Tomorrow will be the monthly Chemistry exam for the third grade of junior high school. Write down any questions you have about solutions and acids, alkalis and salts. Extra points. Full marks! There

Tomorrow will be the monthly Chemistry exam for the third grade of junior high school. Write down any questions you have about solutions and acids, alkalis and salts. Extra points. Full marks! There needs to be an answer

Unit 9 Test Paper

1. Multiple-choice questions (only one option for each question fits the meaning of the question.)

1. Among the following chemical instruments, the one that can be used to dissolve solids, prepare solutions, and heat larger amounts of liquids is ( )

A. Gas collecting bottle B. Beaker C． Measuring cylinder D. Test tube

2. Solutions are widely used in our daily lives. The following are solutions ( )

A. Distilled water b. Iodine c. Lime mortar D. Vegetable oil

3. It is known that the solubility of ammonium chloride at 50°C is 50g. In the saturated solution of ammonium chloride at 50°C, the mass of solute: mass of solvent: mass of solution is equal to ( )

A. 1:2:3 B. 2:3:1 C． 3:1:2 D. 1:3:2

4． According to "Shuowen Jiezi" records, our ancestors began to use seawater to dry salt in the Shennong era. The principle of seawater sun salting is ( )

A. Sun and wind evaporate sodium chloride in seawater B. Sun and wind change the solution from saturated to unsaturated

C. Sun and wind cause water to evaporate and crystals to precipitate D. Exposure to the sun and wind reduces the solubility of sodium chloride

5. If you want to drink cool drinks at any time in summer, you can make your own chemical "refrigerator", which means putting a chemical reagent into a certain amount of water to create a small low-temperature environment. This reagent can be one of the following substances ( )

A. Table salt b. Hydrated lime C. sucrose d. Ammonium nitrate

6. Normally, to turn a cup of unsaturated sucrose solution into a saturated solution, the most appropriate method is ( )

A. Add sucrose b. Add water c. Warming up D. Increase pressure

7. Among the following measures to accelerate dissolution, the one that can change the solubility of solids is ( )

A. Grind the solid finely B. Heating c. Stir D. Oscillation

8. When Xiaoxin pulled the tab of the soda can, she heard a "pop" sound and gas rushed out of the soda. Which of the following explanations about this phenomenon is correct ( )

A. The solubility of the gas decreases due to the decrease in pressure B. As the pressure increases, the solubility of the gas becomes smaller

C. The solubility of gases decreases as the temperature increases D. The solubility of gas becomes smaller due to lowering of temperature

9. The picture on the right is the solubility curve of two solid substances A and B. Which of the following statements is correct ( )

A. The solubility of A is greater than the solubility of B

B. At t1℃, in saturated solutions of A and B made with equal amounts of water, the mass of A is greater than that of B

C. At t2°C, the mass fractions of solutes in the two saturated solutions A and B are equal

D. When both saturated solutions A and B are cooled from t3℃ to t2℃, the same amount of crystals will precipitate

10. In the summer, the experimenter prepared a bottle of saturated potassium nitrate solution in the laboratory and sealed it. In the winter, he found that a large number of crystals precipitated at the bottom of the bottle.

This is because ( )

A. The mass of solvent in the solution decreases B. Became an unsaturated solution

C. As the temperature decreases, the solubility of potassium nitrate decreases D. The mass of solute in the solution increases

2. Multiple-choice questions (each question has 1 to 2 options that match the meaning of the question.)

11. If a closed pond is polluted by a large amount of domestic sewage and becomes eutrophic, the change curve of the dissolved oxygen content in the water body is ( )

A. B. C. D.

12. Among the following understandings about solutions, which one is incorrect ( )

A. The solution after the crystals are separated is an unsaturated solution at this temperature

B. Chemical reactions carried out in solutions are usually relatively fast

C. A saturated solution of the same solute must be more concentrated than its unsaturated solution

D. The nutrients in food are digested and turned into solutions, which are easily absorbed by the body

13. At a certain temperature, continuously add sodium chloride solid to a certain amount of unsaturated sodium chloride solution and stir. In this process, the relationship between the mass of sodium chloride added (n) and the mass fraction of solute in the solution (m) is as shown in the figure, the correct one is ( )

