I beg you for 10 to high school chemistry calculation questions. You must have an analysis. Thank you.

Do you have an email address? I can’t post it here ///

12. (Xiangfan City) There is currently 20 grams of a mixture of NaNO3 and Na2CO3. In order to remove the Na2CO3 and prepare a NaNO3 solution, classmate Li Hua put a certain amount of the mixture into Prepare 60 grams of solution in water, and then add 50 grams of Ca(NO3)2 solution to it. It reacts completely and generates CaCO3 precipitate. After filtration, 100 grams of solution is obtained. Find the mass fraction of the solute in the solution.

13. The (Taiyuan City) laboratory recently purchased a batch of limestone and gave it to the students to determine the mass fraction of calcium carbonate. Students add 10% dilute hydrochloric acid to a certain amount of sample until bubbles no longer occur, and finally use 60g of dilute hydrochloric acid.

(1) Calculate the mass of calcium carbonate participating in the reaction. (The calculation result is accurate to 0.1)

(2) The students were unable to calculate the mass fraction of calcium carbonate in the sample because ____________________.

14. An experimental team in Shaoguan City (for experimental area) needs to use zinc particles and dilute hydrochloric acid to produce hydrogen, but the laboratory only has 36.5% concentrated hydrochloric acid. Trial calculation:

(1) To prepare 20 g of 36.5% concentrated hydrochloric acid into 7.3% dilute hydrochloric acid, g of water needs to be added.

(2) How many liters of hydrogen can be obtained by reacting the dilute hydrochloric acid prepared in (1) with a sufficient amount of zinc particles? (The density of H2 is 0.09g/L)

( The calculation result should be rounded to one decimal place)

15. (Zigong City) The soda ash used to steam steamed buns at a certain home contains a small amount of sodium chloride. An experimental team wants to measure the sodium carbonate (Na2CO3) content in the soda ash. . Now take 8g of the soda ash sample, add 136.7g of a certain dilute hydrochloric acid solution, and the reaction will be complete, and 2.2g of gas will be generated at the same time. Trial calculation:

(1) The mass of sodium carbonate in the soda ash sample;

(2) The mass of the solute in the sodium chloride solution obtained after the reaction;

(3) The solute mass fraction of the sodium chloride solution obtained after the reaction.

16. (Nanchang City) Qingqing, in order to determine the mass fraction of calcium carbonate in a certain limestone (the impurities do not react with acid), added dilute hydrochloric acid dropwise to 6.0g limestone sample until no bubbles were produced. , 2.2g of carbon dioxide gas is generated. Trial calculation:

(1) What is the mass fraction of calcium carbonate in the limestone sample? (Write down the calculation process, the result is accurate to 0.1%)

(2) If you want to calculate One missing piece of data in the question is the mass of hydrochloric acid solution consumed by the above reaction.

17. Laboratory technician Zhang (Ya'an City) analyzed the hematite (main component ferric oxide) samples purchased by the iron smelting plant. Take 10.0g of sample. After complete reaction, remove 103.0g of dilute hydrochloric acid and obtain 2.5g of filter residue after filtration (assuming that the impurities are neither soluble in acid nor water; do not consider the loss in the experiment). Find (calculate the result to one decimal place):

(1) What is the mass fraction of Fe2 O 3 in the hematite sample?

(2) The mass of the solute in dilute hydrochloric acid What is the score?

18. (Chongqing City) The aqueous solution of hydrogen peroxide is commonly known as hydrogen peroxide. It will slowly decompose during the placement process. The chemical equation is:

2H2O2==2H2O+O2↑. There is an unused bottle of hydrogen peroxide that has been stored for a long time. The product label on the bottle provides the following information:

①The mass fraction of H2O2 is 30%;

②The mass of the solution inside is 1000g;

③ Experimental measurement shows that the mass fraction of H2O2 is only 10%.

(1) If this bottle of hydrogen peroxide is used to prepare 1500g of medical hydrogen peroxide with a mass fraction of H2O2 of 3%, what is the mass of this hydrogen peroxide needed?

(2) Calculate the mass of decomposed hydrogen peroxide in this bottle of hydrogen peroxide. (Calculation results are kept as integers)

19. (Jingzhou City) Magnesium is easily oxidized to magnesium oxide by oxygen in the air.

