一、常見重點(diǎn)問題答疑I.AnswerstoFrequentlyAskedKeyQuestions1.什么是氫氧化物沉淀法？在鋅冶煉中，用該方法除鐵和從銅溶液中回收銅，分別屬于哪種目的？1.Whatishydroxideprecipitationmethod?Whataretherespectivepurposesofusingthismethodforironremovalandcopperrecoveryfromcoppersolutionsinzincsmelting?解答：Answer:（1）氫氧化物沉淀法是通過往溶液中加堿（如石灰、氫氧化鈉），讓金屬離子和OH?結(jié)合，形成難溶的氫氧化物固體沉淀的方法。(1)Thehydroxideprecipitationmethodisamethodofaddingalkali(suchaslime,sodiumhydroxide)tothesolutiontocombinemetalionsandOH?toformaninsolublehydroxidesolidprecipitation.（2）鋅冶煉中除鐵屬于“去除雜質(zhì)”（把Fe3?變成Fe(OH)?沉淀除去，避免影響鋅產(chǎn)品質(zhì)量）。銅溶液中回收銅屬于“沉淀有價(jià)金屬”（把Cu2?變成Cu(OH)?沉淀，回收銅資源）。(2)Ironremovalinzincsmeltingbelongsto"removingimpurities"(convertingFe3?intoFe(OH)?precipitationtoavoidaffectingthequalityofzincproducts).Recoveryofcopperfromcoppersolutionbelongsto"precipitationofvaluablemetals"(convertingCu2?intoCu(OH)?precipitationtorecovercopperresources).2.在實(shí)際生產(chǎn)中，F(xiàn)e3?通常在pH≈2時(shí)就會沉淀，而Zn2?要在pH≈6時(shí)才沉淀。這說明pH值對氫氧化物沉淀有什么影響？利用這個(gè)特點(diǎn)能實(shí)現(xiàn)什么效果？2.Inactualproduction,Fe3?usuallyprecipitatesatpH≈2,whileZn2?precipitatesatpH≈6.WhatdoesthissayabouttheeffectofpHonhydroxideprecipitation?Whateffectscanbeachievedbyusingthisfeature?解答：Answer:（1）影響：不同金屬離子形成氫氧化物沉淀需要的pH值不一樣，有的在酸性（低pH）條件下就能沉淀，有的要在偏堿性（高pH）條件下才沉淀。(1)Impact:DifferentmetalionsrequiredifferentpHvaluestoformhydroxideprecipitation.Somecanprecipitateunderacidic(lowpH)conditions,whileothersneedtoprecipitateunderalkaline(highpH)conditions.（2）效果：可以通過控制pH值，讓一種金屬離子先沉淀，另一種留在溶液中，比如鋅冶煉中，控制pH≈3，先除去Fe3?，而Zn2?還留在溶液里，實(shí)現(xiàn)鐵和鋅的分離。(2)Effect:BycontrollingthepHvalue,onemetalioncanbeprecipitatedfirst,andtheotheronecanremaininthesolution.Forexample,inzincsmelting,pH≈3iscontrolledtoremoveFe3?first,whileZn2?remainsinthesolution,toachievetheseparationofironandzinc.3.氫氧化物沉淀法在工廠里常用，比如“鋅浸出液除鐵”、“從廢水中回收鎳”。請分別說明這兩個(gè)場景中，控制pH值的主要目的是什么？3.Hydroxideprecipitationmethodsarecommonlyusedinfactories,suchas"ironremovalfromzincleachate"and"nickelrecoveryfromwastewater".PleaseexplainwhatisthemainpurposeofcontrollingpHvalueinthesetwoscenarios?解答：Answer:（1）鋅浸出液除鐵：控制pH值讓Fe3?形成Fe(OH)?沉淀，目的是把鐵雜質(zhì)去掉，保證后續(xù)生產(chǎn)的鋅溶液干凈。