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1、初三化学计算题专题复习（Review of chemistry calculation problems）初三化学计算题专题复习(Review of chemistry calculation problems) Special review of calculation questions (raising articles) The relative atomic mass that may be used: Mn-55; Mg-24; Zn-65; Al-27; Ca-40; Cl-35.5; K-39; Cu-64; Fe-56; H-1; O-16; C-12; Na-23; S-3
2、2; N-14; Si-28; Ba-137 First, the average value calculation multiple-choice question: Example 1: a mixture of two metal powders, 30 grams, reacted with sufficient dilute sulfuric acid to produce only 1 grams of hydrogen gas, and the two metals in the mixture may be () A.Mg, Al, B.Zn, Fe, C.Mg, Fe, D
3、.Al, Fe link of the same title 1, an impure iron, one or several metal impurities known it contains copper, calcium and magnesium, generate H20.2g dilute H2SO4 reaction 5.6g such iron with enough time, then, the metal impurities in iron samples must contain is () A. copper, B. magnesium, C. aluminum
4、, D. calcium 2, the magnesium chloride powder containing a certain chloride impurity 95g dissolved in water, after adding sufficient amount of AgNO3 solution, completely react to produce white precipitate 300g, then the impurities in magnesium chloride may be () A.NaCl B.AlCl3 C.KCl D.CaCl2 3, in a
5、sample of 2 kinds of iron may contain Zn, Mg, Al, Cu and other impurities in the metal, 5.6g samples with a sufficient amount of dilute sulfuric acid reaction, 0.20gH2, the iron group metal impurities in samples may not contain (is) A., Cu and Mg, B., Zn and Al, C., Mg and Al, D., Zn, and Cu 4. In a
6、n impure ammonium chloride sample, the mass fraction of nitrogen in the sample is 28% NH4HCO3, II (NH4), 2SO4, NH4NO3, CO (NH2) 2 (); A. only one, B., C., II, D. can not be determined Two, the multiple-choice question H2SO4 solution NaOH solution and 20g20% cases of 2:20g20% after full reaction, dro
7、ps into the purple litmus solution is () A. blue, B. purple, C. red, D. colorless link of the same title 1 of the following substances of the same quality, the highest quality fraction of iron is () A.FeS B.FeCO3 C.Fe2O3 D.Fe3O4 2. In a mixed gas composed of sulfur dioxide and sulfur dioxide, the ma
8、ss ratio of sulfur to oxygen is probably three A., 1, 1, B., 1, 1.25, C., 1, 1.5, D., 1: 2 3. The gas composed of two elements, carbon and oxygen, has been measured. The mass ratio of carbon and oxygen to two elements is 3:5, and the gas is () A. mixture, B., purified compound, C. compound, D. organ
9、ic compound Three, special law type multiple-choice questions Example 3: in a formaldehyde (HCHO) solution, the mass fraction of hydrogen is 10%, and the mass fraction of carbon is correct A.12% B.10% C.8% D.6% link of the same title 1. The mass fraction of sulfur in a mixture of NaHS, MgSO4, and Na
10、HSO3 is 20%, and the mass fraction of oxygen is () A.35% B.25% C.65% D. cannot be calculated 2, the Na, Mg and Al are placed in hydrochloric acid solution, and the hydrogen gas is released at the end of the reaction. The quality is the same A. is the same quality as Na, Mg, and Al The mass ratio of
11、B. to Na, Mg, and Al is 23:12:9 and sufficient hydrochloric acid reaction C. is put into excess amounts of Na, Mg, Al, while hydrochloric acid is of the same mass fraction, same volume and same quality. D. has a mass ratio of 3:2:1 to Na, Mg, and Al Four. Solute mass fraction calculation 1. The solu
12、bility of potassium nitrate at 20 DEG C is known as 31.6g. At this temperature, the 20g potassium nitrate is put into the 50g water to be fully stirred, and the mass fraction of the solute in the solution is about () A.24.0% B.28.6%C.31.6%D.40.0% 2, for a substance 100g solute mass fraction of 10% o
13、f the solution were as follows: the evaporation of 10G water solution 10g, the non crystal precipitation the join solute mass fraction of 10% of the same solute added 10g with solute, and completely dissolved the added 10g water. Four kinds of solution mass fraction of solute from operation after th
14、e order is () A., C., B., D. 3. Sufficient amounts of the following solid substances are mixed with hydrochloric acid with the same mass and the same mass fraction of the solute. If the hydrochloric acid is completely reacted, the minimum mass fraction of solute in the resulting ZnCl2 solution is ()
15、 A.Zn B.ZnO C.Zn (OH) 2 D.ZnCO3 Five, image analysis type multiple-choice questions Example 4: a mixture of existing Na2CO3 and NaHCO3, a classmate for the determination of the content of a certain quantity of the sample is dissolved in water, dilute hydrochloric acid was added dropwise and continuo
16、us oscillation, first reaction: Na2CO3 + HCl = NaHCO3 + NaCl, and then the reaction: NaHCO3+ = NaCl + CO2 = HCl + H2O. Known: the CO2 density at this temperature is 1.98g/L, as measured by the CO2 data with the addition of dilute HCl, as shown on the right. (1) when G HCl is added, CO2 is initiated;
