of the experiment.
23. (12 points) a student will be a small packet of copper powder and zinc powder mixture into a certain amount of silver nitrate solution, so that it reacts fully after filtration, to get a solid and blue filtrate, and the composition of the filtrate to explore.
(1) The chemical equation for the reaction between zinc and silver nitrate solution is .
(2) The students made a variety of conjectures about the solute contained in the filtrate, of which two conjectures may be valid, these two conjectures are:
(1) The solute is ___________ ___; (2) The solute is __________ ___.
(3) Please design two experimental schemes to test the above conjectures.
Scheme Experimental operation Experimental phenomenon Conclusion
Scheme 1
If
the conjecture is established
Scheme 2
If
the conjecture is established
V: Calculation (This question has 2 subtopics, ***13 points)
24. (6 points) The figure on the right shows part of the text on the label of a calcium supplement tablet. part of the text, please read carefully to answer the following questions:
(1) more types of vitamin D, including vitamin D2 chemical formula for C28H44O, try to calculate:
① relative molecular mass of vitamin D2
② vitamin D2 in carbon, hydrogen, oxygen, three elements in the mass ratio
(2) Calculation of calcium carbonate per gram of calcium tablets contain calcium of calcium carbonate in each gram of calcium tablets.
25.(7 points). In order to solve the problem of insufficient oxygen in the water, a yellowish solid is usually sprinkled into the fish pond, and the main component of this solid is calcium peroxide (CaO2), CaO2 and Na2O2 both belong to the peroxide, and their chemical properties are very similar. The chemical equation for the reaction between sodium peroxide and water is: 2Na2O2 + 2H2O = 4NaOH + O2↑
(1) Write the chemical equation for the reaction between CaO2 and H2O ;
(2) Now, 20g of the sample is weighed and added to a sufficient amount of water, resulting in the formation of 3.2g O2 (the other components of the sample do not react with water). Calculate the mass fraction of CaO2 in this sample.
Part II (***50 marks)
I. Multiple Choice (There are 7 sub-questions, each of which is worth 2 marks, ***14 marks, and each of which has 1 or 2 options that match the meaning of the
question. If there are two answers to choose 1 and correct 1 point, where there is an error does not score)
26. The following instruments, with dissolving solids, preparing solutions, heating a larger amount of liquid three purposes are ( )
A. test tubes B. measuring cylinders C. beakers D. flasks
27. the following experimental program, feasible ( )
A. by order of operation of dissolution, filtration, evaporation can be separated from the mixture of CaCl2, CaCO3
B.Adding barium chloride solution to a certain solution produces a white precipitate, which proves that the solution must be sulfuric acid
C.Burning with phosphorus in a closed container removes the oxygen in the air inside the closed container
D.Wetting the pH test paper and then dipping the glass rod into the test paper. White vinegar drops on the test paper, to determine its pH
28. Graphical data can provide a lot of information, the following is a student on the use of graphical data, which is incorrect ( )
A. According to the order of the activity of metals table, to determine whether the metal can be replaced with dilute sulfuric acid in the hydrogen
B. According to the density data table to determine the size of the volatility of the liquid substance
C. According to the solubility table to determine the size of the liquid substance
C. According to the solubility table, to determine the size of the liquid substance
C. C. According to the solubility graph, to determine the method of obtaining crystals from solution
D. According to the solubility table of acids, bases and salts, to determine whether certain complex decomposition reactions can be carried out
29. copper and concentrated sulfuric acid *** hot conditions can occur under the chemical reaction Cu + 2H2SO4 ＝ CuSO4 + SO2↑ + 2H2O, but in the industrial production of copper sulfate Not directly using concentrated sulfuric acid and copper reaction, but the copper chips in the air heating oxidation, and then immersed in dilute sulfuric acid reaction filtration, and repeated heating and immersed in the operation, you think the advantages of this is ( )
A. save energy B. does not produce pollution of the atmosphere of sulfur dioxide
C. Improve the utilization rate of sulfuric acid D. Increase the utilization rate of copper
30. use of chemical Experiments can identify some substances in life, the following table of substances can be identified in the group of substances to be identified to distinguish between the substances are ( )
to be identified substance identification method
A NaOH, Na2CO3, add dilute hydrochloric acid, and observe whether there are bubbles
B N2, 02, C02, air, with the test of the burning wood, and observe the wood burning Situation
C Cotton fiber, wool fiber, polyester Smell the smell produced by burning, observe the burning situation and ash
D Potassium chloride, potassium sulfate, phosphate powder Ca3(PO4)2 Look at the appearance, and then add water to observe whether it is soluble in water
31.In the 1920's, the acid-base proton theory put forward by a number of chemists argued that any molecules or ions that can emit protons (H+) are acids, and any molecules or ions that can release protons (H+) are acids. molecules or ions are acids, and any molecules or ions that bind protons are bases. According to this theory, the following substances do not belong to the base ( )
A. HNO3 B. HCO3- C. NH4+ D. SO42-
32. IO3- and I- can be reacted: IO3- + 5I- + 6H+ = 3I2 + 3H2O, according to the reaction, the available test paper and some of life's common substances experiments, to prove that the existence of salt in the IO3-, available substances: ① tap water ② blue litmus paper ③ potassium iodide starch paper ④ starch ⑤ salt ⑥ vinegar ⑦ white wine, the above experiments must use the substance ( )
A ① ③ B ③ ⑥ C ② ④ ⑥ D ① ② ④ ⑤ ⑦
Two, fill in the blanks (this question has three subtopics, ****10 points)
33. (3 points) biogas is one of the cleanest gaseous fuels that has been developed and used in rural areas today.
