Xuzhou Twenty-sixth Middle School
Fill-in-the-blank questions are one of the questions that must be examined every year, accounting for about twenty percent, mainly examining students' mastery of basic theories and basic concepts and application, the form of the examination is mainly from the following aspects:
One, the writing and meaning of the chemical terminology. Such topics require students to understand and memorize the chemical terms on the basis of accurate expression, especially on the examination of chemical equations, is all-round, multi-angle, no matter how to change, as long as you master the principles of writing and steps, you can accurately write out.
1 (2007 Wuxi City), fill in the blanks with numbers and chemical symbols:
(1) chlorine atoms; (2) 2 sodium ions; (3) 3 carbon dioxide molecules;
(4) -2 valence of sulfur; (5) the smallest particles of water to maintain the chemical properties of water .
2 (2007 Wuxi City), in the "quicklime, alum, calcium carbonate, stainless steel, polyethylene, soda ash" in the appropriate choice of substances to fill in the blanks.
(1) used in the manufacture of medical equipment, cooking utensils; (2) used as a food desiccant;
(3) used in the paper, textile industry salt; (4) used as a calcium supplement salt;
(5) belong to the organic polymer compounds; (6) can be used as flocculating agent when purifying water is.
3 (2007 Wuxi City), the existing Na, O, C, H, four elements, please choose one or more of these elements to write a chemical formula that meets the following requirements write one of each:
(1) the most desirable fuels; (2) the volume fraction of the air accounted for the second gas;
(3) the soda contained in the unstable acid; (4) the main ingredient of the baking powder baking soda .
4 (2007 Wuxi City), write the chemical equations for the following reactions and indicate the basic type of reaction in parentheses:
(1) Hydrogen peroxide mixed with manganese dioxide to make oxygen , ( ) reaction;
(2) Iron wire burns in oxygen , ( ) reaction;
(3) Copper wire is immersed in silver nitrate solution;
(4) Magnesium in carbon dioxide Combustion in carbon dioxide produces magnesium oxide and carbon black .
5 (2007 Changzhou City), (1) Write the name, common name or chemical formula of the following substances.
Name Calcium oxide Sodium carbonate
Common name Mercury Lime
Chemical formula Hg Na2CO3
(2) Write the following chemical equations:
① Electrolysis of water to produce hydrogen gas: ;
② Zengqing (CuSO4) to iron to copper: .
6 (2006 Changzhou City), (1) write the chemical formula of the following substances:
① ferrous ions _____________________; ② aluminum sulfate ____________________.
(2) Chemical reactions have played a very important role in production from ancient times to the present. Write the chemical equations as required:
① Ancient wet copper refining ___________________________________________________;
② Industrial iron refining with hematite ore _______________________________________________.
7 (Changzhou City, 2005), write the chemical equations for the following reactions as required:
(1) Add a small amount of manganese dioxide _____________________________________________ to hydrogen peroxide.
(2) Zinc grains react with hydrochloric acid _________________________________________________________.
(3) Sulfuric acid reacts with sodium hydroxide _____________________________________________________.
(4) Glucose (C6H12O6) is slowly oxidized in the body ______________________________________.
Of the above reactions, the one that is a decomposition reaction is ________ and the one that is a replacement reaction is ________. (fill in the serial number)
8 (Nantong, 2006), this year, four cities in northern Jiangsu Province began to promote the use of ethanol gasoline. The decomposition of glucose (C6H12O6) produced by fermentation of crops can be used to obtain ethanol. Glucose is an organic matter composed of three elements, of which the element with the highest mass fraction is _________. Glucose is decomposed into ethanol and another common gas under the action of alcoholizing enzyme, which is .
9 (2006 Nantong), particle size to the nanometer scale of the single iron has a strong reaction activity, commonly known as "nano-iron".
(1) in high temperature conditions, with H2 and FeCl2 reaction, can produce "nano-iron" and a dissolved in water show strong acidic gas, write the reaction of the chemical equation .
(2) "nano-iron" in the air will burn on impact, the reaction is the same as iron in pure oxygen combustion, write the reaction of the chemical equation .
(3) Predict the other chemical properties of iron nanoparticles and express them as chemical equations.
10 (2007 Suzhou), in order to gasoline engine exhaust in the NO into N2, under the action of a catalyst with NH3 and NO reaction, the chemical equation is: 4NH3 + 6NO=====5N2 + 6H2O; in the usual conditions, based on the left before and after the order of the reactant and the product of the stoichiometric number of gases in the ratio = .
