物質(zhì)的分離與提純

1、物質(zhì)的分離與提純（ Separationand purificationof substances ）The basic operations in the separation and purification ofmaterialsare collectedintoQQbookmarks. Author:admin Click:317 timesThe result is not ideal national top teacher video tutoring high school curriculum far title sea, near approach! High entran

2、ce, high two entrance, high three entranceI. teaching content: basic operations in the separation and purification of substances, neutralization titrationTwo. Key and difficult points:Three. Knowledge analysis:1. the basic operation of separation and purification of substancesOperation nameScope of

3、application and examplesdeviceOperation pointsFiltration (precipitation, washing)Solid (insoluble) liquid separationCases: the removal of salt in sediment(1) fold the folded filter paper, close to the funnel wall, and the water can not be wet until the bubble, the edge of the filterpaper is lower th

4、an the funnel. When the filter is added, the solution surface of the funnel is lower than the edge of the filter paper, that is, a paste two low and three lean".(2) when filtering: the beaker mouth is in contact with theglass bar; the glass rod contacts with the three filter paper; the funnel m

5、outh is close to the glass beaker wall.(3) water, three times higher than the surface precipitation, immersion, purify the precipitation.Evaporation crystallization (recrystallization)Solid liquid separation: evaporation crystallization of salt solution.The use of substances in the same solvent in d

6、ifferent solvents, the solid, a solid (homogeneous) separation. Example: crystallization separation of KNO3 and NaCl.< ProgID= 1262821669 >(1) the evaporatingdish can be heated directly.Fixed the ironhoop.(2) the glass rod constantly agitated by heating to prevent hot liquid spills, find more

7、solid solution when drying the fireevacuation. Steam the solution with waste heat.Distillation fractionationA liquid mixture that separate boiling pointsExample: the fractions are fractionated from petroleum. acetate was distilled from ethanol, acetic acid and concentrated H2SO4 mixture.Ethyl(1) the

8、 distillationflaskis heated with asbestos net,and thethermometer and mercury bulb are placed in the slightly downward position of the branch pipe.(2) when the total horizontal condensation tube to ensure low condensate natural cooling water is dirty, and condensed vapor flows in the opposite.(3) the

9、 flask into porous ceramic with antibumping. Extraction separationSeparate the two miscible liquids. Separate two mutually insoluble liquids.Example: use CCl4 to extract iodine from iodine water, then separate it(1) the solution is injected into a liquid separating funnel, and the total amount of th

10、e solution does not exceed 3 / 4 ofthe volume; as shown, the two hands hold the liquidseparatingfunnel and the inverted liquid funnel and oscillate repeatedly and vigorously.(2) the separatory funnel on the iron hoops, static layered.(3) open the cock to make the lower liquid run out.Gas washingAir

11、separation (impurity gas reacts with reagent): remove HClimpurities in Cl2 gas with saturated salt water and remove C2H2 in CH4 with Br2 water.< ProgID=, 0, 1262821672, > Mixing gas into a washing bottlePay attention to the flow of gas and make progress short. DialysisSeparation of colloidal p

12、articles from solutes in solution.Example: the removal of NaCl from starchcolloidsby dialysis.Will be purified into the colloid membrane, the membrane bag, immersed in distilled water, dialysis time to fully.heatingImpurityreaction.Example: Na2CO3containsNaHCO3impurities.MnO2 mixed with carbon powde

13、r, impurities can be removed byheating.Stir with glass rods to keep the heat evenlysublimationSeparate substances that sublimate easily. Example:purification of iodine and naphthaleneSalting outThe colloid is separated from the mixture. Example: sodium salt is added to the sodium stearate solution,

14、and saturated solution is added to the egg white solutionIon exchangeSeparate the ions from the liquid. Example: softening and hardening2. neutralization titration Titration process:Stance: the left hand controls the piston or small ball, the right hand shakes the conical flask, and the eye looks at