(1) The energy transformation that occurs during the production and application of biogas is: bioenergy → → heat or light energy;
(2) In addition to methane, biogas contains carbon dioxide and a small amount of hydrogen, nitrogen, hydrogen sulphide, carbon monoxide, water vapour, and the biogas is slightly foul smelling, and the foul smelling may come from other gases;
(3) In terms of safety considerations, biogas must be prevented from being used in the biogas. When using biogas, it is important to prevent the gas from mixing with .
34.(4 points) Iron was one of the first metals to be discovered and used.
(1) Pig iron contains about 4% carbon and steel contains less than 2% carbon. In ancient times, people in the high temperature of the red iron repeatedly hammered, and ultimately the pig iron into steel, which is also known as the origin of the "hundred refined into steel". Please write the above transformation process in the most critical step in the reaction of the chemical equation __________________________;
(2) Fe in compounds usually show +2 valence or +3 valence, Fe3O4 can be written in the form of oxides FeO?Fe2O3, or salt in the form of Fe(FeO2)2; Pb in compounds show +2 valence or +4 valence, then Pb3O4 can be written as the form of oxides FeO?Fe2O3, or the form of salts Fe(FeO2)2; Pb in compounds show +2 valence or +4 valence, then Pb3O4 is a compound of iron. 4 price, then Pb3O4 can also be written as or .
35. (3 points) at room temperature, the volume of roughly equal water and alcohol
(alcohol density: O.789 g / cm3) slowly injected in turn into the right figure, "thin-necked" containers (volumetric flasks), filled immediately after the plug tightly corked vibration, let it stand for a few moments, volumetric flasks have a hollow column on the upper part of the thin neck formation.
The experiment found that if the water and alcohol injection sequence is different (other conditions are the same), the formation of the length of the empty column is also different, in order to make the formation of the empty column is long, the order of the added solution is ,
Because .
Three, experimental questions (26 points)
36. Please participate in the process of a study group to carry out research and study, and assist in completing the relevant tasks:
Research topic: investigate the main components of the scale at the bottom of the kettle
References: the students of the group through the reference to the information that the natural water generally contains Ca2 +, Mg2 +, HCO3- and other ions, when heated, these ions tend to produce less soluble substances - scale (the main component is a mixture of carbonates, alkalis, etc.). At the same time, they also checked the solubility of the following substances:
Substance Ca(HCO3)2 Mg(HCO3)2 Ca(OH)2 Mg(OH)2 CaCO3 MgCO3
Solubility Soluble Soluble Slightly Soluble Insoluble Insoluble Insoluble Slightly Soluble
Proposed a conjecture: the main component of the limescale must contain Mg(OH)2 and , and may contain Ca(OH)2 and .
Design:
(1) A students in the beaker into a small amount of crushed limescale, add the appropriate amount of distilled water and stir thoroughly, take the upper layer of clear liquid and add , and there is no white precipitate, indicating that there is no Ca (OH) 2 in the limescale;
(2) B students designed the following experimental setup, to further determine the composition of the carbonate contained in the limescale, the steps are as follows:
①Assemble the apparatus according to the figure. Assemble the apparatus, 50g of scale sample into a conical flask, add a sufficient amount of an acid solution;
② Measure the increase in the mass of the substance in the drying tube for a certain period of time (see the following curve);
③ to be no longer produced in the conical flask bubbles, open the piston B, from the conduit A slowly drummed into a certain amount of air;
④ again weighed the increase in the mass of the substance in the drying tube;
⑤ Repeat the operations ③ and ④ until the mass of the substance in the drying tube remains unchanged.
a. The acid solution added in step ① is .
b. The function of device Ⅱ is ;
When a certain amount of air is slowly drummed from conduit A, the function of device Ⅰ is ____________________.
c. The students in the research group think that the scale must contain MgCO3 by simple calculations, the reason is
.