There is a roll of magnesium tape marked with 120 g on the label, and its mass is 136 g (assuming that no other changes have occurred except that the magnesium is oxidized, and the oxidation is uniform). Calculate the mass of oxidized magnesium in grams?

(2) Weigh 6.8 g of the above-deteriorated magnesium ribbon and add it to a sufficient amount of hydrochloric acid solution to react. How many grams of hydrogen will be produced by the reaction?

20. (Jiangxi Province) Qingqing, in order to determine the mass fraction of calcium carbonate in a certain limestone (the impurities do not react with acid), added dilute hydrochloric acid dropwise to 6.0g limestone sample until no bubbles were generated. , 1.11L of carbon dioxide gas is generated (the density of carbon dioxide gas under this condition is .977g/L). Trial calculation:

(1) The mass of carbon dioxide produced by this reaction is g; (accurate to 0.1g)

(2) What is the mass fraction of calcium carbonate in the limestone sample? (Write down the calculation process, and the result is accurate to 0.1%)

(3) If you want to calculate the mass of the hydrochloric acid solution consumed by the above reaction, the missing data in the question is.

21. Shandong Province (Course Standard Volume A)) Water is a precious resource, and the fundamental measure to prevent water pollution is to eliminate the source of pollution. Industrial wastewater from a chemical plant is known to contain sulfuric acid. The scientific and technical personnel designed a process to neutralize sulfuric acid while discharging to treat the wastewater of the factory. The plan is as follows:

Please explain through calculation: To make the wastewater of the factory meet the discharge requirements, the flow rate of NaOH solution should be How many?

22. (Zhaoqing City) There is a mixture of Na2CO3 and NaHCO3. In order to measure its content, a classmate took a certain amount of the sample and dissolved it in water. He added dilute hydrochloric acid drop by drop and kept shaking. First, something happened. Reaction: Na2CO3 + HCl = NaHCO3 + NaCl, and then reaction: NaHCO3+ HCl = NaCl + CO2↑+ H2O.

Known: The density of CO2 at this temperature is 1.98g/L. The experimentally measured data

The data of CO2 produced and the addition of dilute hydrochloric acid are as shown on the right.

(1) When g hydrochloric acid is added, CO2 begins to be produced;

V= mL in the figure.

(2) Please calculate: ①What is the mass fraction of HCl in the added hydrochloric acid?

②What are the masses of Na2CO3 and NaHCO3 in the original sample?

(Percentage is accurate to 0.1%, mass is accurate to 0.01g)

23. (Jining City) Dongfang Middle School extracurricular activity group is measuring the concentration of a mixture formed by sodium chloride and sodium sulfate. When forming, the following experiment was conducted: 20g of the mixture was completely dissolved in water, the resulting solution was divided into 4 equal parts, and then a certain amount of barium chloride solution with an unknown mass fraction was added to each. The experimental data are shown in the table below:

The first part, the second part, the third part and the fourth part

The mass of the barium chloride solution added (g) 15 20 25 30

The mass of the precipitate obtained by the reaction (g) 1.40 1.86 2.33 2.33

If the relevant chemical reaction is: Na2SO4+BaCl2=BaSO4↓+2NaCl, please calculate:

⑴What is the mass fraction of the unknown barium chloride solution.

⑵What is the mass fraction of sodium sulfate in the original mixture. (Accurate to 0.01)

24. In order to determine the mass fraction of calcium carbonate in a batch of limestone samples, Nanchong City (Curriculum Reform Experimental Zone) Lime Factory took 4 g of limestone samples and divided 20 g of dilute hydrochloric acid into Add the sample 4 times (except for calcium carbonate, the remaining components in the sample neither react with hydrochloric acid nor dissolve in water). After full reaction, filter, dry and other operations are performed, and finally weighed. The experimental data are as follows: < /p>

The amount of dilute hydrochloric acid added is 5 g for the first time, 5 g for the second time, 5 g for the third time, and 5 g for the fourth time.

The mass of the remaining solid is 3 g 2 g l g 1 g

(1) The mass fraction of calcium carbonate in the limestone sample is;

(2) Calculate the solute mass fraction of the dilute hydrochloric acid (write down the calculation process, and the result is accurate to 0.1%).

