2019 Beijing Xiangyu senior high school entrance examination three mode examination paper
1. Multiple choice questions (12 questions in total, Full Score: 12 points, 1 point for each question)
1. Fanchang kiln in Wuhu City is known as the birthplace of China 's blue and white porcelain. In the manufacturing process of ceramic ware, there must be chemical changes ()
A. Mix B. forming
C. Dry D. sintering
2. The following ancient poems contain the movement of molecules
A. Gold is not afraid of fire, wine is not afraid of alley
B. The wildfire is endless, and the spring wind blows again
C. Thousands of hammers chisel out the deep mountain, and the fire burns like idleness
D. I can 't sleep in spring and hear birds everywhere
3. The following descriptions of experimental phenomena are correct ()
A. Red phosphorus can burn in oxygen, not in air
B. Light blue flame when sulfur burns in oxygen
C. Fine wire burns in oxygen, sparks fly, and iron oxide is produced
D. The burning charcoal reaches into the cylinder containing oxygen and burns violently, giving off white light
4. The following substances are oxides ()
AO3BSiO2
CCu2 (OH) 2CO3DFe (OH) 3
5. Persimmon is one of the five major fruits in China. Its nutritional value is very high and rich in sucrose, vitamin C, iodine, calcium, phosphorus, iron and zinc, among which iodine, calcium, phosphorus, iron and zinc refer to ()
A. Element B. atom C. molecule D. ion
6. The detergent containing phosphorus contains na5p3o10, which will cause water pollution if widely used. The following statement about na5p3o10 is correct ()
A. Contains 5 oxygen molecules
B. The mass ratio of sodium and oxygen is 1: 2
C. There are two kinds of metal elements
D. The valence of phosphorus is + 5
7. The following washing methods mainly utilize the chemical properties of the substance ()
A. Wash the mobile screen with anhydrous alcohol B. wash the oil stains on the clothes with gasoline
C. Wash the salt on the clothes with clear water
8. The simple and feasible method to distinguish O2, CO and CO2 is ()
A. Put gas into clarified lime water respectively
B. Test the solubility of three gases in water
C. Put the burning wood into the bottle
D. Put the gas into the purple litmus test solution
9. The unreachable purpose of the device as shown in the figure is ()
A. Remove sediment B. lighten colored water
C. Deodorize D. turn seawater into fresh water
10. What 's inappropriate about the measures or statements of combustion and fire fighting
A. Cover the oil pan when it 's on fire to keep off oxygen
B. Cover the alcohol lamp with wet cloth to reduce its ignition point
C. Forest fires cut down trees to form a separation zone
D. In case of fire in the room, close the doors and windows in time
11. There is a bottle of potassium nitrate saturated solution at t. The following statement is correct ()
A. It must be both a concentrated solution and a saturated solution
B. When the temperature increases, the mass fraction of solute decreases
C. When the temperature is reduced, crystals are precipitated, and the remaining solution is still saturated
D. At t, the mass fraction of solute increases with the addition of KNO3 solid
12. The following experiments can achieve the purpose ()
A. verify the combustion conditions of combustibles
B. measure the content of O2 in the air
C. check the existence of CO32
D. co absorption with water
2. Answer questions (10 questions in total, 33 points in total)
13. (3 points) chemistry is closely related to our production and life.
(1) Fill in the corresponding space with the letter number of the following substances:
a. Salt water B. vitamin C. liquid oxygen D. hydrated lime E. graphite
It can be used to neutralize acid soil in agriculture;
It can be used to make pencil lead;
The main nutrients in vegetables are;
What can be used as a rocket propellant is.
(2) Energy and environment are issues that we are increasingly concerned about. To protect the environment and control pollution, we need the whole society to act together.
The three major fossil fuels include coal, natural gas, and scientists have found combustible ice on the sea floor. Its main components are the same as those of natural gas and biogas, and its chemical formula is.
Coal mainly contains carbon elements. Using coal as fuel, it mainly uses the heat generated by the reaction of carbon elements and oxygen, and generates carbon oxides at the same time. When the oxygen is insufficient, it will produce a kind of air pollution gas .
In view of the increasingly serious environmental problems, the following measures are not conducive to environmental protection (fill in the letter number).
A. Develop green transportation and promote public travel B. try to use degradable plastics to reduce white pollution
C. Domestic waste is poured into river D. waste batteries are recycled to save resources and reduce environmental pollution
14. (3 points) Figure 1 is a network diagram of metal chemical properties summarized by a student. Fig. 2 and Fig. 3 are experiments on the chemical properties of metals.
(1) The substance category of X in Figure 1 belongs to.
(2) The experimental phenomenon in Figure 2 is that the iron wire burns violently and releases heat.
(3) Fig. 3 experiment: tubes and are filled with iron powder, and a certain amount of zinc chloride solution and copper chloride solution are added respectively. After full reaction, all the substances in tubes and are poured into the same beaker, and it is found that the number of red solid substances in the beaker is significantly increased. The following statement is correct.
A. Figure a tube there must be only copper in the solid after reaction
B. Figure B there must be no iron in the solid of beaker
C. Figure B the beaker liquid must contain Zn2 +, Fe2 +, Cu2 +
(4) Write the chemical equation of reducing iron oxide with carbon monoxide in the laboratory.
15. (3) with the development of economy, energy and environment have become the focus of attention
(1) Coal, natural gas and fossil fuels are used to pulverize coal into pulverized coal for power generation
(2) At present, the energy consumed by human beings mainly comes from fossil fuels. The largescale use of fossil energy will produce SO2, Co, NO2, CO2 and other gases and dust, among which the content in the atmosphere keeps rising, leading to the enhancement of greenhouse effect. What causes global warming is acid rain (only one)
(3) Hydrogen energy is a kind of new energy which is both efficient and clean. Fuel cell vehicles using hydrogen as energy are very popular
(4) Nuclear energy is also a kind of efficient energy. The development of deuterium nuclear energy is considered as one of the main ways to solve the problems of energy and environment in the future. It is known that deuterium hydrogen belongs to the same element , and the number of protons in deuterium nucleus is
(5) When a purification device is installed on the automobile exhaust pipe, the carbon monoxide and nitric oxide gas in the exhaust gas react on the catalyst surface, producing two nontoxic gases. The chemical equation of the reaction is
16. (5 points) read the following popular science essay.
Distilled wine is a kind of wine which is produced by 'fermentation and re distillation' of grain. Chinese liquor is distilled liquor with sorghum, wheat and other grains as raw materials. Spirits above 40 degrees are mostly distilled spirits. According to Li Shizhen ' s Compendium of Materia Medica, 'wine cooking is not an ancient method. It was created in Yuan Dynasty.'.