15、 the change in the color of the solution in the conical flask.Drip rate: drop by bit, and when approaching the end, roll one by one.Finish: the last indicator colordrop is just the changes markedly.end of the titration Record reading (halfwhen thea minutewithout fading)Data processing and error anal

16、ysis3. gas generator tightness check (see Figure 1 and Figure 2) Figure 1, figure 2Such as gas experiment device more, also can consider the method of subsection inspection, the principle is the same as above.The purification of substances is the removal of impurities.Itrefersto the experimentaloper

17、ationof removing impuritiesfrom a substance to increase purity. The separation ofsubstances is the experimental process of separating theconstituentsin the mixture.Therefore,separationcan be seenas an extension of purification methods.1. questions:Is the use of chemical reaction to impurities into g

18、as orinsoluble(orvice versa)and removed (removalmethod), or theimpuritiesintothe requiredmaterial(conversion),but shouldpay attentionto not because of adding reagent and introducingnew impurities. That is:Can be summed up as "no increase, no decrease", "easy separation" and "

19、;recovery"".3. purification of solids or solutions:(2) conversion method. Such as: NaHCO3 (Na2CO3), Na2CO3 (NaHCO3), FeCl2 (FeCl3), and FeCl3 (FeCl2)(1) common reagents for the removal of impurities in gases:Removal of HCl in Cl2 gas: adsorption with activated carbon (Cl2 easy liquefaction

20、)Remove acid gas or halogen: use alkali solution.(2) drying of gas adopts desiccantConcentrated sulfuric acid: in addition to non drying H2S (because of sulfuric acid oxidation, H2S reduction), NH3, almost all can be used.Basic desiccantSolid caustic soda: can not dry sour gas.Alkali lime: not dry a

21、cid gas.Neutral or near neutral desiccantSilica gel: almost all available.Anhydrous calcium chloride:almost allexcept NH3and ethanol.5. removal of impurities in the material:If the sodium sulfate solution contains a small amount of sodium carbonate or other volatile weak acid sodium salt impurities,

22、add a proper amount of sulfuric acid can be. Na2CO3H2SO4 = Na2SO4H2OCO2-Such as ZnCl2 (ZnSO4): add a proper amount of BaCl2 solution.ZnSO4BaCl2 = BaSO4 - ZnCl2Na2CO3 (NaHCO3): heating or adding alkali.(4) removal of impurities by oxidation-reduction reactionsReplacement reactions can be used if rela

23、tively active metal salt solutions contain impurities in the salts of inactive metals. For example, FeSO4 (CuSO4): adding iron powder to filtrate the filtrate. FeCuSO4 = FeSO4CuFeCl3 (AlCl3): added excess caustic solution, filtered and precipitated with hydrochloric acid.(6) removal of impurities in

24、 organic matterSuch as benzene mixed with phenol: add NaOH solution, delamination removed.Ethyl acetate mixed with acetic acid: saturated with sodium carbonate solution, delamination removed.6. note:) (the removalof impurities inthe salt water for electrolysisof alkali) should be: Ba2 (2), in the sp

25、ecific experimentprocess, it is also necessary to select the appropriateinstrument and correct operation. For example, when theimpurities are removed in the solution, the precipitateproduced must be removed by filtration.Ifproduce gas,shoulduse the heatingmethod, make itmore thoroughlyand reduce the

26、solubility, the removal of the impurities; if a gaspurification absorption material, the absorbent is a liquid,with gas washing method; absorbent issolid,witha dryingtube.If the impurities are separated by liquid-liquid extraction, a separate liquid funnel is used.Feasibility: if H2S (HCl), do not u

27、se FeS, because FeS is difficult to react with HCl gas;Purity: if CO2 (H2S), can not use concentrated sulfuric acid, because produce SO2;Ordering: Cl2 (HCl, H2O), first through saturated salt water, and then through concentrated sulfuric acid.Impurity removal technique:(1) in an experimental device