38. (Changsha City) Sodium peroxide (Na2O2) is commonly used in submarines to absorb carbon dioxide gas exhaled by officers and soldiers, and produce oxygen to supply human breathing. The chemical equation of the reaction is: 2Na2O2+ 2CO2==2Na2CO3+O2↑. How many grams of oxygen can be generated if 975g of the existing sodium peroxide sample with a mass fraction of 80% reacts with a sufficient amount of carbon dioxide?

39. (Fuzhou City) The device on the right can be used to produce hydrogen and measure the volume of the collected gas

. Classmate Maomao put 13g of zinc particles into the Erlenmeyer flask and added 100g of dilute sulfuric acid into the long-neck funnel. The two reacted completely.

(The chemical equation of the reaction is Zn＋H2SO4 ZnSO4+H2↑)

(1) Find the mass fraction of the solute in dilute sulfuric acid.

(2) The device on the right uses the method to collect hydrogen; if you want to collect 300mL of hydrogen, you should use a mL (fill in "10" or "100" or "500") measuring cylinder.

40. (Hainan Province). Scale will form on the inner layer of the kettle after long-term use. Its main components are calcium carbonate and magnesium hydroxide. It can be removed with hydrochloric acid. Now take 2.5g of scale and 20g of hydrochloric acid. (Excess) fully reacted, all scale was dissolved, and the mass of CO2 generated was measured to be 0.88g. Trial calculation:

(1) Mass fraction of calcium carbonate in scale;

(2 ) The mass of the solution obtained after the reaction.

41. (Shijiazhuang City) Brine is the residual liquid after extracting salt from seawater. It contains a variety of ingredients and has important applications in food, chemical industry, etc. Figure 22 is a column chart of the contents of each component in bitter brine in a salt farm in my country. The salt farm uses bitter brine and shells as raw materials to produce light magnesium oxide according to the process shown in Figure 23. Assuming there is no loss of magnesium during the production process, please calculate the mass of magnesium oxide that can be produced from 1000g of bittern.

42. (Henan Province) Brass is an alloy of copper and zinc. Add 154.7g of dilute sulfuric acid to a certain mass of brass sample, and it will react completely to produce 0.2g of hydrogen.

(1) Calculate the mass fraction of the solute in the solution obtained after the reaction.

(2) To calculate the mass fraction of solute in the solution after the reaction, it is necessary to first find the mass of certain substances. In addition, you can also calculate the mass of ______________ and the mass fraction of ____________ (no specific calculation is required)

43. (Henan Province Experimental Area) Take 12g of limestone (the main component is CaCO3, impurities do not participate in the reaction) is put into a beaker, and 100g of dilute hydrochloric acid of a certain mass fraction is added to it, and the two react completely. After the reaction is completed, weigh the total mass of the remaining material in the beaker to 107.6g (excluding the mass of the beaker, and gas dissolution is ignored). What is the mass of calcium carbonate participating in the reaction? What is the mass fraction of solute in dilute hydrochloric acid?

44. (Yichang City) A chemistry team wanted to determine the mass fraction of basic copper carbonate [Cu2(OH)2CO3] in a copper mine. Weigh 30g of the copper ore sample into a beaker, add 10% dilute hydrochloric acid drop by drop until the reaction is complete, and finally use 146g of dilute hydrochloric acid. (Assuming that the impurities in the copper ore do not react with dilute hydrochloric acid and are not soluble in water) Try to find:

⑴ What is the mass of HCl in dilute hydrochloric acid in grams?

⑵ What is the mass of basic copper carbonate in copper ore in grams? What is its mass fraction?

⑶ What is the mass fraction of the solute in the copper chloride solution obtained after the reaction?

(The chemical equation of the reaction is: Cu2(OH)2CO3+4HCl == 2CuCl2 + CO2↑ +3H2O.

The relative molecular mass of each substance in the reaction: Cu2(OH) 2CO3～222 HCl～36.5 CuCl2～135

CO2～44 H2O～18)

45. (Lanzhou City B) There is a saying in the Qinghai Lake area of ??my country that fishing for alkali in winter is Sun salt in summer. The alkali here refers to Na2CO3, and the salt refers to NaCl. The alkali that people fish from salt lakes will contain a small amount of NaCl.

A research study group weighed 25.0g of solid Na2CO3 containing NaCl, prepared it into a solution, and then added a sufficient amount of dilute hydrochloric acid with a solute mass fraction of 7.3% drop by drop to completely release the gas, and finally collected it to 8.8g carbon dioxide gas.