The 'degree' of Liquor refers to the volume percentage of alcohol (ethanol) in liquor at room temperature. '53 degrees' means that there are 53 ml of alcohol in 100 ml of alcohol.
Chinese people drink white wine, there is an important indicator, called 'taste mellow', generally measured by 'viscosity', the greater the viscosity, the mellower the taste. 'Viscosity' depends on the type of molecules in the liquid and the attraction between them. The viscosity of wine mainly depends on the proportion of water and alcohol molecules. The relationship between alcohol degree and alcohol viscosity shows a curve, as shown in Figure 1.
No matter what brand of wine, more than 98% of its ingredients are water and alcohol. The flavor difference of different wines comes from 2% of other ingredients, such as aldehydes, esters and aromatic. The composition proportion of the wine is shown in Figure 2.
Alcohol can be absorbed in the mouth, stomach and small intestine. After absorption, only 10% of alcohol is excreted through respiration and urination, and the remaining 90% of alcohol reaches your liver for metabolism. The liver is like a large chemical factory, which has many channels to help the transformation of alcohol.
Acetaldehyde after alcohol transformation is toxic, which can destroy the structure of some proteins in the body, and has a great impact on the liver and pancreas. Alcohol is also toxic. Its longterm effect is toxic to the brain. After entering the body, the alcohol can reach the brain in 10 minutes, and it will stay in the brain for half a month to a month.
architectural lighting companies China is a big country of drinking. The number of people who are addicted to alcohol or alcohol has reached 200 million. The rate of chronic alcoholism has been increasing year by year.
Answer the following questions:
(1) '40 degree' liquor means that 100 ml liquor contains ml alcohol.
(2) Fig. 1 is a curve of the influence of alcohol degree on the viscosity of wine. The conclusion can be drawn from the analysis of the curve.
(3) It is speculated that the elements in ethanol, acetaldehyde and acetic acid must be.
(4) The original pulp of Maotai liquor after fermentation and distillation is about 60 degrees. It needs to be aged for more than three years before it is put on the market for sale. At this time, the degree of Maotai liquor is 60 degrees (fill in 'more than' or 'less than').
(5) The following statement is correct.
A. Chemical changes must have taken place in the process of wine brewing. B. The higher the degree, the better the taste. C. The price of different brands of wine varies greatly because of the different main ingredients. D. Drink a little to make you happy. Drink too much to hurt you. Don 't drink or drive. E. Ethanol solution can be used for medical disinfection.
17. It is a complex process to turn iron from iron ore. The iron ore, coke and limestone are added into the blast furnace together. At high temperature, the iron is reduced from the iron ore by using the carbon monoxide generated by the reaction in the furnace. As shown in the figure.
(1) Main chemical reactions in blast furnace:
C + CO2 2CO
Carbon monoxide reduces iron oxide.
(2) The blast furnace gas must contain.
An interest group simulated the chemical principle of ironmaking in the laboratory, reduced iron oxide powder with carbon monoxide, and designed a and B sets of experimental devices respectively.
(3) Clarify the cause of lime water turbidity (expressed by chemical equation).
(4) From the perspective of environmental protection and energy conservation, you think the device (serial number) is more reasonable.
18. (4 points) for the following four sets of common experimental devices, please fill in the following relevant blanks as required:
(1) Fig. 1 experiment is to use combustibles to consume oxygen in the cylinder, so that the oxygen content in the air can be inferred in the cylinder.
(2) In Figure 2, the function of water is.
(3) Fig. 3 the phenomenon that can be seen in the experiment is.
(4) Fig. 4 during the experiment, the gas produced in tube 1 is (fill in the name).
(5) Among the four experiments mentioned above, the experiment to study the composition of substances is.
19. (4 points) as shown in the figure, it is a common device for gas production in the laboratory.
(1) Write the chemical equation of oxygen production by a device.
(2) When heating solid ammonium bicarbonate, the following reaction will take place: nh4hco3nh3 + H2O + CO2. If the reaction is to be used to generate carbon dioxide and a bottle of pure carbon dioxide is collected by e device, the order of the selected device conduit connection from left to right is: a F. meanwhile, please complete the conduit in E device.
20. (2 points) the following experiments explore the factors affecting the solubility of substances. Experimental phenomena:
Almost insoluble in a
Solid soluble in B
The solid in C is soluble.
Phenomenon (fill in the serial number) indicates that different substances have different solubility in the same solvent.
21. (3 points) impossible task: 'there is a shallow layer of sodium hydroxide solution in a flat bottom shallow plate, and a coin is immersed in the solution at the bottom of the plate. It is required not to contact the solution and the shallow plate does not make any changes. Take out the coin by hand. Available equipment: candles (mainly containing carbon and hydrogen compounds), matches, large glasses. 'Xiao Ke, who loves challenge, has designed a method. The design drawing is as shown in the figure. Please explain its principle with scientific knowledge
22. (5 points) a chemical interest group explored whether 'NaOH solution reacts with dilute hydrochloric acid exactly and completely'. Please participate in their inquiry activities and answer the relevant questions. Known: sodium chloride solution is neutral copper chloride is soluble in water
[experimental exploration]
(1) Scheme 1: a student first adds about 2ml NaOH solution to the test tube, then drops a few drops of phenolphthalein solution, and the solution turns red. Then slowly drop in dilute hydrochloric acid, shake while dropping until the solution just becomes colorless, which proves that NaOH solution reacts with dilute hydrochloric acid exactly.
From the microscopic point of view, the essence of the reaction is.
In the process of dropping dilute hydrochloric acid, if a small number of bubbles have been observed, please analyze the possible causes of bubbles (just write one).
(2) Scheme II:
Conclusion of experimental steps and phenomena
Take 2ml NaOH solution to
Drop a certain amount into the test tube
Dilute hydrochloric acid of, add after oscillation
In case of excessive hydrochloric acid in magnesium strip
If there is no obvious phenomenon, NaOH solution reacts perfectly with dilute hydrochloric acid
[experimental reflection]
(3) Some students put forward scheme 2, which can not prove that NaOH solution reacts with dilute hydrochloric acid exactly and completely.
(4) In addition to the above scheme, which of the following substances can be used alone to complete the experiment? (Fill in the serial number).
A. PH test paper B. copper C. purple litmus test solution D. copper sulfate
2019 Beijing Xiangyu senior high school entrance examination three mode examination paper
Analysis of reference answers and test questions
1. Multiple choice questions (12 questions in total, Full Score: 12 points, 1 point for each question)
1. Fanchang kiln in Wuhu City is known as the birthplace of China 's blue and white porcelain. In the manufacturing process of ceramic ware, there must be chemical changes ()
A. Mix B. forming
C. Dry D. sintering
[analysis] chemical change refers to the change of new substance generation, physical change refers to the change of no new substance generation, and the essential difference between chemical change and physical change is whether there is new substance generation; according to this analysis, judge .