11 (2006 Nantong), "green chemistry" emphasizes the adoption of effective measures to prevent damage and pollution of the environment.
(1) sulfur combustion in oxygen before the experiment, to the gas cylinder, add appropriate amount of NaOH solution, and then carry out the experiment, the reason is (expressed by chemical equation) .
(2) in the car exhaust pipe on the installation of a "catalytic converter", can make the car exhaust in the NO and CO reaction, to generate can participate in the atmospheric ecological cycle of the two non-toxic gases. NO and CO reaction of the chemical equation for .
12 (2005 Xuzhou City), Through the study of chemistry, we have recognized many chemical reactions. Please answer the following questions with chemical equations.
(1) The reason for not using an iron bucket to hold copper sulfate solution .
(2) Painting walls with milk of lime creates hard walls .
(3) It is convenient, fast and environmentally friendly to make oxygen from hydrogen peroxide in the laboratory
13 (Zhenjiang City, 2007), (4 points) In chemical terms:
① elemental nitrogen ② 2 molecules of hydrogen ③ 3 ions of magnesium ④ iron sulphate
14 (Zhenjiang City, 2007), (2 points) CH4, the main component of natural gas, is also a gas that causes the greenhouse effect gas. It is known that for the same number of molecules of CH4 and CO2, the greenhouse effect caused by CH4 is more obvious, then for the same mass of the above two gases, the one that produces the greenhouse effect is more obvious .
15 (2007 Zhenjiang City), calcium oxalate (CaC2O4) is a deposit that cannot be absorbed by the body. Tofu contains more calcium salts [such as calcium sulfate (CaSO4), etc.], spinach, onions, bamboo shoots are rich in oxalic acid (H2C2O4), sodium oxalate (Na2C2O4) tofu and
The above kinds of vegetables mixed consumption, may induce "stone" disease.
(1) by the chemical formula of oxalic acid can be known which the valence of the carbon element is ;
a. (2) oxalic acid and calcium sulfate reaction of the chemical equation for H2C2O4 ten CaSO4 == CaC2O4↓ ten H2SO4 please write the chemical equation of sodium oxalate and calcium sulfate reaction .
Two, the nature and use of common substances. This kind of topic is usually closely linked with production, life practice, which requires students to understand and memorize the nature and uses of common substances, and in life, production, more observation and more thinking, will learn to link the knowledge and production, life practice, learn to think, learn to apply.
16 (2007 Changzhou City), (1) factors affecting the nature of substances are: A. different types of ions; B. different composition of molecules; C. different mass fractions of solutes, etc., please choose from the following factors leading to differences in the nature of substances (fill in the serial number).
①Carbon monoxide is flammable while carbon dioxide is not: ;
②FeSO4 is green while Fe2(SO4)3 is yellow: ;
③Concentrated sulfuric acid is hygroscopic while dilute sulfuric acid is not: .
(2) Write the chemical formula of the substance (or its main component) that has the following uses. Choose from the following:
Methane, table salt, slaked lime, oxygen, ammonium bicarbonate, limestone
① can be used as a fuel;
② can be used as a fertilizer;
③ can be used as a condiment;
④ can be used as a rocket accelerator .
17 (2006 Changzhou City),, (4 points) Some substances we learned in junior high school chemistry have important uses in real life. The following four substances are available: potassium nitrate, dilute sulfuric acid, copper sulfate, and dry ice, fill in the blanks with their (or their main components') chemical formulas.
(1) It can be used to prepare the fungicide Bordeaux _______________
(2) It can be used to remove rust _______________
(3) It can be used for artificial rainfall _______________
(4) It can be used as compound fertilizer _______________
18 (2005 Changzhou City), (5 points) in formaldehyde, ceramics, rubber, ammonium bicarbonate, ethanol, slaked lime, marble, potassium nitrate and other eight substances, commonly used to improve acidic soil is __________, commonly used as a dip in the preparation of taxidermy animals is __________, as ammonium nitrogen fertilizer in agriculture is __________, which can be used as automobile fuel instead of gasoline is __________, and which belongs to inorganic non-metallic materials is __________. (Choose the name of one substance for each blank)
19 (2005 Xuzhou City), Chemistry is all around us and it can improve our lives. Please choose from "A. oxygen B. nitrogen C. quicklime D. slaked lime E. vinegar F. urea G. stainless steel H. polyethylene" to fill in the blanks (fill in the letter).