28、for producing gas and removing impurities, if there is a copper sulfate solution in the gas washing tank, it must be used to remove hydrogen sulfide gas.(2) to remove a set of impurity ions separately, and only one ion at one time, and the reagent must be excessive, the finalimpurityremoval reagentm

29、ust be acid,and the lastsecond aresoluble carbonates. The advantage of using carbonate is that it deposits more cations and is easy to remove (plus the corresponding acid).(3) CO2gas mixed with SO2or HCl gas, can pass into the NaHCO3 solution, SO2 solution because of sulfurous acid in water,sulfuric

30、 acid and hydrochloric acid can react with NaHCO3 toform CO2, which removed the impurity gas, and increase theamount of main component; similarly, SO2gas mixed with HCl gas can pass into the NaHSO3solution, hydrochloric acid and NaHSO3 reaction of SO2 gas.typical exampleexample 1 how to remove a sma

31、ll amount of CO2 in CO?Analysis: because CO reacts with O2 to produce CO2, some students think that O2 can be passed into the mixture and ignited to remove the CO. The mistake with this idea is that when a flame is used to ignite a mixture of gases, the flame is extinguished by the presence of large

32、 amounts of CO2; CO cannot burn; and O2 impurities are introduced. Therefore, we must not consider the specific circumstances and conditions, and consider the impurity removal methods in isolation. Thecorrectsolutionis:the mixed gas by hot CuO, the reactionis:CuOCO exercises: CaCl2 (NaCl)Ethane is m

33、ixed with ethylene. With the conversion method, H2, yield, but harsh conditions, can not be used to the laboratory; division, pass into the KMnO4 solution or bromine water, can not increase the yield, but simple and feasible.Another example: ethyl acetate mixed with acetic acid.Adding ethanol, conce

34、ntrated sulfuric acid, heating, addingwater, adding NaOHsolution, adding Na2CO3saturated solution, adding HBr, except for conversion method, and the rest of the method is division.2 to precipitate the ions in the solution containing Ba2, Al3, Cu2, Mg2, Ag, one by one, the following reagents and reag

35、ents are in the correct orderB., HCl, DH2SO4, DNa2S, DNaOH, DCO2?C., NaCl, DNa2SO4, DNa2S, DNaOH, DCH3COOH?D., Na2S, DNa2SO4, DNaCl, DNaOH, DHCl?Answer: BAnalysis: the following four points should be considered in this article:(1) the ions are precipitated one by one, and can be analyzed by the foll

36、owing chart method. Only one kind of precipitation is the first place, so it should be HCl before.Ba2Al3Cu2Mg2AgH2SO4-HCl-H2S-Na2S- -CO2-NaOH- D?-(3) the difference between HCl, H2SO4, or NaCl and Na2SO4 isthat the former is acidic, and the latter is neutral. Whenusing Na2S, it will react with Al3 a

37、nd Cu2 to produce precipitation,so it will dissolve under acidic conditions, so as to achieve the purpose of sedimentation one by one;(4) using CO2or ending with CH3COOHis quite different. Because Al3 is converted to CO2, precipitation is obtained by adding CH3COOH and precipitation is not obtained.

38、example 3 a potassium nitrate solution, which mixed with a small amount of potassium bromide and calcium phosphate. IfAgNO3, K2CO3, KOHand dilute HNO3are the mixtures. If the same reagents are the reagents added must be excessive, the solution,.used as reagents, remove not allowed to be reused, and

39、only K is allowed inAnswer: KOH; AgNO3; K2CO3; HNO3Analysis: the main questionis to analyze why KOH is in front,AgNO3 is behind, not AgNO3 is in front, and KOH is behind.The excessive addition of KOH solution, the 12OH- = Ca3 (PO4)2 - 12H2O4, increased production of OH- solution, and Br-.The additio

40、n of excess AgNO3 solution: AgBr- = AgBr -, Ag3PO4- 3Ag =, AgOH- = AgOH - 2AgOH = Ag, Ag2OH2O, remaining in solution.The K2CO3 solution is added in excess of 2Ag.Adding HNO3: (2), adding reagents according to AgNO3, KOH, K2CO3 and HNO3 sequence is:The addition of excess AgNO3 solution: AgBr- = AgBr