[answer] solution: A. there is no new substance generated in the mixing process, which belongs to physical change.
B. There is no new material formation in the forming process, which belongs to physical change.
C. There is no new material formation in the drying process, which belongs to the physical change.
D. The formation of new substances in the sintering process belongs to chemical change.
So choose: D.
[comment] it is not difficult to solve this problem. When you answer it, you need to analyze whether there are new substances generated in the process of change. If there are no new substances generated, it belongs to physical change. If there are new substances generated, it belongs to chemical change.
2. The following ancient poems contain the movement of molecules
A. Gold is not afraid of fire, wine is not afraid of alley
B. The wildfire is endless, and the spring wind blows again
C. Thousands of hammers chisel out the deep mountain, and the fire burns like idleness
D. I can 't sleep in spring and hear birds everywhere
[analysis] according to the molecular properties, the molecules are very small, moving constantly, and there is a gap between the molecules; the secret fragrance is that people smell the fragrance of flowers, which can be analyzed and considered from the perspective of molecular movement
[answer] solution: people can smell the strong fragrance of wine in the distance because the alcohol molecules contained in the strong fragrance of wine are constantly moving, spreading around, making people smell the fragrance of wine.
So: a.
[comments] this question is to examine the students 'application of the viewpoint of particles to explain some phenomena in daily life. Therefore, students should master the basic properties of particles and be able to explain some macro phenomena with the properties of particles.
3. The following descriptions of experimental phenomena are correct ()
A. Red phosphorus can burn in oxygen, not in air
B. Light blue flame when sulfur burns in oxygen
C. Fine wire burns in oxygen, sparks fly, and iron oxide is produced
D. The burning charcoal reaches into the cylinder containing oxygen and burns violently, giving off white light
[analysis] A. analyze and judge the burning phenomenon of red phosphorus in oxygen.
B. According to the phenomenon of sulfur combustion in oxygen, it is analyzed and judged.
C. According to the phenomenon of fine iron wire burning in oxygen, it is analyzed and judged.
D. According to the phenomenon of charcoal burning in oxygen, the paper analyzes and judges.
[answer] solution: A. red phosphorus can burn in oxygen, but not in air. It is a chemical property and not an experimental phenomenon, so the option is wrong.
B. Sulfur burns in oxygen, giving off a bright blue purple flame, producing a gas with an irritating odor, so the option is wrong.
C. The iron wire burns violently in oxygen, and Mars radiates a lot of heat. The formation of Fe3O4 is an experimental conclusion rather than an experimental phenomenon, so the option is wrong.
D. The burning charcoal extends into the gas cylinder containing oxygen, burns violently and emits white light, so the option is correct.
So choose: D.
[comment] it is not difficult to solve this problem. You can correctly understand the common phenomena of material combustion. When describing the phenomena of material combustion, you need to pay attention to the differences between light and flame, smoke and fog, experimental conclusions and experimental phenomena.
4. The following substances are oxides ()
AO3BSiO2
CCu2 (OH) 2CO3DFe (OH) 3
[analysis] this paper examines the identification of oxides. According to the concept of oxides, there are only two elements in oxides, and there must be oxygen.
[answer] solution: A. ozone only contains one element, which belongs to simple substance, so it does not meet the question;
B. There are two elements in silicon dioxide, one is oxygen, which belongs to oxide, so it fits the question;
C. There are four elements of carbon, hydrogen, oxygen and copper in basic copper carbonate, which belong to compound but not oxide, so it doesn 't accord with the topic;
D. Iron hydroxide contains three elements: iron, hydrogen and oxygen. It is a compound but not an oxide, so it does not meet the question.
So: B.
[comment] this topic is relatively simple. It mainly focuses on the key points of judgment from the concept. Two key points are indispensable and should be possessed at the same time.
5. Persimmon is one of the five major fruits in China. Its nutritional value is very high and rich in sucrose, vitamin C, iodine, calcium, phosphorus, iron and zinc, among which iodine, calcium, phosphorus, iron and zinc refer to ()
A. Element B. atom C. molecule D. ion
[analysis] according to the analysis of vitamin C, iodine, calcium, phosphorus, iron and zinc in food, medicine, fruit, nutrition, mineral water and other substances, they do not exist in the form of simple substance, molecule, atom and so on, but in the form of elements;
Answer: sucrose, vitamin C, iodine, calcium, phosphorus, iron and zinc in persimmon refer to elements;
So: a.
[comment] chemistry comes from production and life, and also serves production and life. The knowledge related to production and life is the focus of midterm examination over the years. In the process of learning, we should pay attention to the combination of theory and practice.
6. The detergent containing phosphorus contains na5p3o10, which will cause water pollution if widely used. The following statement about na5p3o10 is correct ()
A. Contains 5 oxygen molecules
B. architectural lighting companies The mass ratio of sodium and oxygen is 1: 2
C. There are two kinds of metal elements
D. The valence of phosphorus is + 5
[analysis] A. analyze and judge according to the microscopic composition of na5p3o10.
B. According to the ratio of the mass ratio of each element = the relative atomic mass of each atom the number of atoms in the compound, the analysis and judgment are carried out.
C. According to the meaning of chemical formula na5p3o10, analyze and judge.
D. According to the sum of positive and negative valence algebras in the compound is zero, analysis and judgment are carried out.
[answer] solution: a. na5p3o10 is made up of na5p3o10 molecules and does not contain oxygen molecules, so the option is wrong.
B. The mass ratio of sodium and oxygen is (23 5): (16 10) 1: 2, so the option is wrong.
C. Na5p3o10 contains sodium as a metal element, so the option is wrong.
D. Sodium element shows + 1 valence, oxygen element shows 2 valence. Let the valence of phosphorus element be X. according to the algebraic sum of positive and negative valence in the compound is zero, we can get: (+ 1) 5 + 3x + (2) 10 = 0, then x = + 5 valence, so the option is correct.
So choose: D.
[comment] the difficulty of this question is not very big. Check the students 'ability to analyze and solve problems by combining new information, flexibly using the meaning of chemical formula and relevant calculation.
7. The following washing methods mainly utilize the chemical properties of the substance ()
A. Wash the mobile screen with anhydrous alcohol B. wash the oil stains on the clothes with gasoline
C. Wash the salt on the clothes with clear water
[analysis] chemical properties of substances are properties that can only be displayed through chemical changes. Physical properties are properties that can be displayed without chemical changes, including color, state, odor, melting point, boiling point, density, solubility, etc. chemical properties generally include flammability, oxidation, stability, reduction, etc
[answer] solution: A. anhydrous alcohol can dissolve the stolen goods on the screen of the mobile phone. It is washed according to the principle of dissolution, so a does not meet the question;
B. Grease is not easy to dissolve in water and cannot be washed with water. It can be washed off with gasoline. It is washed according to the principle of dissolution, so B is not in line with the question;
C. Salt is easy to dissolve in water. It can be washed after dissolving in water. It is washed according to the principle of dissolving action, so C does not meet the question;
D. The scale is not easy to dissolve in water, but it can react with acid to form soluble salt. Therefore, vinegar can wash away the scale in the kettle by using the chemical properties of the substance, so D is in line with the question.