(1) the rescue of critically ill people is commonly used substances; (2) used for crop fertilizers are substances;
(3) commonly used as bags of food desiccant is; (4) kitchen condiments pH less than 7 is;
(5) can be made into food bags is; (6) can be used for the manufacture of cutlery substances are;
20 (2006) (Nantong),, In industrial and agricultural production and daily life, chemical substances have a wide range of uses. Please fill in the blanks with the chemical formula choices of the following substances: helium, nitrogen, calcium oxide, hydrochloric acid, nitric acid, ferrous sulfate.
1) The rare gas that can be used to replace hydrogen as a sounding balloon is .
(2) The acid that can be used to produce explosives, dyes, and reacts with metals in a way that generally does not produce hydrogen is .
3) A drug that can be used to treat iron deficiency anemia is .
(4) In order to prevent certain foods from getting wet, a small bag of desiccant is put in its bag. This desiccant is .
21 (2007 Suzhou City), chemistry is all around us, it is closely related to our lives. Please choose the appropriate letter number to fill in the blanks from the eight substances A. slaked lime, B. soda ash C. natural gas, D. potassium nitrate, E. cellulose, F. vitamins, G. hydrochloric acid, H. sulfuric acid.
(1) The acid contained in human gastric juice is ;
(2) The substance transported by China's West-to-East Gas Pipeline Project is ;
(3) The "alkali" in the Hou's Combined Alkali Method is ;
(4) compound fertilizer applied to farmland is ;
(5) cotton, hemp and other natural plant fibers are the main components ;
(6) can be used to improve acidic soil and can be used to configure the pesticide Bordeaux liquid is .
22 (2007 Changzhou City), (4 points) will be the following terms in the corresponding space (only need to fill in the serial number).
① emulsification ② crystallization ③ deliquescence ④ volatilization
(1) sodium hydroxide solid exposed in the air, the surface becomes wet
(2) open the cork of a reagent bottle containing concentrated hydrochloric acid, the mouth of the bottle appeared white mist
(3) detergent will be washed to remove the grease on the dishes
(4) cooling a hot potassium nitrate saturated solution, the emergence of crystal
. p>23 (2007 Zhenjiang City), (4 points) will be the following names of the operation of the serial number in the back of the line (each serial number only once): ① stirring ② evaporation filtration ④ heating
(1) from saturated brine to get table salt crystals; (2) saturated potassium nitrate solution into an unsaturated solution;
(3) to remove the sediment in the table salt, the first to dissolve, and then ; (4) Concentrated sulfuric acid is injected into water, in order to make the heat quickly distributed .
24 (2005 Changzhou), From the reagents provided, choose one to remove a small amount of impurities (impurities in parentheses) in the following substances. Fill in the serial number of the reagent on the corresponding line (reagents cannot be reused).
For the choice of reagents: ① concentrated sulfuric acid ② water ③ dilute nitric acid ④ hydrochloric acid ⑤ sodium hydroxide solution
(1) Cu powder (Fe) ________ (2) CaCO3 powder (CaCl2) ________ (3) CO (CO2) ________
25 (Nantong, 2007) in our daily life, should be careful to Reasonable intake of nutrients and essential elements.
(1) Protein is a basic substance that forms the basis of life and is an important part of the daily diet. The following foods:
①apples ②raisins ③milk ④rice ⑤soybeans
Among them, the one that is rich in protein is (fill in the number).
(2) The starch ingested by the human body under the catalytic effect of enzymes and water eventually become glucose, glucose in the enzyme catalytic effect of slow oxidation into , at the same time release energy for the body's activities and the need to maintain a constant body temperature.
(3) At present, a kind of health care product called calcium iodate has entered some supermarkets, which contains the essential trace elements are .
26 (2007 Zhenjiang),
Small Li students in the study of knowledge about vitamins, homemade a "Vitamin C" knowledge of a small card, but incomplete, please help him to fill in the table in the space of the content.
"Vitamin C" knowledge mini card
Molecular structure Chemical formula
Relative molecular mass
Properties of Vc Can be soluble in water, and is easily oxidized and destroyed in a heated or alkaline environment
Existence of Vc Green vegetables (e.g., cucumber, lettuce), fruits (e.g., citrus)
Precautions for consuming cucumber
Dos and don'ts of preserving Vc tablets
27 (2007, Suzhou), Try to fill in the blanks with ">" or "<" or "=".