Experimental Conclusion Through the above investigation, it is known that the main components of limescale are .
37. (6 points) is known that alum [KAl (SO4) 2?12H2O] in water can be dissociated from K +, Al3 + and SO42-, a study group to explore what kind of ions in the alum play a role in water purification, to do the following experiments, please complete the experimental report:
Experimental operations, experimental phenomena, conclusions
In a cup of cloudy water with a small amount of Aluminum, the water must contain MgCO3. Add a small amount of Al2(SO4)3 to a cup of turbid water, and let it stand Al2(SO4)3 plays a role in water purification
Add a small amount of KCl to a cup of turbid water, and let it stand The water in the beaker is still turbid
Some students think that the above program only proves that Al2(SO4)3 can purify water, and that K+1 has no role in water purification, but Al3+ and SO42 -can purify water, is not perfect enough. Please carefully analyze the above experimental report and fill in the table below with the reagents and purpose you used to perfect the experiment:
Reagents used Experimental purpose
③ ④
⑤ ⑥
38. (10 points) There is a baryte ore in the minerals in nature, the main ingredient of which is BaSO4, which is not soluble in any acid, alkali and water, and pure barium sulphate can be used in medical treatment etc., a student used barite and coke as raw materials to make pure barium sulfate, part of the process is as follows (set the impurities in the mineral does not react with coke, nor dissolved in water): (East China Normal University competition tutorial P231 question 15)
(1) step ①, which elements of the chemical combination of the valence of the element increases, which elements of the chemical combination of the element decreases? ____________________,
(2) The chemical formula of the solute in solution A in step ②: ____________________ ;
(3) Write the chemical equation for the production of BaSO4 using the solute in solution A as the main raw material:
__________________________________________________________.
(4) Step ② produces the toxic gas H2S, which should be improved, in order to make the experiment not produce H2S but also obtain pure BaSO4. _________________________________________ ;
The chemical equation for the reaction in question is ____________________________________________ __ .
The 17th "Tianyuan Cup" Junior High School Chemistry Competition 2007 Guangdong preliminary round (Huizhou district) test answers
Part I ((***100 points)
I. (28 points) 1.C 2.B.3. .B 11.D 12.A 13.C 14.D
Two, fill in the blanks (***20 points) 15. (1 point per blank,***2 points) 17; ②
16. (1 point per blank,***4 points) (1) white vinegar (2) alcohol (3) suds (4) boiling (or distillation)
17. (***5 points) (1) (3 points) Electrical conductivity, ductility, thermal conductivity (2) (2 points) ② ④
18. (1 point per space,***4 points) (1) ammonia (extremely) soluble in water; ammonia density is smaller than air; ammonia and water will react chemically, the reaction of the solution is alkaline (2) so that the collected gas is more pure
19. (1 point per space,***5 points) call the police 119; ② open doors and windows to cause air convection fire increased;
cut off the power supply; to prevent inhalation of smoke poisoning
Three, (this question has two sub-questions, ***15 points) 20. (***7 points) (1) (1 point per blank,***5 points)
Each N2 molecule is made up of two nitrogen atoms each N5 molecules are made up of five nitrogen atoms
Solid
Unstable, easily decomposed
All are monomers composed of the element nitrogen
(2) (2 marks) Used as fuel, explosives and so on. (Answers reasonable can be given points)
21. (8 points) (1) A: H2O (1 point); H2 + CuO △ Cu + H2O (2 points);
reducing (1 point); replacement (1 point)
(2) A: CaCO3 (1 point); CaO + H2O = Ca (OH)2 (2 points)
IV. ( This question has 2 sub-questions,***24 points)
22. (12 points) (1) (1) long-necked funnel (1 point), collecting cylinder (1 point) (2) B (1 point), C (or E or C, E) (1 point)