A. B. C. D.

14． At 25°C, add a small amount of calcium oxide [known as CaO+H2O===Ca(OH)2] to saturated clear lime water. When the temperature returns to 25°C, which of the following statements about the solution is correct ( ) < /p>

A. The mass of the solute remains unchanged B. Solute mass decreases

C. The mass fraction of solute remains unchanged D. The mass fraction of solute increases

15. As shown in the picture on the right, put two test tubes A and B into a beaker of cold water (both test tubes have undissolved solutes of the solution). If the crystals in test tube A are reduced and the crystals in test tube B are increased, the beaker needs to be The substance added to is ( )

A. Sodium chloride b. Sodium hydroxide C. ice cube d. Ammonium nitrate

3. Fill in the blanks

16. Among the four substances: ① table salt, ② peanut oil, ③ charcoal powder, and ④ sucrose, the one that can form an emulsion when mixed with water is ________ (optional number, the same below). After mixing, this substance and water can be filtered Method separation is _________.

17. Chemistry comes from life, and life contains a lot of chemical knowledge.

(1) The solvent in medical glucose injection is _________.

(2) Using detergent-added water to clean greasy tableware uses the ________(optional "emulsification" or "dissolution") function of the detergent.

(3) Washing clothes with hard water wastes soap and cannot clean the clothes. Over time, the clothes will become hard. _________ methods are commonly used in daily life to reduce the hardness of water.

18. The laboratory needs to prepare 100 grams of potassium nitrate solution with a solute mass fraction of 12%.

(1) Preparing the solution requires completing three steps: calculation, weighing.

(2) What are the options that will result in a smaller solute mass fraction in the resulting solution? (optional letter).

A. There are impurities in potassium nitrate B. Rusty weights were used when weighing

C. The positions of potassium nitrate and weight are reversed during weighing D. A defective weight was used during weighing

E. When measuring water with a measuring cylinder, look up at the reading F. After the preparation is completed, some liquid splashes out when removing it

19. There are many concepts in chemistry that are both opposite and unified. The figure on the right reflects the relationship between saturated solution, unsaturated solution, concentrated solution and dilute solution.

(1) As can be seen from the picture on the right, the relationship between saturated solution, concentrated solution and dilute solution is

_______________________________________________.

(2) 0.9% medical saline can be classified into the _______ area in the picture on the right (optional "Ⅰ", "Ⅱ", "Ⅲ", "Ⅳ"); the current bottle is close to saturation To turn a sodium chloride solution into a saturated solution, the generally used method is _______________________________ or _______________________________.

20． A chemical interest group conducted solution preparation and preliminary purification experiments of coarse salt.

(1) Prepare 200g of sodium hydroxide solution with a mass fraction of 8%:

① Calculation: The required mass of sodium hydroxide solid is grams, and the required volume of water is mL ( The density of water is approximately considered to be 1g/mL).

②Weighing: Adjust the balance of the pallet balance, place a beaker on the plate of the pallet balance, and weigh its mass. Then (fill in the letters in the order of operations) until the balance is balanced.

A. Add sodium hydroxide solid into the beaker B. Add weights and move the weight as needed

The reason why a beaker is used instead of paper to weigh sodium hydroxide in this step is .

③ Use to measure the required water, pour it into the beaker containing the sodium hydroxide solid, stir with to dissolve it, and cool to room temperature.

④Put the prepared solution into the reagent bottle, plug in the rubber stopper and place it in the designated place.

(2) Preliminary purification of coarse salt:

①Weigh 5.0 grams of coarse salt and gradually add it to 10mL of water with a spoon until the coarse salt is no longer dissolved. The sequence of experimental steps that still need to be performed is: weigh the remaining coarse salt, (fill in the number).