(1) the pH of acid rain the pH of distilled water;
(2) the number of protons in the nucleus and the number of electrons outside the nucleus in a carbon atom;
(3) the metallic activity of sodium the metallic activity of aluminum
(4) the volume fraction of nitrogen in the air the volume fraction of oxygen;
(5) 5g of sodium carbonate powder is added to 95g of solute with a mass fraction of 10% hydrochloric acid, the mass of the solution after sufficient mixing 100g
28 (2007 Xuzhou City), chemistry is closely related to our clothing, food, housing and transportation, please answer the following questions:
(1) clothes on the grease can be decontaminated with laundry detergent is the reason that ____
(2) add iodized water to the rice broth, will appear blue, indicating that the rice broth contains ___
(3) home improvement, the installation of solar shower in the bathroom, it is the solar energy into ___ energy
(4) complex, copper and its alloys in transportation everywhere, now the chromium (Cr) inserted into a solution of Cu (NO3) 2, chromium on the precipitation of red material. Then chromium and copper compared to the metal activity is ____
29 (2007 Xuzhou City), according to the "City Morning News" reported that, in order to improve the water quality of the old Yellow River, May 28 this year, the city's water conservancy department from Weishan Lake to transfer 3 million cubic meters of water into the old Yellow River.
(1) In order to test whether the water quality reaches the standard of ornamental water quality in the scenic area, the acidity and alkalinity of the water can be tested by ____.
(2) In order to protect the excellent water quality of the old Yellow River, please put forward two rationalization suggestions.
①__________________②_____________________.
(3) Aqueous solutions have a wide range of applications in production, life. Adding a small amount of ethylene glycol to the water tank of a car in winter can make the freezing point of the aqueous solution ____ to prevent the water from freezing. The electrolyte in a motor vehicle battery is a solution of sulfuric acid with a solute mass fraction of 28%. If this solution is prepared in the laboratory, the glass instruments to be used are a rubber-tipped burette, ___, ___, and ___.
(4) Water is an important solvent that can dissolve many salts. The color of a salt solution is usually carried by the ions in the solution. It is known that NaCl solution contains Na+ and Cl-, and FeCl3 solution contains Fe3+ and Cl-. It is hypothesized that the reason for the yellow color of FeCl3 solution is related to ____ (fill in the ionic symbols) ions for the reason _________.
30 (2007 Changzhou City), learning chemistry can make us better recognize various phenomena, more reasonable to solve practical problems, and more easily cope with emergencies that may occur in life.
(1) commonly used detergent to wash the oil, because detergent and oil, water will produce a mixture of action; often in the winter in the car tank to add a small amount of ethylene glycol and other compounds can prevent the water in the tank from freezing, because ethylene glycol is dissolved in water to make the solution of the freezing point . (fill in "higher" or "lower")
(2) different iron products taken by the iron protection methods are different. For example, the chain of a bicycle is often protected against rust, and the body of a bicycle is often protected against rust.
(3) The methods of extinguishing fires vary from one fire to another. For example, to put out the fierce fire, the rapid spread of forest fires is usually taken; to put out the fire caused by the aging of electrical wiring should be first, and then extinguish the fire.
Three, simple material inference. This kind of topic highlights the examination of students analytical reasoning ability, logical thinking ability and comprehensive application ability. Teachers can practice so that students master the general solution to the problem and strategy: seize the characteristics of the selected breakthroughs, the use of the method of inference, inverse inference method, the whole method.
31 (2006 Changzhou), the following is a diagram of the relationship between some common substances transformed into each other (some reaction conditions are not specified)
(1) the solid A will be heated sufficiently until no more gas is produced, the filtrate H contains the following substances:
____________________________________________ (write the chemical formula)
(2) Solid B, which has the chemical formula ______________, acts as ____________ in the reaction with colorless liquid E.
(3) If gas Z is the simplest organic substance, its combustion in gas X produces different substances depending on the amount of X and the conditions. Try to write the chemical equation for the reaction of X and Z to form a solid monomer M and a colorless liquid F:
______________________________________________________________.
32 (2006 Nantong), (5 points) industry with marble and hematite as the main raw material
can be produced B and G, the conversion relationship is shown in the figure on the right,
known D, G's main components are monomers.
Try to answer the following questions:
(1) Write the chemical formulas of the two substances industrially produced:
B , G .
(2) Write the chemical equations for the following reactions:
Reaction ②: ;
Reaction ③: ;
Test gas C: .
33 (2007 Suzhou), 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).
Write the chemical formulas of the following substances:
A ; B ; C ; D .
