物质的分离与提纯(Separation and purification of substances)

物质的分离与提纯（Separation and purification of substances）The basic operations in the separation and purification of materials are collected into QQ bookmarks. Author: admin Click: 317 timesThe result is not ideal [national top teacher video tutoring high school curriculum] far title sea, near approach! High entrance, 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 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 filter paper is lower than 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 the glass bar; the glass rod contacts with the three filter paper; the funnel mouth 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 different solvents, the solid, a solid (homogeneous) separation. Example: crystallization separation of KNO3 and NaCl.< ProgID= 1262821669 >(1) the evaporating dish can be heated directly. Fixed the iron hoop.(2) the glass rod constantly agitated by heating to prevent hot liquid spills, find more 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. Ethyl acetate was distilled from ethanol, acetic acid and concentrated H2SO4 mixture.(1) the distillation flask is heated with asbestos net, and the thermometer 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 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 the solution does not exceed 3 / 4 of the volume; as shown, the two hands hold the liquid separatingfunnel 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 separation (impurity gas reacts with reagent): remove HCl impurities 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 particles from solutes in solution. Example: the removal of NaCl from starch colloids by dialysis.Will be purified into the colloid membrane, the membrane bag, immersed in distilled water, dialysis time to fully.heatingImpurity reaction. Example: Na2CO3 contains NaHCO3 impurities. MnO2 mixed with carbon powder, 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, and saturated solution is added to the egg white solutionIon exchangeSeparate the ions from the liquid. Example: softening and hardening2. neutralization titrationTitration process:Stance: the left hand controls the piston or small ball, the right hand shakes the conical flask, and the eye looks at 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 drop is just the end of the titration when the indicator color changes markedly. Record reading (half a minute without fading)Data processing and error analysis3. 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. It refers to the experimental operation of removing impurities from a substance to increase purity. The separation of substances is the experimental process of separating the constituents in the mixture. Therefore, separation can be seen as an extension of purification methods.1. questions:Is the use of chemical reaction to impurities into gas or insoluble (or vice versa) and removed (removal method), or the impurities into the required material (conversion), but should pay attention to not because of adding reagent and introducing new impurities. That is:Can be summed up as "no increase, no decrease", "easy separation" and "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)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 acid gas.Neutral or near neutral desiccantSilica gel: almost all available.Anhydrous calcium chloride: almost all except NH3 and 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, 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 relatively 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 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 removal of impurities in the salt water for electrolysis of alkali) should be: Ba2 (2), in the specific experiment process, it is also necessary to select the appropriate instrument and correct operation. For example, when the impurities are removed in the solution, the precipitate produced must be removed by filtration. If produce gas, should use the heating method, make it more thoroughly and reduce the solubility, the removal of the impurities; if a gas purification absorption material, the absorbent is a liquid, with gas washing method; absorbent is solid, with a drying tube. If the impurities are separated by liquid-liquid extraction, a separate liquid funnel is used.Feasibility: if H2S (HCl), do not use 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 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 final impurity removal reagent must be acid, and the last second aresoluble carbonates. The advantage of using carbonate is that it deposits more cations and is easy to remove (plus the corresponding acid).(3) CO2 gas mixed with SO2 or HCl gas, can pass into the NaHCO3 solution, SO2 solution because of sulfurous acid in water, sulfuric acid and hydrochloric acid can react with NaHCO3 to form CO2, which removed the impurity gas, and increase the amount of main component; similarly, SO2 gas mixed with HCl gas can pass into the NaHSO3 solution, hydrochloric acid and NaHSO3 reaction of SO2 gas.