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已知非零向量,,若•()=0,||=2||,则向量和夹角的余弦值为( )
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高三下学期数学《》真题及答案
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已知向量a和向量b的夹角为135°|a|=2|b|=3则向量a和向量b的数量积a·b=_______
已知二维非零向量X不是二阶方阵A的特征向量.若A2X+AX-6X=0求A的特征值并讨论A可否对角化
已知非零向量abc满足a+b+c=0向量ab的夹角为120°且|b|=2|a|求向量a与c的夹角
已知2维非零向量α不是2阶方阵A的特征向量.若αA满足A2α+Aα-6α=0求A的全部特征值并由此判
已知向量a=21b=xy.1若x∈{-1012}y∈{-101}求向量a∥b的概率.2若x∈[-12
已知非零向量abc满足a+b+c=0向量ab的夹角为120°且|b|=2|a|则向量a与c的夹角为_
已知向量a=21b=xy.1若x∈{-1012}y∈{-101}求向量a∥b的概率2若x∈[-12]
关于平面向量abc有下列三个命题①若a·b=a·c则b=c②若a=1kb=-26a∥b则k=-3③非
已知2维非零向量x不是2阶方阵A的特征向量.1证明xAx线性无关2若A2x+Ax-6x=0求A的特征
已知两个非零向量a与b定义|a×b|=|a||b|sinθ其中θ为a与b的夹角.若a=-34b=02
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-6
8
6
已知两个非零向量a与b定义ab=|a||b|sinθ其中θ为a与b的夹角.若a+b=-36a-b=-
已知向量a和向量b的夹角为30°|a|=2|b|=3则向量a和向量b的数量积ab=_______
已知向量a和向量b的夹角为30°|a|=2|b|=3则向量a和向量b的数量积a·b=.
已知非零向量ab满足向量a+b与向量a-b的夹角为那么下列结论中一定成立的是
|a|=|b|
a=b
a⊥b
a∥b
关于平面向量abc有以下命题:①若a·b=a·c则b=C.②若a=1kb=-26a⊥b则k=.③非零
本小题满分12分已知向量a=21b=xy.1若x∈{-1012}y∈{-101}求向量a∥b的概率2
若两个非零向量满足则向量与的夹角是.
关于平面向量abc有下列三个命题①若a·b=a·c则b=c②若a=1kb=-26a∥b则k=-3③非
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现有含HCl和CuCl2的混合溶液50g向该溶液中逐滴加入溶质质量分数为10%的NaOH溶液生成沉淀的质量与加入NaOH溶液的质量关系如图所示. 1当加入NaOH溶液质量为ag时溶液中的溶质有 2求混合溶液中CuCl2的质量分数. 3求恰好完全反应时消耗NaOH溶液的总质量.
我国民间有端午节挂艾草驱虫辟邪的习俗艾草中含有丰富的黄酮素化学式为C15H10O2有很高的药用价值.下列氧化黄酮素的叙述错误的是
化学与我们的生活密切相关 1田里的水稻叶子发黄并倒下了一片你认为应该向稻田施用的复合肥是.填序号下同 A.CONH22B.KClC.Ca3PO42D.KNO3 2人们误食重金属盐如硫酸铜氯化钡等可通过喝大量豆浆的方法解毒.由此可知喝下列物质中的也可以达到同样的目的. ①牛奶②果汁③蛋清④矿泉水⑤食盐水 3无人驾驶汽车处理系统的核心材料是高纯度的硅.工业制硅的反应之一如下 2X+SiCl4=Si+4HCl.该反应中X的化学式是. 4化学电池在放电时发生化学变化由能转化为能. 5煤燃烧产生的某种气体是形成酸雨的主要原因在煤中加入可以减少其的排放.
有科学家研究发现氧气可通过高能真空紫外线照射二氧化碳直接产生该化学反应模型如图所示关于该反应的说法错误的是
同学们为了制作叶脉书签需要配制400g10%的NaOH溶液. l计算需要称取NaOH的质量g量取水mL. 2将洗净的树叶放在配制好的溶液中煮沸一段时间后取出称量发现溶液的质量减少了200g溶质质量分数也有所减小.然后在剩下的溶液中加入CuSO4溶液直到不再产生沉淀为止向溶液中逐渐加入了16%的CuSO4溶液200克.计算 ①煮沸后剩下溶液中NaOH的质量分数. ②加入CuSO4溶液后刚好完全反应时溶液中溶质的质量分数. 1只需填答案2要求写出计算过程精确到0.1%
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类推是一种重要的学习方法但如果不具体问题具体分析就会产生错误的结论.下列类推结论错误的是 ①CO能与Fe2O3反应生成FeCO也能与CuO反应生成Cu ②NaOH溶液能使无色酚酞试液变红色CuOH2也能使无色酚酞试液变红色 ③有机化合物含碳元素则含碳元素的化合物一定是有机化合物 ④溶液是均一稳定的则均一稳定的液体一定是溶液 ⑤碱溶液呈碱性能使无色酚酞变红则呈碱性的溶液一定是碱溶液.