(1)Ironremovalfromzincleachate:ThepHvalueiscontrolledtoallowFe3?toformFe(OH)?precipitate.Thepurposeistoremoveironimpuritiesandensurecleanzincsolutionproducedsubsequently.（2）廢水中回收鎳：控制pH值讓Ni2?形成Ni(OH)?沉淀，目的是把廢水中的鎳收集起來，變廢為寶，提高資源利用率。(2)Recoveryofnickelfromwastewater:ThepHvalueiscontrolledtoallowNi2?toformNi(OH)?precipitation.Thepurposeistocollectnickelinwastewater,changewastematerialintothingsofvalue,andimproveresourceutilization.二、常見難點(diǎn)問題答疑II.AnswerstoFrequentlyAskedDifficultQuestions1.某溶液中既有Fe3?又有Cu2?，往里面慢慢加堿調(diào)節(jié)pH值，哪種離子會先沉淀？為什么？（提示：Fe(OH)?比Cu(OH)?更難溶解）1.TherearebothFe3?andCu2?inacertainsolution.WhichionwillprecipitatefirstwhenalkaliisslowlyaddedtoadjustthepHvalue?Why?(Note:Fe(OH)?ismoredifficulttodissolvethanCu(OH)?)解答：Fe3?會先沉淀。因?yàn)镕e(OH)?更難溶解，在較低的pH值下就能形成沉淀；而Cu(OH)?需要更高的pH值才會沉淀，所以Fe3?先析出。Answer:Fe3?willprecipitatefirst.BecauseFe(OH)?ismoredifficulttodissolve,precipitatescanformatlowerpHvalues;Cu(OH)?requiresahigherpHvaluetoprecipitate,soFe3?precipitatesfirst.2.在鋅的沉淀過程中，有時(shí)會出現(xiàn)“堿式鹽”（如ZnSO??Zn(OH)?），而不是純的Zn(OH)?。和純氫氧化物相比，堿式鹽的形成通常需要的pH值更高還是更低？生產(chǎn)中遇到這種情況，說明溶液里可能含有哪種常見離子？2.Duringtheprecipitationprocessofzinc,"basicsalts"(suchasZnSO??Zn(OH)?)sometimesappearinsteadofpureZn(OH)?.DobasicsaltsusuallyrequirehigherorlowerpHvaluestoformthanpurehydroxides?Whichcommonionsmaybecontainedthereinifthissituationisencounteredinproduction?解答：堿式鹽形成需要的pH值更低（比純Zn(OH)?沉淀的pH低）。說明溶液里可能含有硫酸根（SO?2?），因?yàn)閴A式鹽里通常含有硫酸根等酸根離子（如例子中的ZnSO??Zn(OH)?）。Answer:ThepHvaluerequiredforbasicsaltformationislower(lowerthanthepHofpureZn(OH)?precipitation).Itshowsthatthesolutionmaycontainsulfateradicals(SO?2?),becausebasicsaltsusuallycontainacidionssuchassulfateradicals(suchasZnSO??Zn(OH)?intheexample).3.工廠處理含F(xiàn)e2?的溶液時(shí)，常先加H?O?（雙氧水），再調(diào)節(jié)pH除鐵。加雙氧水的目的是什么？這樣做有什么好處？3.WhenfactoriesprocesssolutionscontainingFe2?,theyoftenaddH?O?(hydrogenperoxide)first,andthenadjustthepHtoremoveiron.Whatisthepurposeofaddinghydrogenperoxide?Whatarethebenefitsofdoingso?解答：Answer:（1）目的：把Fe2?變成Fe3?（因?yàn)镕e2?難沉淀，F(xiàn)e3?容易沉淀）。(1)Purpose:TurnFe2?intoFe3?(becauseFe2?isdifficulttoprecipitate,andFe3?iseasytoprecipitate).（2）好處：Fe3?在較低pH值下就能沉淀，不用調(diào)太高pH，避