Try to calculate: ⑴The mass fraction of Na2CO3 in the original solid;

⑵The total mass of hydrochloric acid consumed in the reaction.

46. (Liuzhou City, Beihai City) Take 117g of 10% sodium chloride solution for electrolysis. The chemical equation of the reaction is:

2NaCl+2H2O==Cl2↑+H2 ↑+2NaOH

The relationship between the mass of generated chlorine gas and time is shown in the figure on the right.

Please calculate:

⑴ How many grams of sodium chloride are needed to prepare 117g of 10% sodium chloride solution?

How many milliliters of water? (The density of water is 1.0g·cm-3)

⑵ When sodium chloride reacts completely, how many grams of hydrogen will be generated?

47. (Shaanxi Province) Dilute hydrochloric acid is dropped into a beaker containing 10g of sodium hydroxide solution (with 2 drops of phenolphthalein test solution). When the reaction is complete, the mass of the diluted hydrochloric acid consumed is 5g. Answer and calculate:

(1) The phenomenon of exactly complete reaction is.

(2) Find the mass of the solute in this NaOH solution.

(3) Find the mass fraction of the solute in the resulting solution (the mass of the phenolphthalein test solution is not included).

48. (Shanghai City) A student used a 250mL gas collecting bottle to collect 4 bottles of oxygen and conduct combustion experiments on sulfur, red phosphorus, charcoal, and iron wire.

(1) In order to obtain dry oxygen, the oxygen can be passed through the gas scrubber bottle on the right. Then the liquid contained in the gas cleaning bottle

is_____________.

(2) Write down the experimental phenomenon of iron wire burning in oxygen:

____________________________________________

(3) Write down the chemical equation of red phosphorus burning in oxygen ：

____________________________________________

(4) To prepare the 4 bottles of oxygen ( ) required for this experiment, how many grams of potassium chlorate are needed at least? (Accurate to 0.01g)

49. (Weifang City) Weifang City is rich in limestone mineral resources. Limestone samples from one mine contained only silica impurities (silica is neither soluble in water nor reacts with hydrochloric acid). In order to determine the mass fraction of calcium carbonate in limestone samples, a chemistry extracurricular activity group took 15g of the crushed sample and put it into an Erlenmeyer flask, then added enough dilute hydrochloric acid until no more bubbles were produced, and finally collected the gas. The mass is 5.5g. Try to answer: ⑴The advantages of using crushed ore samples and using massive ore samples to react with hydrochloric acid respectively are:

⑵ Calculate the mass fraction of calcium carbonate in the sample. (Round the result to one decimal place)

50. (Weifang City additional question) It is known that Na2O2 is a light yellow powder that reacts easily with water to produce sodium hydroxide and a kind of wood that can make Mars with Mars. Reignited gas. 1.09g of the existing mixture of Na2O and Na2O2 is reacted with sufficient water to obtain 300g of solution, which contains 1.2g of solute. ⑴Write the chemical equation of the reaction between Na2O2 and water. ⑵ Add hydrochloric acid with a mass fraction of 3.65% to the above solution. If the solution is medium-green after full reaction, what is the mass of hydrochloric acid added? ⑶ Calculate the mass of Na2O and Na2O2 in the original mixture.

Answers to the test questions

1. 800g

9. (1) 9.4%

(2) Protein: 3.1g <18g , the mass of the unqualified nitrogen element is 2.9 grams>0.5 grams unqualified

10. ⑴169 ⑵42.5

11. Solution: Suppose the alloy reacts with hydrochloric acid, the mass of Fe consumed is x, the mass of FeSO4 generated is y

Fe＋H2SO4=FeSO4+H2↑

56 152 2

x y 0.3g

x = 8.4g

y = 22.8g

(1) Carbon mass in the alloy = 8.5g-8.4g=0.1g

c% = ≈1.2% Less than 2%, so the alloy is steel

(2) The mass fraction of the solute in the solution after the reaction =

Answer: (1) The alloy is steel

< p> (2) The mass fraction of solute in the solution obtained after the reaction is 22.8%.

12. (26.4%)

13. (1) 8.2g

(2) The mass of the limestone sample was not measured.

14. (1) 80 g

(2) Solution: Let the mass of hydrogen gas produced by the reaction be X

Zn + 2HCl = ZnCl2 + H2↑ < /p>

73 2

100g×7.3% X

73 : 2 = 100g×7.3% : X

X = 0.2 g

p>

The volume of hydrogen = 0.2 g ÷ 0.09 g/L = 2.2 L

Answer: The volume of hydrogen generated is 2.2 L.