[typical example][example 1] how to remove a small 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 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. The correct solution is: the mixed gas by hot CuO, the reaction is: CuOCO exercises: CaCl2 (NaCl)Ethane is mixed 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, concentrated sulfuric acid, heating, adding water, adding NaOH solution, adding Na2CO3 saturated 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 reagents 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 following chart method. Only one kind of precipitation is the first place, so it should be HCl before.Ba2Al3Cu2 Mg2 AgH2SO4 --HCl -H2S --Na2S - - --CO2----NaOH- D?---(3) the difference between HCl, H2SO4, or NaCl and Na2SO4 is that the former is acidic, and the latter is neutral. When using Na2S, it will react with Al3 and Cu2 to produce precipitation, so it will dissolve under acidic conditions, so as to achieve the purpose of sedimentation one by one;(4) using CO2 or ending with CH3COOH is quite different. Because Al3 is converted to CO2, precipitation is obtained by adding CH3COOH and precipitation is not obtained.[example 3] a potassium nitrate solution, which mixed with a small amount of potassium bromide and calcium phosphate. IfAgNO3, K2CO3, KOH and dilute HNO3 are used as reagents, remove the mixtures. If the same reagents are not allowed to be reused, the reagents added must be excessive, and only K is allowed in the solution,,.Answer: KOH; AgNO3; K2CO3; HNO3Analysis: the main question is 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 addition 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 -, Ca2, residual solution, the excessive addition of KOH solution, the precipitation: 3Ca26 - 12H2O4, solution, increase of OH-. Due to the large number of OH- will make Ag complete precipitation: = AgOH 2AgOH = - AgOH-, Ag2OH2O, but it is difficult to happen: 3Ag = Ag3PO4 -, which cannot be completely eliminated.[4]] weigh 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 "" "rider on a scale position (if the actual quality of beaker for 36.8g).Weights (grams)FiftyTwentyTwentyTenFiveAvailabilityThe main point of the examination is how to increase or decrease weights in the tray and how to read the quality of the code on the ruler. The correct order for adding weights to a tray is "first big, then small."". Correctly tour code quality on a scale, to make clear the following two points: on the scale of each grid represents how much quality (such as the 1g between the 10 lattice, each lattice represents g or 0.1g), the rider which side of the reference reading (generally in leveling and "0" in front of the coincidence prevail). Since the subject is weighing 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 arrowHereHere[case 5] existing carbonate ores (mainly BaCO3 and CaCO3) shall be separated from the ore by BaCO3 and 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 simultaneously. BaO and CaO react with water to form and respectively. Because it is soluble in water, 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 BaCO3 precipitate can be obtained by introducing CO2 into the filtrate containing.Answer：D, e CO2====BaCO3: H2O[cases of 6] to verify a gas mixture composed of H2, CO and HCl, please design a test from the figure selection of appropriate experimental device, and answer the following questions: (Note: the figure device can not be reused, some devices can not 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 through 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 commonNaOH solution, solid NaOH and so on; verify CO2 with clarified lime water.[simulation test questions]The following 1. groups: the funnel; the instrument flask; the burette; the separatory funnel; the balance; the cylinder; the dropper to the distillation flask. What is commonly used in the separation of substances is ()A. 3,B. 6,C. 4 and 2D. 4 6 82., a student in the experimental report has the following experimental data: first, using tray balance called 11.7g salt; second, take the amount of 5.26mL hydrochloric acid, with a wide pH test paper, the solution pH value is3.5, 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. 4B. 3 5 II. 4.C. theD. 3 6 7 2.The following 4. reagents: chlorine; the silver nitrate; the concentrated nitric acid; the concentration of ammonia and C. and alum B. D. and E. F., and (1) the phenolphthalein (a 22 mixed solution, divided into two groups according to.(3) and identified 1 2mL, 3 drops of 3 unknown liquid, then add4 unknown solution 4mL, no obvious phenomenon in the process of experiment.In combination with the above experiments, you can be sure number 1 is No. 2, No. 3 is, and number 4 is.7. [1998 years test questions] under conditions, there are 2 L, 1 L and 1 L powder, C powder, powder three hot reaction tubes. It is assumed that the gas can react sufficiently through each reactor, and whatever the order of the three tubes in question:(1) is it possible that the exhaust gas is a single gas? Fill in "possible" or "impossible". If possible, the gas is.(2) is there a few (or one) of the original gas that cannot exist in the exhaust gas? (fill in "yes" or "no"). If yes, they (or it) are.