34 (2007 Zhenjiang), it is known that seven substances A ~ G are compounds that appear in junior high school chemistry textbooks, of which F is a commonly used building materials
material; H is a common monomer. The following transformation relationship exists between the substances (the reaction conditions are shown in the figure below).
(1) Write the chemical formula of the substance A .
The solutes in the above blue solution are , .
(2) In ① ~ ⑥ reaction belongs to the synthesis reaction is (fill in the serial number).
(3) In the above transformation process, there are changes that can reflect the great contributions made by the ancient people of China to mankind in chemistry.
Give an example of one of them and express it in a chemical equation.
Four, and the solubility curve of solids related questions. These questions require students to be able to flexibly use the information expressed in the solubility curve, related to the test points are, compare the size of the solubility, compare or calculate the mass fraction of solute in solution, calculate the mass of solution, answer the saturated and unsaturated solutions and many other questions.
35 (2006 Nantong), (11 points) the city near the river and the sea, has a long coastline, marine resources are very rich.
1) seawater sun salt can be obtained crude salt, crude salt in the laboratory after dissolving, , can be made of refined salt.
(2) the brine obtained after solarization contains MgCl2, KCl and MgSO4 and other substances, the right figure is a schematic diagram of their solubility curves.
①Set t1 ℃ when the solubility of MgCl2, KCl and MgSO4 three kinds of substances are a, b, c, then their size relationship is .
②Heat the brine above t2 ℃, according to the solubility curve, the first crystal precipitated is .
36 (2005 Xuzhou City), the solubility curve for us to quantitatively describe the strength of solubility of substances provides a convenient. Please answer the following questions according to the solubility curve on the right:
(1)At 20℃, the solubility of substance A _____ (fill in "greater than", "equal to" or "less than") and that of substance B _____ (fill in "greater than", "equal to" or "less than"). ") the solubility of substance B.
(2) _______ ℃, the solubility of the two substances is equal.
(3) At 60 °C, 80 g of substance A is put into 100 g of water and the mass fraction of solute in the resulting solution is .
37 (2007 Wuxi City), according to the solubility curves of KNO3 and NaCl, answer the following questions:
(1) l0 ℃ when the solubility of KNO3 (fill in "＞", "＜" or "=") solubility of NaCl.
(2) At t °C, mg KNO3 , ng NaCl are dissolved in 20 mL of water exactly saturated, then m____n (fill in ">", "<" or "="). ").
(3) The following process is used in industry to extract refined salt from seawater:
In the above process Ⅰ, Ⅱ, Ⅲ are ① , ② , ③ respectively.
38 Xiao Qiang designed an interesting experiment (shown on the right), and after a long period of time, he observed crystals precipitating out of a small test tube.
(1) The following is part of Xiao Qiang's explanation of this phenomenon, please help him to continue the rest of the explanation to complete: concentrated sulfuric acid is hygroscopic,
.
(2) If the temperature before and after the experiment remains unchanged, the mass fraction of solute in the potassium nitrate solution after the experiment is (greater than, equal to or less than) the mass fraction of solute in the original saturated potassium nitrate solution. The solute mass fraction of the original saturated potassium nitrate solution is greater than (equal to) or less than (equal to).
Calculation of solutions (lesson plan and related exercises)
Learning objectives:
1, through the analysis of the formation of solutions, mastery of the relevant calculations of solutions
2, to develop the ability to analyze the problem of ---- meticulous and rigorous
3, through the practice of the formation of the rigorous, pragmatic scientific attitude
Key points
Troublesome
Integrating knowledge and applying the knowledge of the original saturated potassium nitrate solution, the mass fraction of solute (fill in "greater than" or "less than"), the original saturated potassium nitrate solution. p> Comprehensive use of knowledge, improve the accuracy of analysis
Teaching process:
1, introduction: introduction of the content of the study and the significance of the study
2, review of the basic theoretical knowledge:
Solute mass fraction
saturated solution
solubility of the significance of the solution
3, (guided by the analysis of the) solution of the The calculation of the mass fraction of solute of a solution is the most common of the related calculations. When performing such calculations, there are only two values to consider: the mass of the solute and the mass of the solution.
Problem Analysis 1: Analysis of the Mass of Solute
Theoretical Preparation:
Solute, i.e. the substance that is dissolved. The mass of the solute should then be: ____________________Is it possible to determine the mass relationship between substances based on their composition or constituent relationship?