(3) A (1 point); 2KMnO4 heated K2MnO4 + MnO2 + O2 ↑ (2 points); the mouth of the test tube is not plugged with cotton (2 points)
(4) to prevent the CO2 dissolved in water (or prevent CO2 and water reaction, prevent CO2 and water contact) (2 points), no (1 point)
23. (12 points) (1) (2 points) Zn + 2AgNO3=== Zn (NO3)2 + 2Ag
(2) (4 points) ① zinc nitrate and copper nitrate ② zinc nitrate, copper nitrate and silver nitrate (① and ② can be inverted order)< /p>
(3) (1 point per space, ***6 points) (other reasonable answers can be given points)
Experimental operations Experimental phenomena Conclusion
Program 1: take a small amount of filtrate in a test tube, in the filtrate, insert a copper wire (or copper) If the surface of the copper wire is unchanged
Or if there is a silvery-white solid precipitation of the surface of the wire, to prove that the conjecture ① is valid
or prove that the conjecture ② is valid
Or prove that the conjecture ② is valid
Option 2: take a small amount of filtrate in a test tube, add a few drops of dilute hydrochloric acid (or other chloride solution) If the filtrate has no obvious changes
Or if there is a white precipitate produced Prove that the conjecture ① is valid
Or prove that the conjecture ② is valid
Five: Calculation (This question has 2 subtopics, ***13 points)
24. (***6 points) (1) ① Relative molecular mass of C28H44O=12×28+1×44+16=396 (1 point)
② Mass ratio of C, H and O elements in C28H44O: (12×28):(1×44): 16=84:11:4 (2 points)
(2) Solve: per gram of calcium tablets of the element calcium The mass of calcium in each gram of calcium tablets is 0.5g ÷ 2.5 = 0.2g. (1 point)
Then the mass of calcium carbonate in each gram of calcium tablets is 0.2g ÷ = 0.5g. (2 points) (Any other reasonable solution can be given points)
25. (7 points). (1) 2CaO2 + 2H2O = 2Ca(OH)2 + O2↑ ........................ ......... (2 marks)
(2) Solution: let the mass of CaO2 in 20g of sample be x
2CaO2 + 2H2O = 2Ca(OH)2 + O2↑
144 32 (2 marks)
x 3.2g
144:32 = x:3.2g (1 point) x = 14.4 (1 point)
The mass fraction of CaO2 in this sample is .................. .................. (1 point)
Answer: the mass fraction of CaO2 in this sample is 72%.
Part II (***50 points)
I. 26, C 27AC, 28B, 29BC, 30AC, 31AC, 32B
II. Fill in the blanks (10 points) 33. (1 point for each blank,***3 points) (1) Chemical energy; (2) Hydrogen sulfide; (3) Air or oxygen
34. (***4 points) (1) C + O2 ignition of CO2 (2 points)
(2) 2PbO?PbO2 ; Pb2 (PbO4) or Pb (PbO2)2 (2 points)
35. (***3 points) first alcohol and then add water to add the empty column is longer (1 points)
Because when the water to the alcohol slowly into the alcohol, due to the density of water is greater than that of the alcohol, the more quickly penetrate the alcohol molecules in the interstices, so the formation of the empty column is longer after oscillation (2 points)
Third, the experimental questions (***26 points) 36. put forward a conjecture (1 point per blank) CaCO3 (1 point) MgCO3; (1 point)
Design (1) Na2CO3 solution (1 point); (2) a. Dilute hydrochloric acid (1 point); b. Absorption of CO2 water (1 point); Remove CO2 in the air (1 point); (2) The water is absorbed into the air (1 point); (3) The water in the air (1 point); (4) The water in the air (1 point); (5) The water in the air (1 point) (1 point); Remove CO2 from the air (1 point) c. Even if 50g of scale is all CaCO3, the mass of CO2 produced should be 22g, and the experiment measured the mass of CO2 produced > 22g (2 points)
Experimental conclusions Mg(OH)2, CaCO3, MgCO3 (2 points)
37. (1 point per blank, ***6 points) The beaker of Water becomes clarified; K+ (or potassium ions) cannot act as a water purifier
AlCl3 [Al(NO3)3, etc., write the name as well] Verify the purification of Al3+ (or aluminum ions)
Na2SO4, etc., (write the name as well) Verify that there is no purification of SO42- (or sulphuric acid Guozi)
38 . (2 points per space,***10 points) (2 points) (1) C, S; (2) BaCl2;
(3) BaCl2 + Na2SO4 = BaSO4 ↓ + 2NaCl;
(4) can be added to the step ② in the Na2SO4; and then filtered, washed to obtain pure BaSO4;
BaS + Na2SO4 =BaSO4↓+Na2S