So choose: D.
[comment] to distinguish whether the properties of substances belong to physical properties or chemical properties, the key is to see whether the properties need to be displayed through chemical changes
8. The simple and feasible method to distinguish O2, CO and CO2 is ()
A. Put gas into clarified lime water respectively
B. Test the solubility of three gases in water
C. Put the burning wood into the bottle
D. Put the gas into the purple litmus test solution
[analysis] in order to identify the three gases of O2, CO and CO2, it is necessary to design three different experimental phenomena according to the different properties of the three gases, so as to achieve the purpose of identifying the three gases at one time .
[answer] solution: A. carbon dioxide can make the clarified lime water turbid. Only carbon dioxide can be identified with the clarified lime water, but not CO and oxygen, so the option is wrong.
B. It is difficult to test the solubility of three kinds of gas in water, and the operation is more complex. It can identify but is not the most commonly used method, so the option is wrong.
C. Put the burning wood strip into three gas cylinders respectively. If the wood strip goes out, it is carbon dioxide; if the wood strip burns more vigorously, it is oxygen; if the gas can burn, it is carbon monoxide; the phenomenon is obvious, it can identify the three gases at one time, so the option is correct.
D. When the purple litmus solution is respectively introduced, carbon dioxide can react with water to form carbonic acid. Carbonic acid can make the purple litmus solution turn red. Oxygen and carbon monoxide are unchanged. It is impossible to identify oxygen and carbon monoxide, so the option is wrong.
So choose: C.
[comments] this question examines the identification methods of common gases. The key to solving the problem is to use the difference of the nature of the gas to be identified and judge whether it can be identified according to whether there are obvious different phenomena in the experiment.
9. The unreachable purpose of the device as shown in the figure is ()
A. Remove sediment B. lighten colored water
C. Deodorize D. turn seawater into fresh water
[analysis] according to the analysis of the properties and functions of various materials during water purification, we can judge the relevant statements.
[answer] solution: A. pebble and quartz sand fluffy cotton in the water purification device can remove insoluble impurities and sediment, so a does not meet the question;
B. The activated carbon of the water purification device has the property of adsorption, which can absorb pigment and make the color of colored water lighter, so B is not in line with the question;
C. The activated carbon of the purified water device has the characteristics of adsorption, odor absorption and odor removal, so C does not meet the requirements;
D. The water purification device can not reduce the content of calcium and magnesium ion compounds in the water, and can not change the seawater into fresh water, so D is in line with the question.
So choose: D.
[comment] this question is relatively simple. To understand the principle of purified water and the nature of various materials is the basic knowledge to solve this question.
10. What 's inappropriate about the measures or statements of combustion and fire fighting
A. Cover the oil pan when it 's on fire to keep off oxygen
B. Cover the alcohol lamp with wet cloth to reduce its ignition point
C. Forest fires cut down trees to form a separation zone
D. In case of fire in the room, close the doors and windows in time
[analysis] combustible combustion needs to contact with oxygen and make the temperature reach the ignition point of combustible, and the method of isolating oxygen or reducing temperature can be adopted to extinguish the fire.
Answer: A. when the oil pan is on fire, use the cover to put out the fire. This is to cut off the oxygen and put out the fire, so it is correct;
B. The alcohol lamp is covered with a wet rag to extinguish the fire. This is to isolate the oxygen to extinguish the fire. The ignition point belongs to the property of combustibles and cannot be reduced, so it is wrong;
C. It is correct to cut down trees to form isolation zone to put out fire in case of forest fire;
D. When there is a fire in the room, close the doors and windows in time, otherwise the air will circulate and the fire will be more prosperous, which will cause the fire to spread rapidly and is not conducive to extinguishing the fire, so it is correct.
So: B.
[comment] to solve this problem, it is necessary to fully understand that the ignition point of combustible is an attribute of combustible itself, which cannot be changed in general.
11. There is a bottle of potassium nitrate saturated solution at t. The following statement is correct ()
A. It must be both a concentrated solution and a saturated solution
B. When the temperature increases, the mass fraction of solute decreases
C. When the temperature is reduced, crystals are precipitated, and the remaining solution is still saturated
D. At t, the mass fraction of solute increases with the addition of KNO3 solid
[analysis] potassium nitrate is a soluble substance, and the solubility of potassium nitrate increases with the increase of temperature. Saturated solution refers to a solution that can not continue to dissolve a certain solute in a certain amount of solvent at a certain temperature. It is called a saturated solution of this solute
[answer] solution: A. because we do not know the temperature and the solubility, we cannot judge the concentration of the solution, so a is wrong;
B. When the saturated solution of potassium nitrate is heated up, because the solubility of potassium nitrate increases with the increase of temperature, its saturated solution will become unsaturated solution, and the mass fraction of solute in the solution will not change, so B error ;
C. When the saturated solution of potassium nitrate is cooled, there will be crystal precipitation in the solution, but the solution is still saturated, so C is correct;
D. Since the potassium nitrate solution is a saturated solution at t, when the potassium nitrate is added, the potassium nitrate will not be dissolved again, so the mass fraction of the solute in the solution remains the same, so D is wrong;
So choose: C.
[comment] this question is very difficult. It mainly examines the changes of the amount that may be caused by cooling, warming and increasing solute of saturated solution under a certain temperature, so as to deepen students 'understanding of saturated solution
12. The following experiments can achieve the purpose ()
A. verify the combustion conditions of combustibles
B. measure the content of O2 in the air
C. check the existence of CO32
D. co absorption with water
[analysis] A. combustion conditions of combustibles: contact with oxygen, and the temperature reaches the ignition point of combustibles;
B. Carbon dioxide is produced by burning charcoal;
C. Carbonates and active metals can react with dilute hydrochloric acid to form carbon dioxide, hydrogen and other gases;
D. Carbon monoxide is insoluble in water.
[answer] solution: A. in the process of use, white phosphorus on copper sheet burns, red phosphorus cannot burn, which means that it can only burn when the temperature reaches the ignition point of combustibles, and white phosphorus in water cannot burn, which means that oxygen is needed for combustion, and this option can achieve the experimental purpose;
B. The combustion of charcoal produces carbon dioxide gas, and the volume of oxygen consumed is occupied by carbon dioxide, so that water cannot enter the gas collecting cylinder, so that the content of oxygen in the air cannot be measured. This option cannot achieve the experimental purpose;
C. When dropping hydrochloric acid to produce bubbles, it can 't be said that there is carbonate ion in the solid. This is because the more active metal, such as zinc, can react with dilute hydrochloric acid to generate gas and generate bubbles. This option can 't achieve the experimental purpose;
D. Carbon monoxide is insoluble in water, so it can 't be absorbed by water. This option can' t achieve the experimental purpose.