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TwoofthesaddestwordsintheEnglishlanguageareifonly.Ilivemylifewiththegoalofneverhavingtosaythosewordsbecausetheyconveyregretlostopportunitiesmistakesanddisappointment. MyfatherisfamousinourfamilyforsayingTaketheextraminutetodoitright.Ialwaystrytolivebytheextraminuterule.WhenmychildrenwereyoungandlikelytocauseaccidentsIalwaysthoughtaboutwhatIcoulddotoavoidanifonlymomentwhetheritwassomethingminorlikemovingacupfullofhotcoffeeawayfromtheedgeofacounterorsomethingthatrequiredalittlemoreworksuchastapingpadding衬垫ontothesharpcornersofaglasscoffeetable. Idon'tonlyavoidthoseifonlymomentswhenitcomestosafety.It'sequallyimportanttoavoidifonlyinourpersonalrelationships.WeallknowpeoplewholostalovedoneandregrettedthattheyhadlostanopportunitytosayIloveyouorIforgiveyou.WhenmyfatherannouncedhewasgoingtotheeyedoctoracrossfrommyofficeonGoodFridayItoldhimthatitwasaholidayformycompanyandIwouldn'tbethere.ButthenIthoughtaboutthefactthathe's84yearsoldandIrealizedthatIshouldn'tgiveupanopportunitytoseehim.IcalledhimandtoldhimIhaddecidedtogotoworkonmydayoffafterall. IknowtherewillstillbeoccasionswhenIhavetosayifonlyaboutsomethingbutmylifeisdefinitelybetterbecauseofmypolicyofdoingeverythingpossibletoavoidthateventuality不测的事.AndeventhoughittakesanextraminutetodosomethingrightoritoccasionallytakesanhourortwoinmybusyscheduletomakeapersonalconnectionIknowthatI'mdoingtherightthing.I'mbuyingmyselfpeaceofmindandthat'sthebestkindofinsuranceformyemotionalwell﹣being. 1Whichofthefollowingisanexampleoftheextraminuterule? A.Startthecarthemomenteveryoneisseated. B.Leavetheroomforaminutewiththeironworking. C.Waitforanextraminutesothatthesteaktastesbetter. D.Moveanobjectoutofthewaybeforeitletssomeonefalldown. 2WhydidtheauthordecidetogotoherofficeonGoodFriday? A.Tokeepherappointmentwiththeeyedoctor. B.Tomeetherfatherwhowasalreadyanoldman. C.Tojoinintheholidaycelebrationofthecompany. D.Tofinishherworkbeforethedeadline. 3Whatcanweinferfromthepassage? A.Itisthemostimportantthingtoavoidifonlyinourdailylife. B.Theauthormusthaveagoodrelationshipwithherchildren. C.Weshouldbuyinsurancetomakeourlifebetter. D.Avoidingifonlycanmaketheauthorcomfortable. 4Whatisthebesttitleforthepassage? A.TheEmotionalWell﹣being. B.TheTwoSaddestWords. C.TheMostUsefulRule. D.ThePeaceofMind.