15. Solution:

(1) Suppose the mass of sodium carbonate in the original mixture is x, and the mass of NaCl generated is y

Na2CO3+ 2HCl== 2NaCl+H2O+CO2↑

106 117 44

X y 2.2g

X=106×2.2g÷44=5.3g

< p>Y=117×2.2g÷44=5.85g

(2) The total mass of sodium chloride in the obtained sodium chloride solution is: 5.85g＋(8g-5.3g)=8.55g

p>

(3) The mass of sodium chloride solution is: 8g+136.7g-2.2g=142.5g

The mass fraction of the solute is: 8.55g/142.5g×100%=6%

p>

Answer: Omitted.

16. (1) (2) The solute mass fraction of dilute hydrochloric acid (other reasonable answers are also available)

(1) Solution: Suppose the mass of CaCO3 in 6.0g limestone sample is x

CaCO3+2HCl==CaCl2+H2O+ CO2↑

100 44

x 2.2g

x=5.0g

p>

(2) The solute mass fraction of dilute hydrochloric acid (other reasonable answers are also available)

17. Solution: (1) According to the law of mass conservation: 10.0g—2.5g=7.5g < /p>

(2) The mass fraction of solute in hydrochloric acid is x

Fe2O3 + 6HCl=2FeCl3+3H2O

160 219

7.5g 103.0 gx

160:219 = 7.5g:103.0gx

x=10.0%

Answer: The mass fraction of Fe2O3 in the hematite sample is 75%; The mass fraction of solute in dilute hydrochloric acid is 10%.

18. (1)450g; (2)210g

19. 24g 0.4g

20. (1)2.2

(2) Solution: Assume the mass of CaCO3 in the 6.0g limestone sample is x

CaCO3+2HCl==CaCl2+H2O+ CO2↑

100 44

x 2.2g

x=5.0g

(3) Solute mass fraction of dilute hydrochloric acid (other reasonable answers are also acceptable)

21. Solution: Suppose NaOH solution The flow rate is x.

H2SO4 + 2 NaOH ==== Na2 SO4 + 2H2O (1 point)

98 80

20L／s×1000mL／L×1.04g/ mL×1% The flow rate of the solution is 8.2L/s

22, (1) 0 444

(2) Solution: ① The mass of 44.4 mLCO2 is:

Suppose that When 0.88gCO2 is used, the mass of HCl consumed is x g

NaHCO3+ HCl = NaCl +CO2↑+ H2O

36.5 44

x 0.88g

< p> Solved: x = 0.73g

0.73÷(15-5)×100% = 7.3% (there are many methods, reasonable points will be given equally)

②Suppose adding When 5g hydrochloric acid is used, yg Na2CO3 is converted into zgNaHCO3.

Na2CO3 + HCl ===== NaHCO3 + NaCl

106 36.5 84

y 5g×7.3% z

Solution : y =1.06g. z =0.84g.

The mass of 556mLCO2 is: [556mL ÷(1000mL)] ×1.98g/L=1.10g

Suppose the reaction occurs when 556mLCO2 is released The mass of NaHCO3 is m. Then:

NaHCO3+ HCl = NaCl +CO2↑+ H2O

84 44

m 1.10g Solution: m = 2.10g

Then the mass of NaHCO3 in the original sample is: 2.1g-0.84g= 1.26g

Answer: ①The mass fraction of HCl in hydrochloric acid is 7.3%; ②The original sample contains Na2CO3 1.06g., NaHCO3 1.26 g.

23. 8. Solution: Analyzing the data shows that the reaction between the solution of the third mixture and 25g of barium chloride solution with an unknown mass fraction has exactly completed, and the mass of the barium sulfate precipitate obtained is 2.33g.

Suppose: the mass of barium chloride contained in 25g of unknown mass fraction of barium chloride solution is x, and the mass of sodium sulfate in a mixture of sodium chloride and sodium sulfate is y

Na2SO4 + BaCl2 = BaSO4↓ + 2NaCl

142 208 233

y x 2.33g

x=2.08g

y=1.42g

(1) The mass fraction of barium chloride contained in the barium chloride solution is: =8.32%

(2) The mass fraction of sodium sulfate in the original mixture is: =28.4%

Answer: ⑴The mass fraction of the unknown barium chloride solution is 8.32%.