So: a.
[comment] experimental phenomena are the external manifestation of the interaction between substances. Therefore, we should learn to design experiments, observe experiments and analyze experiments, so as to lay a foundation for revealing the essence of the interaction between substances.
2. Answer questions (10 questions in total, 33 points in total)
13. (3 points) chemistry is closely related to our production and life.
(1) Fill in the corresponding space with the letter number of the following substances:
a. Salt water B. vitamin C. liquid oxygen D. hydrated lime E. graphite
D can be used to neutralize acid soil in agriculture;
E can be used to make pencil lead;
B is the main nutrient in vegetables;
It is C that can be used as combustion supporting agent for rocket launching.
(2) Energy and environment are issues that we are increasingly concerned about. To protect the environment and control pollution, we need the whole society to act together.
The three major fossil fuels include coal, oil and natural gas. Scientists have found combustible ice on the sea floor. Its main composition is the same as that of natural gas and biogas. Its chemical formula is CH4.
Coal mainly contains carbon elements. Using coal as fuel, it mainly uses the heat generated by the reaction of carbon elements and oxygen, and generates carbon oxides at the same time. When the oxygen is insufficient, it will generate a kind of air pollution gas Co.
In view of the increasingly serious environmental problems, the following relevant practices are not conducive to environmental protection: C (fill in alphabetic number).
A. Develop green transportation and promote public travel B. try to use degradable plastics to reduce white pollution
C. Domestic waste is poured into river D. waste batteries are recycled to save resources and reduce environmental pollution
[analysis] (1) the nature of the substance determines the use of the substance, and it can be analyzed and solved according to the nature of the existing substance;
(2) analyze according to the types and main components of fossil fuels;
According to the products of incomplete combustion of carbon fuel;
Analyze and solve problems according to the knowledge of environmental protection.
Solution: (1) hydrated lime is alkaline and can be used to improve acid soil;
Therefore, fill in: D;
Graphite is very soft and can be used to make pencil lead;
Therefore, fill in: e;
The main nutrients in vegetables are vitamins;
Therefore, fill in: B;
Oxygen has combustion supporting property and can be used as combustion supporting agent for rocket launching;
Therefore, fill in: C;
(2) fossil fuels include coal, oil and natural gas, all of which are non renewable energy; the main component of natural gas and biogas is methane, so it is filled with: oil; CH4;
When the fuel containing carbon element burns under the condition of insufficient oxygen, it will generate toxic carbon monoxide;
A. developing green transportation, promoting public travel and driving less private cars can reduce NOx emissions and contribute to environmental protection;
B. The use of degradable plastics can reduce 'white pollution', which is beneficial to environmental protection;
C. The domestic garbage will pollute the water source when it is poured into the river, which is harmful to the environmental protection;
D. Recycling waste batteries, saving resources and reducing environmental pollution are beneficial to environmental protection.
So fill in: C.
[comments] this question mainly examines the nature and use of substances, the types of fossil fuels, environmental protection, etc., which belongs to basic knowledge and is not difficult. It can be solved according to the existing knowledge.
14. (3 points) Figure 1 is a network diagram of metal chemical properties summarized by a student. Fig. 2 and Fig. 3 are experiments on the chemical properties of metals.
(1) The substance of X in Figure 1 belongs to acid.
(2) The experimental phenomenon in Figure 2 is that the iron wire burns violently, releases heat, and generates black solid matter.
(3) Fig. 3 experiment: tubes and are filled with iron powder, and a certain amount of zinc chloride solution and copper chloride solution are added respectively. After full reaction, all the substances in tubes and are poured into the same beaker. It is found that the red solid substances in the beaker increase significantly. The following statement is correct: a.
A. Figure a tube there must be only copper in the solid after reaction
B. Figure B there must be no iron in the solid of beaker
C. Figure B the beaker liquid must contain Zn2 +, Fe2 +, Cu2 +
(4) The chemical equation 3Co + Fe2O3 2Fe + 3co2 for the reduction of iron oxide by carbon monoxide in the laboratory is given.
[analysis] (1) analyze the substance category of X according to the properties of metal.
(2) According to the phenomenon of iron combustion in oxygen;
(3) According to the reaction analysis of metal and salt solution to judge the relevant statement;
(4) According to the principle of reducing iron oxide with carbon monoxide in the laboratory, the chemical equation of the reaction is written.
[answer] solution: (1) according to the properties of metals, metals can react with acids in addition to oxygen and salt, so the substance of X in Figure 1 belongs to acids.
(2) The experiment in Figure 2 shows that the iron wire burns in oxygen. The phenomenon is that the iron wire burns violently, releases heat, and generates black solid substance.
(3) The sequence of activity of the three metals is zinc> iron> copper, so iron will not react with zinc chloride, iron will replace copper in copper chloride, and all the substances in test tubes and will be poured into the same beaker . After full reaction, it is found that the red solid substances in the beaker increase significantly, indicating that iron will replace copper in copper chloride, iron completely reacts, Copper sulfate has surplus, so:
A. It can be seen from the above analysis that the iron in tube of figure a completely participated in the reaction, and there must be only copper in the solid after the reaction, so a is correct;
B. According to the above reaction phenomenon, it can not be determined whether there is iron in the beaker solid of figure B, so error B
C. Through the above reaction, it can be determined that the beaker liquid in Figure B must contain Zn2 +, Fe2 +, and Cu2 +, so C error.
(4) The chemical equation of the reaction is: 3Co + fe2o32fe + 3co2.
So the answer is: (1) acid; (2) black solid substance; (3) a; (4) 3Co + Fe2O3 2Fe + 3co2.
[comment] it is a hot topic to examine the nature of common metals, the comparison of metal activity, the sequence and application of metal activity, and the analysis of experimental phenomena and results, which should be paid attention to.