41、-, Ca2,residualsolution,the excessiveadditionof KOHsolution,theprecipitation: 3Ca26 - 12H2O4, solution, increase of OH-. Dueto the largenumber of OH- willmakeAg complete precipitation:= AgOH2AgOH= - AgOH-, Ag2OH2O,but itis difficultto happen:3Ag = Ag3PO4 -, which cannot be completely eliminated.4 we

42、igh an unknown quality beaker with a pallet balance. The "down" said to increase the weight of the tray, use the "arrow"from the tray to reduce weight. Please indicate the weighing process at your table with "up" and "down", and the "" "rideron

43、a scale position(ifthe actualqualityof beaker for 36.8g).Weights (grams)FiftyTwentyTwentyTenFiveAvailabilityThe main pointof the examinationis how to increaseor decreaseweights in the tray and how to read the quality of the code onthe ruler. The correct order for adding weights to a tray is"fir

44、st big, then small."". Correctly tour code quality on ascale, tomake clearthe following twopoints: on thescaleofeach grid represents how much quality (such as the 1g betweenthe 10 lattice, each lattice represents g or 0.1g), the riderwhich sideofthe reference reading (generallyin levelinga

45、nd"0" in frontof thecoincidenceprevail).Sincethesubjectisweighing a beaker of 36.8 g, the weights used are 35 g (20g,10g, 5g), and the tour code is 1.8 G.Answer：Down arrowHereDown arrowHereHerecase 5 existing carbonate ores (mainly BaCO3and CaCO3)shall be separated from the ore by BaCO3 an

46、d removed as much as possible from the Ca2.The lower the content of B:Ca2, the better.From A to B:From D to E:Analysis: the clear meaning, understanding the nature of the material, is the key to the answer.Both BaCO3 and CaCO3 can decompose when heated, producing BaO and CaO, and releasing CO2 simul

47、taneously. BaO and CaO react with water to form and respectively. Because it is soluble inwater, slightly soluble in water, and when the temperature rises, the solubility decreases, so the method of filtration can be used to separate and separate,Then, the pure BaCO3precipitatecan be obtainedby intr

48、oducingCO2 into the filtrate containing.Answer：D, e CO2=BaCO3: H2Ocases of 6 to verifya gas mixturecomposed of H2, COand HCl,please design a test from the figure selection of appropriateexperimentaldevice,and answer the followingquestions:(Note:the figure device can not be reused, some devices can n

49、ot choose.)(2) the function of the first device selected is that the second devices selected are.(2) verify the presence of HCl in the mixed gas, the water vapor in the absorption gas, and eliminate the interference of the water on the product of H2 reduction of copper oxide(1) the gas passing throu

50、gh the aqueous solution will contain water vapor.Concentrated sulfuric acid, solid NaOH, quick lime, etc., and verified anhydrous CuSO4 for water.(3) absorption of CO2 is commonNaOHsolution, solid NaOHand so on; verify CO2with clarified lime water.simulation test questionsThe following1. groups:the

51、funnel;the instrument flask;theburette;the separatoryfunnel; the balance; the cylinder;thedropperto thedistillationflask.What is commonly used intheseparation of substances is ()A. 3, B. 6, C. 4 and 2 D. 4 6 82., a student in the experimental report has the following experimental data: first, using

52、tray balance called second, take the amount of 5.26mL hydrochloric acid,11.7g salt; with a widepH test paper, the solution pH value is 3.5, with standard solution. Where the data is reasonable is ()A., B., II. C., D., II3. the following instruments: the beaker; pan evaporation; the surface of the dish; flasks; the crucible; the bottle and cylinder. What can be heated with an alcohol lamp is.A. 4 B. 3 5 II. 4. C. the D. 3 6 7 2.The following 4. reagents: chlorine; the silver nitrate; the concentrated nitric acid; the concentration of ammonia and C.