⑵The mass fraction of sodium sulfate in the original mixture is 28.4%.

24. (1) 75%

(2) Solution: According to the data in the table, after adding 5 g of dilute hydrochloric acid for the third time, 3 g of calcium carbonate and 15 g of dilute hydrochloric acid Just full reaction.

Assume the mass of the solute in dilute hydrochloric acid is x

CaC03 + 2HCl === CaCl2 + H20 + C02 ↑

100 73

3g x

=

x=2.19 g

The solute mass fraction of dilute hydrochloric acid is: ×100%=14.6%

25. 10% 3%

26. (1) 65% (2) 49%

27. 35%

28. 60 22.9kg

p>

29. Solution: The mass of iron oxide contained in 2000t of ore is:

2000t×80%=1600t (1 point)

Suppose 1600t of iron oxide can theoretically The mass of iron produced is x

Fe2O3 + 3CO 2Fe + 3CO2 (1 point)

160 56×2

1600t x

(1 point)

x=1120t (1 point)

The mass of pig iron containing 96% iron is: 1120t÷96%=1166.7t (1 point)

Answer: (omitted)

30. White eating points are generated; 4.4g 8.1%

31, 4.9g

32 , solution, assuming the mass of iron is FeSO4+H2↑

56 98 152 2

X Z Y O.4g

56:2=X:O.4g X=11.2g

152:2=Y: O.4g Y=30.4g

98:2=Z: O.4g Z=19.6g

. (1) Mass fraction of iron powder is: 11.2g∕14 g×100%=80%

⑵The volume of 36% concentrated hydrochloric acid used is:

19.6g÷36%÷1.19g/cm3=45.75 ml

(3) The mass fraction of the solute in the solution obtained after the reaction is:

30.4g÷(11.2g+116.2g-0.4g) ×100%=23.9%

33. 0.53 kg 10.65% 10.65% sodium sulfate solution

34. NaCl MgSO4

The cost of NaCl: 1000kg×10.76g/kg÷(23/58.5)× (4/500) yuan

The cost of MgSO4: 1000kg×1.29g/kg÷(24/120)×(12/500) yuan

35. Solution: Suppose The mass of sodium hydroxide in the solid mixture is x; the mass of sodium sulfate produced by the reaction is y.

2NaOH + H2SO4 = Na2SO4 + 2H2O

80 98 142

x 98g×10% y

80/98=x/ /9.8g x=9.8g×80/98=8g

142/98=y/9.8g y=9.8g×142/98=14.2g

(1) In the original mixture The mass fraction of sodium sulfate:

(2) The mass fraction of the solute in the solution obtained after the reaction:

Answer: Omitted

36. Solution: Assume that in sewage The mass of sodium hydroxide is x

NaOH + HCl == NaCl + H2O

40 36.5

X 18.25g×4%

40x =36.518.25g?4%

The toxic mass fraction of sodium hydroxide in the sewage is:

0.8g25g ×100% = 3.2% Answer: (omitted)

37. Neutralization reaction (metathesis reaction) 5%

38. Solution: Let the mass of oxygen that can be generated be x

The mass of sodium peroxide = 975g × 80 %＝780g

2Na2O2+2CO2==2Na2CO3+O2↑

156 32

780g x

x＝160g

Answer: 160g of oxygen can be generated

39. (1) Solution: Let the mass of solute in dilute sulfuric acid be x

Zn+H2SO4 ZnSO4+H2↑

p>

65 98

13g x

65/98=13g/x

x=98×13g/65＝19.6g

The mass fraction of solute in dilute sulfuric acid = 19.6g 100g×100%=19.6%

Answer: The mass fraction of solute in dilute sulfuric acid is 19.6%.