(3) are there a few (or one) of the original gases that must exist in the exhaust gas? (fill in "yes" or "no"). If yes, they (or it) are.8. in the following groups of substances, the former is the dirt on the inner wall of the container, and the latter is the chosen detergent. What you think can achieve the purpose of washing is ().The scale of D?? D phosphate; II phenolic resin? D? D ethanol; the sulfur? D? D alcohol; the yellow stain caused by iron salt containing? D? D dilute sulfuric acid; after the brown spot? D? D concentrated hydrochloric acid; dark brown oil U the carbonization of coal experiment the tube on the? D? D soda solution; the reagent bottle Jiusheng alum solution? D? D andcaustic soda solution; silver mirror? D? D silver ammonia solution.The 4 5 7 A. B. 4 5 6 8 2 C. 2 4 5 7 D..9. in pure water, was dripped into methyl orange, litmus or phenolphthalein solution, the color is ().A. red, purple, colorless,B., orange, blue, redSolution whose level is exactly at the scale of 5mL. If the solution of all the burette into the beaker, then the solution volume ().A. is greater than 20mL,B. is less than 20mL,C. equals 20mL, andD. equals 5mL11. [1998 years test questions] in the following table, it is necessary to use a reagent Z to test the ion X in the salt solution. At the same time, when the ion Y exists, the test is still capable of distinguishingReagent Z, ion, X ion, YA. B.12., [1997 national entrance examination questions] chemical experiments must pay attention to safety, the following statement is correct (fill in the label)()A. accidentally splash an acid into your eyes. Rinse immediately with water and blink while washingC. if the solution of phenol is concentrated on the skin, it should be washed immediately with alcoholFourteenIn order to purify the following substances (impurities in brackets), the removal reagent (shown) and the separation method are correctA. solution; liquid separationB.,C.,D. solution, washing gas15. [2000 in Zhejiang, Jiangsu and Jilin provinces of science comprehensive ability test] adding iron powder in ferric chloride, copper chloride and hydrochloric acid in the mixture, after the reaction, the remaining solid after being filtered by magnets attract more cations in solution after reaction is ()A.The following 16. existing equipment or supplies: (1) iron (including iron ring, iron clip) (2) the conical flask (3) acid burette and burette (4). (5) a glass rod (6) dropper (7) scales (including weight) (8) (9). A common funnel (10) the following drugs: (11) solution (13) unknown concentration ofhydrochloric acid (14) distilled water (15) sodium carbonate solution, try to answer the following questions:(1) do acid-base titration reagent, yet is _________.(2) preparation of the substance concentration of the solution, the instrument is the lack of _________.(3) the instrument should be used when filtering is _________ (in number).17. [1997 national college entrance examination test specimen X consists of ferrous oxide and copper oxide, taking two samples of equal mass, as shown in the following experiment.(1) please write the ionic equation for all reactions occurring in step 3.(2) if all the solution Y and all Z powder after full reaction, the quality of insoluble W generation is m, then the quality of copper oxide in X for each sample _________. (expressed in M)18. [1996 national college entrance examination, B, C and A D respectively, <9 > and four in solution a, we use another X solution, as shown by the method, can be determined by A and B, determine the C, D, X, the representative what solution.19.. [1998 Shanghai college entrance examination] preparation of electrolyzed saturated salt water from chlor alkali plantComplete the following blanks according to the sketch map:(1) in the electrolysis process, the chemical reaction equation of the electrode is connected with the positive pole of the power supply to the ______. Near the electrode is connected with the power anode, the pH value of the solution _______ (optional: constant, increase or decrease)(2) industrial salt contains impurities. The ion equation refining process reaction for ______, _____.(3) if the higher salt content, you must add the reagent to remove barium, barium reagents can be ______ (a, B, C optional, multiple points)A. B. C.(4) for effectively removing and adding reasonable order reagents to _____ (optional A.B.C, multiple points)A. first, plus barium reagentB. firstC. add barium reagent first, add later(5) the difference in solubility of the desalting process, through ______, cooling, _____ (fill operation name) to remove (6) in diaphragm electrolysis salt water electrolyzer, divided into anode and cathode area, prevent full contact with the product, is only, the corresponding program for the _________chemical.20. [2001 national college entrance examination questions] answer the following questions:[answers to questions]1. C2. A3. A4. A5. B6.; phenolphthalein;7. (1) impossible (2);(2) 0.625m18., A., C., D., X.19. (1)20. (1) distillation(2) take a small test tube, open the liquid separation funnel, release a small amount of lower liquid, add a little water to it, if the layer is oil layer, not divided into water layer.。