17、 V= mL in the figure. (2) please calculate: what is the mass fraction of HCl added in hydrochloric acid? What is the quality of the Na2CO3 and NaHCO3 in the original sample? (percentage accurate to 0.1%; mass accurate to 0.01g) link of the same title 1. When the oxygen is produced by KCl03 in the la
18、boratory, the mass of MnO2 in the mixture can be correctly indicated in the following pictures. The change of the mass fraction a% of T with time is () 2, the same quality of Mg, Fe, Zn, respectively, and the amount of dilute hydrochloric acid reaction, and its reaction speed and the quality of hydr
19、ogen production is correct 3, when sufficient amounts of Fe and Zn are reacted with dilute hydrochloric acid of the same quality, the relationship between the quality of hydrogen (m) and time (T) is correct 4, to a sufficient amount of dilute hydrochloric acid magnesium, The following figure shows e
20、xactly how it changes 5, an extra-curricular interest group students draw four kinds of experimental changes in the operation of the trend picture, which is correct () A B C D A. at certain temperature, a potassium nitrate crystal is added to a potassium nitrate solution which is close to saturation
21、 B. adds excess sodium hydroxide solution to a mixture of sulfuric acid and copper sulfate C. pour excess sodium hydroxide solution into dilute hydrochloric acid D. adds equal amounts of dilute sulfuric acid to equal mass of magnesium and aluminum 6, to slowly drop into 20% sodium hydroxide solution
22、 oscillation mixing solution composed of 40g hydrochloric acid and copper chloride solution in certain quality and quality, and generate with sodium hydroxide solution precipitation as shown in the figure, the judgment is correct () A. eventually produces precipitation with a mass of 9.8g The solute
23、 mass fraction of B.40g HCl is 27.375% The quality of C. precipitation increases gradually with the addition of sodium hydroxide solution D. when the sodium hydroxide solution is 20g, the reaction solution is Sodium Chloride Solution. Precipitation mass /g 02060 NaOH solution, mass /g 7 (Jinan city)
24、, a mixed solution of 100gBaCl2 and HCl in a beaker filled, to which gradually dropping the solute concentration of Na2CO3 solution was 10%, the quality of relationship quality and drops into the mixed solution of Na2CO3 solution is shown in figure: Please answer the questions according to the probl
25、em: (1) in the process of experiment, there are obvious phenomena of gas releasing, which can also be observed . (2) during the experiment, the total mass of the gas is g. (3) when the Na2CO3 solution is dropped to the B point in the graph, what is the solute mass fraction in the unsaturated solutio
26、n obtained by calculation? (the calculation is accurate to 0.1%) 8. Ordinary brass is made of copper and zinc. It is widely used in making plates, pipes and so on. It is also used in casting machinery parts. A sample of 50.00g brass is used to determine the mass fraction of Cu in a sample using an u
27、nknown concentration of dilute hydrochloric acid. The data are shown below. Q: (1) the mass fraction of Cu in brass. (2) the sample completely reflects the quality of the resulting H2. (3) solute mass fraction of dilute hydrochloric acid. Six, experimental data type calculation problem Example 5: a
28、student has carried out three experiments in order to investigate the quality of iron in copper ferroalloy, and the experimental data are as follows: Experiment times project For the first time The second time Third time The quality of the alloy obtained /g Twenty Twenty Forty The quality of the dil
29、ute sulfuric acid added /g One hundred One hundred and twenty Eighty The quality of hydrogen generated /g Zero point four Zero point four Zero point four According to the students experiment, try to answer the following questions: (1) in the three experiment on the last table, When the iron in the a
30、lloy happens exactly, the quality of the dilute sulfuric acid solution is _g. (2) what is the mass fraction of iron in the copper iron alloy? (3) third times the solution for _ (the mass fraction of solute retention to 0.1%). link of the same title 1, a, B, C three students took a sample of limeston
31、e and 50g hydrochloric acid experiment, the results are as follows: Experiment nail B C The quality of the sample was added /g Five Ten Fifteen The quality of the generated CO2 /g One point seven six Three point five two Four point four Ask: the mass fraction of the calcium carbonate in limestone sa
32、mples. The mass fraction of solute in hydrochloric acid. 2, a group of lime plant in order to determine the carbonate limestone samples of calcium in mass fraction, from 4 g to 20 g limestone samples, dilute hydrochloric acid, adding 4 times the sample (sample in addition to calcium carbonate, the c