Students practice "Example 1" and share their experience
Summary: the correct and comprehensive consideration of the problem
Misunderstanding of the "substance put into the water is the solute" caused.
The problem is caused by the incomplete consideration of "whether all the solute is dissolved".
Practice consolidation
Students practiced "Example 2" and practice the exchange of experience
Summarize: the relationship between matter and its composition, composition. The relationship between the mass of a substance and the number of particles
Exercise consolidation
Problem analysis 2: analysis of the mass of a solution
Theoretical preparation:
After completing the analysis of the mass of the solute, the next step is to analyze the mass of the solution. The basic idea is:
(1) solution mass = solute mass + solvent mass
(2) the total mass of the solution = mass of the original solution + the mass of the substance added - the mass of insoluble substances
Students practiced the "Example 3" and practice the exchange of experience
Summarize: solution and its mass change <
Students work on "Example 4" and share practice tips
Summarize: the relationship between mass and volume of a solution
Students work on "Example 5" and share practice tips
Summarize: the effect of a chemical change on a
Summary: Changes in solutions due to chemical changes
Lesson summary: students share their learning experiences.
Attachment: midterm exam questions
I. Multiple choice questions
1, (2007 Zhenjiang) by Mg(OH)2 and MgO composed of a mixture, which was measured to contain magnesium element mass fraction of 48%. Take 10g of the mixture, put it into the appropriate amount of dilute sulfuric acid in just the complete reaction, the mass of solute in the resulting solution ( )
A. 12g B. 24g C. 36g D. 48g
2, (2007 Yancheng) the right graph is the solubility curve of slaked lime. To 20 ℃ saturated clarified lime water (A solution) in a small amount of calcium oxide (CaO) powder, fully reacted. The following statements about the solution after the reaction are wrong
A. The solution must be a saturated solution if the temperature of the solution does not return to 20°C
B. The mass fraction of the solute is greater than that of solution A if the temperature of the solution does not return to 20°C
C. The mass of the solute is smaller than that of solution A when the temperature of the solution returns to 20°C
D. The mass of the solute is smaller than that of solution A when the temperature of the solution returns to 20°C
D. The mass fraction of the solute is smaller than that of solution A if the temperature of the solution returns to 20°C. To 20 ℃, the mass fraction of solute and a solution of equal
3, (2007 Taizhou) is the solubility curve of A, B, C three substances, A, B, C three substances t2 ℃ when the saturated solution is cooled down to t1 ℃, the solution obtained by the correct relationship between the mass fraction of solute
A. A> B> C B. A = B = C
C. A = B > C B＞C D. C＞A＝B
4. (2006 Nantong) It is known that the solubility of potassium chloride is 40 g at t ℃. 25 g of potassium chloride solid is added to 50 g of water at this temperature and fully dissolved, and the mass fraction of solute in the solution formed is
A. 25% B. 28.6% C. 33.3% D. 50%
5. (2006 Suzhou) Take 70 g of a certain temperature. 2006 Suzhou) take 70g of a saturated solution of potassium chloride at a certain temperature, evaporate 10g of water at constant temperature, precipitate 4g of potassium chloride solid, then the remaining solution contains the mass of the solute is
A. 16g B. 20g C. 40g D. 56g
6, (2006 Taizhou) the following substances are exposed to the air for a long time, due to the chemical changes that occur and make the solution mass decreases
A. Concentrated sulfuric acid B. Caustic soda solution C. Concentrated hydrochloric acid D. Lime water
7. (2006 Yancheng) in the preparation of a certain mass fraction of sodium chloride solution, the following operational errors that will cause the solution to reduce the mass fraction of solute
A. Weighing of sodium chloride with a pallet balance, weights on the left plate, but did not use the traveler's code B. Measurement of distilled water by a measuring cylinder to read the water. B. When measuring distilled water with a measuring cylinder, look up at the lowest part of the concave liquid C. When pouring the water in the measuring cylinder into a beaker, water spilled D. When transferring the prepared sodium chloride solution to a fine-mouthed bottle, some of the solution was accidentally spilled
8, (2006) Yancheng electrolysis of water, adding a small amount of sodium hydroxide can enhance the conductivity of water. Now 0.1% of sodium hydroxide solution electrified for a period of time, the following statements are correct A. the solution of hydrogen, oxygen element mass fraction decreased B. the solution of sodium hydroxide mass fraction decreased C. the number of ions in the solution increased D. the solution to reduce the volume of the volume is the volume of the gas produced