A. Filtration b. Calculate yield C. Evaporate D. Weigh refined salt

②The filtering operation is as shown in the picture on the right. Point out the errors:

; ;

;. twenty one. The figure below is the solubility curve of solid substance A.

(1) Point A in the figure represents the ___________ solution of A (optional "saturated" or "unsaturated").

(2) Please fill in the remaining spaces in the table below (choose "get bigger", "get smaller" or "unchange" in columns 1, 2, and 3 of the table).

Project

Process 1 2 3 4

Lower temperature Solvent

Mass Solute

Mass Solute mass fraction Solution state

A→B unchanged point B

B→C unchanged point C

22. In the process of experimental exploration, if there are multiple factors that affect an experimental result at the same time, when we want to explore one of the factors, we must keep the other factors unchanged to explore the impact of this factor on the experimental results.

Complete the experimental investigation: What factors affect the solubility of solid substances in water?

Factor 1: Type of solute

The factor that needs to be changed in the experiment is: the type of solute

The factor that needs to remain unchanged is: temperature

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Operation steps: At room temperature, add 2g each of NaCl, KNO3, and Ca(OH)2 into three test tubes ①, ②, and ③ respectively. Use a measuring cylinder to measure 5 mL of distilled water each, and pour into ① and ② , ③ in three test tubes, and continue (fill in the operating steps) for a period of time to observe the dissolution of each substance.

Experimental phenomenon: There is a small amount of undissolved NaCl in test tube ①, all KNO3 is dissolved in test tube ②, and there is a large amount of undissolved Ca(OH)2 in test tube ③.

Experimental conclusion: When ___________ remains unchanged, the solubility of different types of solid substances in water___________ (fill in "equal" or "unequal").

Factor 2: Temperature (taking KNO3 as an example)

The factor to be changed in the experiment is: ______________

The factor to be kept unchanged is: solute Type (KNO3)

Operation steps: Use a graduated cylinder to measure each 5mL of distilled water, add it to the three test tubes ①, ②, and ③ respectively, then add 5g KNO3 crystals respectively, and keep the test tube ① At normal temperature, heat and maintain test tube ② at 40°C, heat and maintain test tube ③ at 60°C, shake, and observe the dissolution of KNO3 in each test tube.

Experimental phenomenon: There is a large amount of undissolved KNO3 in test tube ①, a small amount of undissolved KNO3 in test tube ②, and all KNO3 is dissolved in test tube ③.

Experimental conclusion: At different temperatures, the solubility of solid matter (KNO3) in water __________ (fill in "equal" or "unequal").

IV. Calculation questions< /p>

23. Solutions are closely related to human life, and the preparation of solutions is a common operation in daily life and chemical experiments. The following table is a comparison table of the density of sulfuric acid solution and ammonia water and the mass fraction of its solute (20°C).

Mass fraction of solute in the solution (%) 4 12 16 24 28

Density of sulfuric acid solution (g/mL) 1.02 1.08 1.11 1.17 1.20

Ammonia water Density (g/mL) 0.98 0.95 0.94 0.91 0.90

Please answer the following questions after careful analysis:

(1) At 20°C, as the mass fraction of the solute in the solution gradually Increase, the density of sulfuric acid solution gradually___________ (fill in "increase", "decrease" or "unchanged"), the density of ammonia water gradually___________ (fill in "increase", "decrease" or "unchange") ).

(2) Take 100g of 12% sulfuric acid solution to prepare a 6% solution. The mass of water added to 100g of 12% sulfuric acid solution should be __________ (fill in "greater than", "less than" or " Equal to ") 100g.

(3) Add 100g water to 100g 24% ammonia water, shake well, the volume of the solution is _______mL (the calculation result is retained to 0.1mL).

24. 100g of a certain sulfuric acid reacts completely with 13g of zinc. Try to calculate: (1) the mass of hydrogen generated; (2) the mass fraction of the solute in the sulfuric acid; (3) the mass fraction of the solute in the solution obtained after the reaction (retained until 0.1%).