15. (3) with the development of economy, energy and environment have become the focus of attention
(1) Coal, natural gas and oil are usually called fossil fuels. When coal is used for power generation, the purpose of pulverizing coal into pulverized coal is to increase the contact area
(2) At present, the energy consumed by human beings mainly comes from fossil fuels. The largescale use of fossil energy willproduce SO2, Co, NO2, CO2 and other gases and dust, among which the content in the atmosphere keeps rising, leading to the enhancement of greenhouse effect. The global warming is CO2, and the formation of acid rain is SO2 (or NO2) (only one is written)
(3) Hydrogen energy is a kind of new energy which is both efficient and clean. Fuel cell vehicles using hydrogen as energy are very popular. The chemical equation 2h2 + O2 2H2O of hydrogen fuel is written
(4) Nuclear energy is also a kind of efficient energy. The development of deuterium nuclear energy is considered as one of the main ways to solve the problems of energy and environment in the future. It is known that deuterium hydrogen belongs to the same element , so the number of protons in deuterium nucleus is 1
(5) When a purification device is installed on the automobile exhaust pipe, the carbon monoxide and nitric oxide gas in the exhaust gas react on the catalyst surface, producing two nontoxic gases. The chemical equation of the reaction is 2CO + 2No 2 + 2CO 2
[analysis] (1) according to the conditions of the three major fossil fuels and fuels and the methods to make the combustion more sufficient;
(2) Carbon dioxide is a major greenhouse gas, and sulfur dioxide and nitrogen oxides are important substances for the formation of acid rain;
(3) First, find out the reactant, product and reaction condition according to the reaction principle, and write according to the writing method and steps of chemical equation
(4) Element is the general name of a kind of atom with the same nuclear charge or proton number, so the same proton number of element must be the same, so we can answer the question accordingly
(5) Before and after the reaction, the type of elements and the total number of atoms remain unchanged
[answer] solution: (1) the three major fossil fuels are coal, natural gas and oil. When coal is used for power generation, the coal block is crushed into coal powder, the purpose of which is to increase the contact area with oxygen and make the combustion more full. Therefore, the answer is: increase the contact area with oxygen and make the combustion more full; therefore, fill: oil; increase the contact area;
(2) The content of carbon dioxide in the atmosphere keeps rising, which leads to the enhancement of greenhouse effect and global warming. Sulfur dioxide and nitrogen dioxide can react with water to form acid substances. When the acidity of rainwater reaches a certain degree, ie pH <5.6, acid rain will be formed. Therefore, filling: CO2; SO2 (or NO2);
(3) The chemical equation of the reaction is: 2h2 + O2 2H2O;
(4) Element is the general name of the same kind of atoms with the same nuclear charge or proton number, so the same proton number of element must be the same, so deuterium belongs to one of the hydrogen elements, so the number of protons in deuterium nucleus is 1;
(5) Carbon monoxide and nitric oxide contain carbon element, nitrogen element and oxygen element. The reaction can produce two nontoxic substances. The two substances should be carbon dioxide and nitrogen. The chemical equation of the reaction is: 2CO + 2no2 + 2co2. Therefore, 2CO + 2no2 + 2co2
[comment] this question is about the examination of energy related issues, mainly about the analysis of new energy knowledge, which belongs to the basic knowledge examination
16. (5 points) read the following popular science essay.
Distilled wine is a kind of wine which is produced by 'fermentation and re distillation' of grain. Chinese liquor is distilled liquor with sorghum, wheat and other grains as raw materials. Spirits above 40 degrees are mostly distilled spirits. According to Li Shizhen ' s Compendium of Materia Medica, 'wine cooking is not an ancient method. It was created in Yuan Dynasty.'.
The 'degree' of Liquor refers to the volume percentage of alcohol (ethanol) in liquor at room temperature. '53 degrees' means that there are 53 ml of alcohol in 100 ml of alcohol.
Chinese people drink white wine, there is an important indicator, called 'taste mellow', generally measured by 'viscosity', the greater the viscosity, the mellower the taste. 'Viscosity' depends on the type of molecules in the liquid and the attraction between them. The viscosity of wine mainly depends on the proportion of water and alcohol molecules. The relationship between alcohol degree and alcohol viscosity shows a curve, as shown in Figure 1.
No matter what brand of wine, more than 98% of its ingredients are water and alcohol. The flavor difference of different wines comes from 2% of other ingredients, such as aldehydes, esters and aromatic. The composition proportion of the wine is shown in Figure 2.
Alcohol can be absorbed in the mouth, stomach and small intestine. After absorption, only 10% of alcohol is excreted through respiration and urination, and the remaining 90% of alcohol reaches your liver for metabolism. The liver is like a large chemical factory, which has many channels to help the transformation of alcohol.
Acetaldehyde after alcohol transformation is toxic, which can destroy the structure of some proteins in the body, and has a great impact on the liver and pancreas. Alcohol is also toxic. Its longterm effect is toxic to the brain. After entering the body, the alcohol can reach the brain in 10 minutes, and it will stay in the brain for half a month to a month.
China is a big country of drinking. The number of people who are addicted to alcohol or alcohol has reached 200 million. The rate of chronic alcoholism has been increasing year by year.
Answer the following questions:
(1) '40 degree' liquor means that in 100ml liquor, it contains 40ml alcohol.
(2) Fig. 1 is a curve chart of the influence of alcohol degree on the viscosity of wine. It can be concluded that when the alcohol degree is lower than 55.9, the viscosity of wine increases with the increase of degree. When the alcohol degree is higher than 55.9, the viscosity of wine decreases with the increase of degree.
(3) It is speculated that the elements in ethanol, acetaldehyde and acetic acid must be carbon and hydrogen.
(4) The original pulp of Maotai liquor after fermentation and distillation is about 60 degrees. It needs to be aged for more than three years before it is put on the market for sale. At this time, the degree of Maotai liquor is less than 60 degrees (fill in 'more than' or 'less than').
(5) The following statement is correct for ade.
A. Chemical changes must have taken place in the process of wine brewing. B. The higher the degree, the better the taste. C. The price of different brands of wine varies greatly because of the different main ingredients. D. Drink a little to make you happy. Drink too much to hurt you. Don 't drink or drive. E. Ethanol solution can be used for medical disinfection.
[analysis] (1) analyze according to the meaning of 'degree' of liquor;
(2) Analyze according to the diagram information;
(3) According to the law of mass keeping constant;
(4) Analysis according to the volatility of alcohol;
(5) According to the principle of wine making, the information of dry matter, the properties and uses of alcohol.
[answer] solution: (1) 'degree' of Liquor refers to the volume percentage of alcohol (ethanol) in liquor at room temperature, so '40 degree' Liquor refers to 40 ml alcohol in 100 ml liquor. Therefore: 40;
(2) According to the influence curve of alcohol degree on liquor viscosity, when alcohol degree is lower than 55.9, liquor viscosity increases with the increase of alcohol degree, and when alcohol degree is higher than 55.9, liquor viscosity decreases with the increase of alcohol degree; therefore, when alcohol degree is lower than 55.9, liquor viscosity increases with the increase of alcohol degree, and when alcohol degree is higher than 55.9, liquor viscosity decreases with the increase of alcohol degree;
(3) According to the diagram, the final product is carbon dioxide and water. According to the law of conservation of mass, ethanol, acetaldehyde and acetic acid must contain carbon and hydrogen;
(4) Alcohol is more volatile than water, so the original pulp of Maotai liquor after fermentation and distillation is about 60 degrees, which needs to be stored for more than three years before it is put on the market for sale. At this time, the alcohol degree is less than 60 degrees;
(5) A. in the process of wine brewing, there are new substances generated, which must have chemical changes, correct.