(2) Drainage; 500

40. Solution: (1) Let the mass of calcium carbonate in scale be x

CaCO3 + 2HCl ==CaCl2 + H2O + CO2↑

100 44

x 0.88g

100∶44=x∶0.88g

x=2g < /p>

The mass fraction of calcium carbonate in scale is 2g/2.5g×100%=80%

(2) The mass of the solution obtained after the reaction is 2.5g+20g-0.88g=21.62g

p>

Answer: The mass fraction of calcium carbonate in scale is 80%, and the mass of the solution after the reaction is 21.62g

41. Solution: Suppose the mass of magnesium oxide that can be produced is x, then: < /p>

142.5g × + 80.0g × = ×x

142.5g × + 80.0g × = ×x

Solution: x= 86.7g

Answer: 86.7g of magnesium oxide can be produced

42. Method 1: (1) Assume the mass of Zn in the alloy is x, and the mass of ZnSO4 generated is y

Zn + H2SO4 = ZnSO4 + H2 ↑

65 161 2

X y 0.2g

65:2=X:0.2g X=6.5g

p>

161: 2=y:0.2g y=16.1g

The mass fraction of the solute in the solution after the reaction is

Answer: The mass fraction of the solute in the solution after the reaction is 10%

(2) Sulfuric acid Sulfuric acid

Method 2: (1) Suppose the mass of H2SO4 participating in the reaction is x, and the mass of ZnSO4 produced is y

Zn + H2SO4 = ZnSO4 + H2 ↑

98 161 2

X y 0.2g

98:2=x:0.2g x=9.8g

p>

161: 2=y:0.2g y=16.1g

The mass fraction of the solute in the solution after the reaction is

Answer: The mass fraction of the solute in the solution after the reaction is 10%

(2) Zinc sulfuric acid

Note: Question (1) of this question uses different solutions, resulting in different answers to question (2)

< p>43

, Solution: The mass of carbon dioxide produced is: 12g+100g – 107.6g = 4.4g

Suppose the mass of calcium carbonate participating in the reaction is x, and the mass of hydrogen chloride in dilute hydrochloric acid is y.

CaCO3 + 2HCl = CaCl2 + H2O + CO2↑

100 73 44

x y 4.4g

Answer: Carbonic acid participating in the reaction Calcium is 10g; the mass fraction of solute in dilute hydrochloric acid is 7.3%.

44. Solution: ⑴The mass of HCl in dilute hydrochloric acid is: 146g×10% = 14.6g

⑵ Assume the mass of basic copper carbonate in the copper ore is x, the generated The mass of copper chloride is y and the mass of carbon dioxide is z.

Cu2(OH)2CO3+4HCl == 2CuCl2 + CO2↑ +3H2O

222 146 270 44

x 14.6g y z

x===22.2g

The purity of basic copper carbonate in copper ore is: ==74%

⑶ y===27g

z= ==4.4g

The mass fraction of the solution obtained after the reaction is: 16.5%

45. The mass fraction of sodium carbonate is 84.8%

The hydrochloric acid consumed in the reaction The total mass is 200g

46. Solution: ⑴The mass of sodium chloride required = 117g × 10% = 11.7g

The volume of water = (117-11.7) g÷1.0g? cm-3 =105.3cm3=105.3ml

(No points will be given if the mass of water is not converted into volume)

⑵ Suppose hydrogen gas xg is generated

Solution 1 : 2NaCl + 2H2O == Cl2↑ + H2↑ +2 NaOH

71 2

7.1g x

71:2=7.1g : x

x=0.2g

Solution 1: 2NaCl + 2H2O == Cl2↑ + H2↑ +2 NaOH

117 2

11.7g x< /p>

117 :2=11.7g: x

x=0.2g

Answer: (omitted)

47. Solution: (1 ) The solution changes from red to colorless.

Suppose the mass of the solute in the sodium hydroxide solution is , and the mass of sodium chloride generated is y

NaOH + HCl ===== NaCl + H2O

40 36.5 58.5

x 5g×7.3% y

x=0.4g y= 0.585g

The mass fraction of the obtained solution is 0.585g/15g ×100 %=3.9%

Answer: The mass of the solute in the sodium hydroxide solution is 0.4 g. The mass fraction of solute in the resulting solution was 3.9%.

48. (1) Concentrated sulfuric acid

(2) Burns violently with sparks shooting out; producing black solid.

(3) 4P + 5O2 2P2O5

(4) Oxygen mass = 4×0.25×1.43 = 1.43 g

2KClO3 2KCl + 3O2↑

2×122.5 3×32

x 1.43

x = 3.65 g

49. Large contact area and fast reaction rate (2 points) 83.3% (5 points)

50. 2Na2O2+2H2O==4NaOH+O2↑(2 points)

30g

The mass of Na2O is 0.31g The mass of Na2O2 is 0.78g