33、omposition is not reacted with hydrochloric acid, are insoluble in water), after full reaction by filtration finally, dry operation, weighing, the experimental data are listed in the following table: Dosage of dilute hydrochloric acid Join 5 g for the first time Join 5 g second times Join 5 g third
34、times Fourth times 5 g Quality of remaining solids 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 out the calculation process, the result is accurate to 0.1%). 3, (Beijing) artificia
35、l breeding marine products need a lot of sea water, 1kg seawater contains sodium ion quality is about 10.76g, the quality of magnesium ion is about 1.29g, also contains a large number of chloride ions and sulfate ions. According to the calculation, choose two kinds of salt from the following table,
36、and prepare a simplest and cheapest artificial sea water, so that the content of sodium and magnesium in the artificial sea water is basically the same as that of sea water. material Na2SO4 MgCl2 NaCl MgSO4 Price (yuan /500g) Seven Eight Four Twelve (1) the two kinds of salt selected are. (2) calcul
37、ate the cost of preparing salt for 1t artificial sea water (write out the calculation formula). Seven, balance 1, the balance at both ends were placed filled with plenty of dilute hydrochloric acid beaker, the day transferred to balance, to which a beaker of 5.6g into calcium oxide, to another beake
38、r into the amount of magnesium, to make the final balance balance sheet is required to put the quality of magnesium () A.5.61g B.8.00g C.4.2g D.6.11g 2, in the balance of the two plates are placed equal quality beaker, beaker in each 100g9.8% sulfuric acid solution, to the two burning at the same ti
39、me join which group of metal, the reaction at the end of the balance is still balance () A. zinc, iron, each 7g, B., zinc, iron, each 5g, C., zinc, iron, each 4G, D., zinc, iron, each 3G 3, the scale of the two plates were placed for superior weight two beakers were added, the quality of a sufficien
40、t amount of dilute H2SO4, to the left in the cup into the 0.44gCaO, to make the balance to the balance, can to the right beaker add suitable material is () A.100gCaCO3, B.0.48gMg powder, C.0.924gMgCO3, D.0.44gCu, Al alloy 4. Place a beaker on each tray, balance, and two plates, Two have enough quali
41、ty, etc. the beaker filled and the mass fraction of hydrochloric acid, so that both sides maintain balance. At this point, add 11.2gCaO to the beaker on the left. If the sides are to be balanced again, add the quality of CaC03 to the beaker on the right A.11.2g B.17.6g C.20g D.22.4g Eight, comprehen
42、sive analysis multiple-choice questions Example 6: take a certain quality of the mixed gas of CO and CO2, the amount of Ba (OH) 2 solution, after full reaction, filtration, sedimentation and found that generated the mixed gas of equal mass, mixed gas, the number of carbon atoms and oxygen atoms (rat
43、io) A.1:1 B.1:2 C.28:44 D.181:209 link of the same title 1, CO, CO2 in the mixed gas in the mass fraction of elements oxygen is 64%, the 10g mixed gas by copper oxide enough hot after full reaction, the gas into sufficient lime water, can get a white precipitate () A.10, G, B.20g, C.30g, D.40, G 2.
44、In the laboratory, copper is produced from iron filings, copper oxide and dilute sulphuric acid. There are two ways to make copper: (1) Fe, H2, Cu (2), CuO, CuSO4, Cu If the two methods produced the same quality of copper, the following suggestions: the quality of the iron oxide copper II. The consu
45、mption of the same quality of consumption the same quality of the same quality of the sulfuric acid consumption of ferrous sulfate in different generation. Among them, the actual situation is () A., B., II. C., D., II Reference answer First, the average value calculation multiple-choice question: ex
46、ample 1:B same title link 1, A 2, B 3, C, D 4, D Two, an estimation type multiple-choice question 2:A same title link 1, D 2, B 3, A Three, special rule type choice question example 3:B same title link 1, C 2, B C Four, solute mass fraction is calculated 1, A 2, B 3, C Five, image analysis type mult
47、iple-choice questions Example 4: (1) 5444 (2) solution: (1) the quality of 444 mLCO2 is: When generating 0.88gCO2, the quality of consuming HCl is x g NaHCO3+ HCl = +CO2 = NaCl + H2O 36.544 X 0.88g Solution: x = 0.73g (15-5) = 0.73 x 100% = 7.3% (there are many methods, reasonable to) When adding 5g
48、 hydrochloric acid, YG and Na2CO3 were converted into zgNaHCO3. Na2CO3 + HCl + NaCl NaHCO3 flash 10636.584 Y 5g x 7.3% Z Solution: y, =1.06g., Z, =0.84g. The quality of 556mLCO2: 556mL / (1000mL) * 1.98g/L=1.10g When the 556mLCO2 is released, the reaction mass of NaHCO3 is m. Then: NaHCO3+ HCl = +CO2 = NaCl + H2O 8444 M 1. 10g solution is: M = 2.10g Is the quality of NaHCO3 in the original sample: 2.1g0.84g= 1.26g Answer: the mass fraction of HCl in hydro