B. Generally, it is measured by 'viscosity'. The bigger the viscosity is, the mellower the taste is. It is not that the higher the degree is, the better the taste is. It is wrong.
C. The price of different brands of wine varies greatly. The main ingredients are water and alcohol. The taste difference of different wines comes from 2% of other ingredients, such as aldehydes, esters and aromatics. It 's wrong.
D. It 's right not to drink and drive.
E. Ethanol solution can be used for medical disinfection, correct.
So: ade.
[comment] this question is about the knowledge of chemistry and life. It can be completed according to the existing knowledge.
17. It is a complex process to turn iron from iron ore. The iron ore, coke and limestone are added into the blast furnace together. At high temperature, the iron is reduced from the iron ore by using the carbon monoxide generated by the reaction in the furnace. As shown in the figure.
(1) Main chemical reactions in blast furnace:
C + CO2 2CO
Carbon monoxide reduces iron oxide 3Co + Fe2O3 2Fe + 3co2.
(2) The blast furnace gas must contain Co, CO2 and N2.
An interest group simulated the chemical principle of ironmaking in the laboratory, reduced iron oxide powder with carbon monoxide, and designed a and B sets of experimental devices respectively.
(3) To clarify the cause of lime water turbidity (expressed by chemical equation) CO2 + Ca (OH) 2 = CaCO3 + H2O.
(4) From the perspective of environmental protection and energy conservation, you think device B (fill in the serial number) is more reasonable.
[analysis] (1) analyze according to the principle of chemical reaction;
(2) According to the composition of tail gas;
(3) According to the nature of carbon dioxide and the writing method of chemical equation;
(4) Analyze according to the characteristics of the device.
[answer] solution: (1) under the condition of high temperature, carbon monoxide reacts with iron oxide to form iron and carbon dioxide;
(2) The reaction in blast furnace is that carbon and oxygen produce carbon dioxide, carbon dioxide and carbon react to produce carbon monoxide as reducing agent, iron oxide is reduced to produce iron, blast furnace gas is mainly carbon monoxide, carbon dioxide and nitrogen , etc., the blast furnace gas produced in the process of ironmaking must contain the following components: CO, CO2, N2, etc .; therefore, filling: CO, CO2, N2;
(3) Carbon dioxide reacts with calcium hydroxide to form calcium carbonate white precipitate and water, so filling: CO2 + Ca (OH) 2 = CaCO3 + H2O;
(4) Unit B reuses the tail gas after treatment, which not only saves energy, but also protects the environment.
[comments] this paper comprehensively examines the chemical reaction of carbon monoxide reducing iron oxide and the writing of chemical equation.
18. (4 points) for the following four sets of common experimental devices, please fill in the following relevant blanks as required:
(1) In Figure 1, the experiment is to use the combustible to consume the oxygen in the cylinder and reduce the pressure in the cylinder to speculate the oxygen content in the air.
(2) Figure 2 in the experiment, the function of water is to absorb sulfur dioxide and prevent it from polluting the air.
(3) Fig. 3 the phenomenon that can be seen in the experiment is the intense burning, the Mars shooting, and the formation of a black solid.
(4) Fig. 4 during the experiment, the gas produced in tube 1 is hydrogen (fill in the name).
(5) In the above four experiments, the experiments to study the composition of substances are shown in Fig. 1 and Fig. 4.
[analysis] (1) analyze the answer according to the principle of measuring oxygen volume fraction in air;
(2) Analyze and answer according to the precautions of sulfur combustion in oxygen;
(3) According to the phenomenon of iron wire burning in oxygen;
(4) According to the phenomenon and conclusion of electrolyzed water, the answer is analyzed;
(5) According to the process and purpose of the experiment, we can analyze and judge the answer.
[answer] solution: (1) the experiment in Figure 1 uses the combustible red phosphorus to burn the oxygen in the cylinder, and generates a solid to reduce the pressure in the cylinder to speculate the oxygen content in the air.
(2) In Figure 2, sulfur dioxide is generated by sulfur combustion, which can pollute the air. The function of water is to absorb sulfur dioxide and prevent it from polluting the air.
(3) Fig. 3 the experiment is that the iron wire burns in the oxygen. The visible phenomenon is that the iron wire burns violently, and sparks are everywhere, forming a kind of black solid.
(4) Fig. 4 during the experiment of electrolyzing water, the gas produced in tube 1 is mostly hydrogen.
(5) In the above four experiments, figure 1 can determine the composition of air, and Figure 4 can determine the composition of water.
The answer is: (1) the pressure decreases;
(2) Absorb sulfur dioxide to prevent air pollution;
(3) It burns violently, sparks are everywhere, forming a kind of black solid;
(4) Hydrogen;
(5) Figures 1 and 4.
[comments] all the experiments examined in this question are basic experiments in textbooks, which are not very difficult. Therefore, we should strengthen the study of experiments and improve the ability of experiments.
19. (4 points) as shown in the figure, it is a common device for gas production in the laboratory.
(1) Write out the chemical equation of oxygen production with a device: 2h2o22h2o + O2.
(2) When heating solid ammonium bicarbonate, the following reaction will take place: nh4hco3nh3 + H2O + CO2. If the reaction is to be used to generate carbon dioxide and a bottle of pure carbon dioxide is collected by e device, the order of the selected device conduit connection from left to right is: a D e F. at the same time, please complete the conduit in E device.
[analysis] (1) the preparation device includes heating and no heating. If hydrogen peroxide and manganese dioxide are used to produce oxygen, no heating is needed; if potassium permanganate or potassium chlorate is used to produce oxygen, heating is needed. The density of oxygen is higher than that of air, and it is not easy to dissolve in water, so it can be collected by the method of upward air discharge and drainage.
(2) When heating solid ammonium bicarbonate, the following reactions will take place: nh4hco3nh3 + H2O + CO2. To produce carbon dioxide with this reaction and collect a bottle of pure carbon dioxide with e device, the ammonia gas should be removed with concentrated sulfuric acid and dried.