V. Additional questions

25. The following table shows the solubility of KNO3 and NaCl at different temperatures:

Temperature (℃) 0 10 20 30 40 50 60 70 80 90 100

KNO3 13.3 20.9 32 45.8 64 85.5 110 138 169 202 246

NaCl 35.7 35.8 36 36.3 36.6 37 37.3 37.8 38.4 39 39.8

(1) When the KNO3 solution contains a small amount of NaCl, it can be purified by ________.

(2) The correct description of the crystals and remaining solution precipitated in (1) is ________ (fill in the number).

A. The remaining solution must be a KNO3 saturated solution B. The remaining solution must be an unsaturated solution of NaCl

C. The above method can completely separate the two D. The precipitated crystals only contain KNO3

(3) At a certain temperature, completely dissolve the mixture containing 69g KNO3 and 18g NaCl in 50g water. If you want to change the temperature to make KNO3 precipitate but NaCl does not precipitate, then the range of temperature T (℃) is ________℃ (the solubility of potassium nitrate and sodium chloride does not affect each other).

26. As shown in the figure, a small plastic ball is placed in saturated salt water at room temperature.

(1) Now add a small amount of salt crystals, stir thoroughly and let it stand. Under the condition that the temperature remains unchanged, what changes will occur in the sinking and floating of the ball on the liquid surface? Briefly describe the reasons: __________________________________________________.

(2) If you want to make the ball float slightly without external force, the specific method you are going to take is:

____________________________________________________________.

Reference answers and scoring standards

1. Multiple-choice questions (if you do not complete the additional questions, each question will be worth 2 points, ***20 points; if you complete the additional questions, each question will be worth 20 points) 1 point, ***10 points)

Question number 1 2 3 4 5 6 7 8 9 10

Answer B B A C D A B A C C

2. Multiple choice questions (each question is worth 2 points, ***10 points.)

Question number 11 12 13 14 15

Answer D AC A BC B< /p>

3. Fill-in-the-blank questions (1 point for each blank, ***36 points.)

16. ② ③

17． Water emulsification boiling

18. (1) Dissolution (2) ACDE

19. (1) The saturated solution may be a concentrated solution or a dilute solution

(2) III Add sodium chloride solid until it no longer dissolves and evaporate the solvent until crystals just precipitate;

20. (1) ①16 184 ②Left BA Sodium hydroxide is easy to deliquesce (or sodium hydroxide is corrosive)

③Graduated cylinder glass rod ④Label

(2) ①ACDB ②Not available Use a glass rod to drain the filter paper above the edge of the funnel

The filter paper is not close to the inner wall of the funnel and the end of the funnel tip is not close to the inner wall of beaker B (the answers are not required in order, just be reasonable)

twenty one. (1) Unsaturated

Item 1 2 3 4

A→B unchanged unchanged saturated

B→C becomes smaller becomes smaller saturated

(2)

22. Oscillation temperatures are not equal Temperatures are not equal

IV. Calculation questions (***14 points.)

23. (1) Increase (1 point) Decrease (1 point) (2) Equal to (2 points) (3) 210.5 (2 points)

24. (1) 0.4g (2 points) (2) 19.6% (3 points) (3) 28.6% (3 points)

5. Additional questions (2 points for each blank, ***10 points). )

25． (1) Cooling crystallization (2) A (3) 20~70

26. (1) The sinking and sinking conditions remain unchanged. Because sodium chloride crystals are put into a saturated solution of sodium chloride, the sodium chloride will not continue to dissolve and the density of the solution will remain unchanged.

(2) Possible answers: ① Crystals such as potassium nitrate (which does not react with sodium chloride) can be added to increase the density of the solution; ② Crystals such as silver nitrate (which does not react with sodium chloride) can be added But it will increase the density of the solution) crystals to increase the density of the solution; ③ You can add sodium chloride crystals after raising the temperature to increase the density of the solution; ④ You can add other substances that are denser than saturated salt water and are miscible with salt water solution.