[answer] solution: (1) if hydrogen peroxide and manganese dioxide are used to make oxygen, there is no need to heat it. Hydrogen peroxide generates water and oxygen under the condition of manganese dioxide as catalyst, and attention should be paid to balance ; therefore, the answer is: 2h2o2 2H2O + O2;
(2) The following reactions occur when heating solid ammonium bicarbonate: NH4HCO3 NH3 + H2O + CO2, if you want to use this reaction to produce carbon dioxide, and use e device to collect a bottle of pure carbon dioxide, you should use concentrated sulfuric acid to remove ammonia and dry it; at the same time, the density of CO2 is larger than air, use the upward air method to collect, and CO2 should be from a long pipe into a human gas cylinder; so the answer is: DE ;
[comments] this test point mainly examines the selection of gas preparation and collection devices, as well as the writing of chemical equations and the removal of impurities, etc., which are relatively comprehensive. The selection of gas preparation device is related to the state of reactant and reaction conditions; the selection of gas collection device is related to the density and solubility of gas. This test point is one of the important test points in the middle school entrance examination, which mainly appears in the experimental questions.
20. (2 points) the following experiments explore the factors affecting the solubility of substances. Experimental phenomena:
Almost insoluble in a
Solid soluble in B
The solid in C is soluble.
Phenomenon (fill in the serial number) indicates that different substances have different solubility in the same solvent.
[analysis] according to the explanation that different substances have different solubility in the same solvent, it is necessary to control the different types of solutes and the same types of solvents, and analyze and answer.
[answer] solution: it shows that different substances have different solubility in the same solvent. It should be controlled that the types of solutes are different and the types of solvents are the same. Then the phenomenon shows that different substances have different solubility in the same solvent.
So the answer is:
I 'm sorry.
[comment] the difficulty of this question is not great. Understanding the factors that affect the solubility of substances (the nature of solute and solvent, etc.) is the key to solve this question correctly.
21. (3 points) impossible task: 'there is a shallow layer of sodium hydroxide solution in a flat bottom shallow plate, and a coin is immersed in the solution at the bottom of the plate. It is required not to contact the solution and the shallow plate does not make any changes. Take out the coin by hand. Available equipment: candles (mainly containing carbon and hydrogen compounds), matches, large glasses. 'Xiao Ke, who loves challenge, has designed a method. The design drawing is as shown in the figure. Please explain its principle with scientific knowledge
[analysis] according to the combustion of oxygen in the air between the candle and the inverted beaker, carbon dioxide and water are generated. Carbon dioxide reacts with sodium hydroxide solution to generate sodium carbonate and water, and the analysis solution is carried out.
[answer] solution: the candle burns with the oxygen in the air in the inverted beaker to generate carbon dioxide and water. Carbon dioxide reacts with sodium hydroxide solution to generate sodium carbonate and water, reducing the pressure in the beaker. The sodium hydroxide solution at the bottom of the plate is sucked into the beaker and coins are taken out.
So the answer is:
The candle burns to generate carbon dioxide gas, and carbon dioxide reacts with sodium hydroxide solution to generate sodium carbonate and water, reducing the pressure in the beaker, and the sodium hydroxide solution at the bottom of the plate is sucked into the beaker.
[comment] it is not difficult to solve this problem. The key to solve this problem is to master that alkali can react with nonmetallic oxides to generate salt and water and reduce the pressure in the beaker.
22. (5 points) a chemical interest group explored whether 'NaOH solution reacts with dilute hydrochloric acid exactly and completely'. Please participate in their inquiry activities and answer the relevant questions. Known: sodium chloride solution is neutral copper chloride is soluble in water
[experimental exploration]
(1) Scheme 1: a student first adds about 2ml NaOH solution to the test tube, then drops a few drops of phenolphthalein solution, and the solution turns red. Then slowly drop in dilute hydrochloric acid, shake while dropping until the solution just becomes colorless, which proves that NaOH solution reacts with dilute hydrochloric acid exactly.
From the microcosmic point of view, the essence of the reaction is the formation of water by hydrogen ions and hydroxyl ions.
In the process of dropping dilute hydrochloric acid, if a small number of bubbles have been observed, please analyze the reason for the bubbles may be that NaOH reacts with CO2 in the air to generate sodium carbonate (just write one).
(2) Scheme II:
Conclusion of experimental steps and phenomena
Take 2ml NaOH solution to
Drop a certain amount into the test tube
Dilute hydrochloric acid of, add after oscillation
If there is any bubble in the magnesium bar, dilute hydrochloric acid will be excessive
If there is no obvious phenomenon, NaOH solution reacts perfectly with dilute hydrochloric acid
[experimental reflection]
(3) Some students put forward scheme 2, which can 't prove that NaOH solution reacts with dilute hydrochloric acid exactly. The reason is that if the amount of dilute hydrochloric acid is insufficient, there is no obvious surplus of sodium hydroxide.
(4) In addition to the above scheme, which of the following substances can be used alone to complete the experiment? AC (fill in the serial number).
A. PH test paper B. copper C. purple litmus test solution D. copper sulfate
[analysis] (1) analyze according to the essence of neutralization reaction;
Answer according to the chemical properties of sodium hydroxide;
(2) Analyze according to the chemical properties of dilute hydrochloric acid;
(3) The analysis is based on the chemical properties of alkali;
(4) According to the chemical properties of acid, alkali and salt.
[answer] solution: (1) from the microscopic point of view, the essence of neutralization reaction is the formation of water by hydrogen ions and hydroxyl ions;
When reacting with hydrochloric acid, there are bubbles, which are likely to be CO2. Then the reason of sodium hydroxide deterioration can be found out: NaOH reacts with CO2 in the air to generate sodium carbonate;
(2) Magnesium reacts with hydrochloric acid to produce magnesium chloride and hydrogen;
(3) Drop a certain amount of dilute hydrochloric acid into the NaOH solution, add magnesium strip after shaking, if there is no obvious phenomenon, it may be that the NaOH solution reacts with dilute hydrochloric acid exactly, or the amount of dilute hydrochloric acid exactly is insufficient, and there is residual sodium hydroxide;
(4) PH value The test paper measures the pH value of the solution. If it is 7, it will react. If it is less than 7, there is surplus acid. If copper does not react with dilute hydrochloric acid, it cannot be tested. If litmus test solution is dripped, litmus test solution turns red, indicating excessive hydrochloric acid. If litmus test solution does not change red, it means that hydrochloric acid just reacts completely. If hydrochloric acid and copper sulfate solution do not react, there is no obvious phenomenon. So AC is chosen.
The answer is: (1) hydrogen and hydrogen ions generate water; NaOH reacts with CO2 in the air to generate sodium carbonate;
(2) There are bubbles emerging;
(3) If the amount of dilute hydrochloric acid is insufficient, there is no obvious phenomenon of sodium hydroxide surplus;
(4) AC.
[comments] combined with textbook knowledge and experimental skills, the paper examined the students 'ability to analyze and solve problems. This question is comprehensive. It is a good comprehensive question to find out the students' ability to combine theoretical knowledge with experiments and to examine the students 'innovation ability.