Whileastronautsinspacegettodomanyexcitingthingstheymissoutonordinarythingsthatwealltakeforgranted﹣beingabletowalkonfirmgroundhangingoutwithfamilyanddiggingintoasliceofhotsteamingpizza.Thoughnotmuchcanbedoneaboutthefirsttwothingstheremaysoonbeasolutiontothethirdonethankstothiscool3﹣Dpizzaprinter! AboutayearagoNASAoffered﹩125000toAnjanContractora3﹣Dtechnologyexperttobuildadevicethatwouldallowastronautstomakepizzaondemand.Themechanicalengineerpromisedthathisinventionwouldproducepiesinlargequantitiesthatlookedtastedandevensmelledlikepizzamadeincommonovens. Latelastyeartheengineerpresentedavideoofhisfirstprototype原型thatbeginsbycreatingasinglesliceofdough面团thatiscookedandprintedatthesametime.Thencomesthetomatosauce﹣amixoftomatopowderoilandwaterandfinallyaproteinslicethatresemblescheese.Whilethevideodoesn'tshowthebakingprocesstheinventorsaysthatoncethepizzaisprinteditcanbereadytobeconsumed消耗in7seconds. WhilethepieinthevideolooksdeliciousenoughtoattractanypizzaloverAnjanContractorisfarfromreadyforastronauts.That'sbecausehestillhastofindasolutiontomakethefoodcontainerintheprinterlastfor30years.Thoughthatmaysoundunrealisticactuallyitisnot.AnjanContractorbelievesthattheonlywaythatispossibleisthatthewaterisremovedfromalltheingredientsandthentheyarereducedtothepowderform.Thisasyoucanimaginewillnotbesoeasy.Butwhiletheprintermaynotbereadyforspaceitcertainlylooksreadyenoughforpeopleonearth.HopefullyNASAandContractorwillconsidersellingittothosenotfortunateenoughtogotoMars! 1Whydoestheauthormentionthethingsthatastronautsinspacecannotdo? A.Toaskusnottotakecommonthingsforgranted. B.Toshowtheyliveadifficultlifethere. C.Toshowtheirlifeisboringinspace. D.Tointroducethetopicofthetext. 2NASAoffered﹩125000toAnjanContractormainlyto. A.createsomenewtypeof3﹣Dprinter B.attractmorecompaniestoworkforNASA C.helpastronautsinspaceenjoyfreshpizzaoneday D.producepizzainlargequantitiestoearngreatprofits 3ThebiggestchallengethatAnjanContractorisfacedwithnowisprobablythat. A.hehasnomoneylefttogoonwithhisresearch B.thepizzadoesn'tseemappetizingtopizzalovers C.hehasnowaytomakepizzathatcanlastforthirtyyears D.hecannotmakethefoodcontainerlastfordecades 4What'sthebesttitleofthepassage? A.NASAistryingitsbesttohelpastronautseatbetter B.Astronautsmaysoonbeabletoenjoysteaminghotpizza C.NASAisworkingonmakingpizzaforcommonpeople D.A3﹣Dpizzaprinterhasbeenusedtomakepizza
Themoonhadgonebehindacloudandthereweren'tmanystarsinthesky.AsItookaglance一瞥atmyneighbor'shouseIsawaflame火焰inhis1.IthoughthewashavingamidnightfastfoodsoIwentbacktomy2. Soontherewasa3smellintheairandIguessedsomethingwaswrong.4Ijumpedoutofbedandwentdownstairsto5.Isawfirecomingoutofmyneighbour'skitchen.RightawayI6Fire!Fire!Buttherewasnoonenearbyto7myshoutsforhelp. I8intomyhousecalledtheFireDepartmentandwentbacktomyneighbour'shouse.Irangthedoorbellhitonthedoorand9myneighbour'snamebuttherewasno10.Imanagedto11thehouseandrescuedacatandarabbit. Itriedtothrowwaterthroughthekitchenwindow12itwasnousethefirewastoostrong.13afireenginearrivedandsoonthefiremenputoutthefire.Theyarrivedjust14asthefirewasgoingto15totheotherroomsinthehouse. Whenmyneighbourcamebackhewas16becausehiskitchenwasburntdownbuthethankedmeforcallingtheFireDepartmentandforsavinghis17.HewantedtogivemesomemoneyinreturnbutIdidnot18it. Weekslatermyneighbourrepairedandrestoredhiskitchen.He19metoseehisnewkitchenandtherehegavemeamedal奖章thathehad20orderedfromafactory.Itmademefeelveryhappy. 1A.sittingroom B.bathroom C.kitchen D.bedroom 2A.chair B.table C.bed D.sofa 3A.big B.hot C.special D.burning 4A.Afterawhile B.Allthetime C.Onceinawhile D.Atonce 5A.examine B.search C.listen D.smell 6A.said B.shouted C.received D.smiled 7A.hear B.listento C.ask D.turnto 8A.walked B.rushed C.jumped D.stepped 9A.calledin B.calledup C.calledout D.calledfor 10A.answer B.light C.sound D.fire 11A.takeout B.takeup C.breakdown D.breakinto 12A.and B.but C.because D.so 13A.Luckily B.Sadly C.Unfortunately D.Suddenly 14A.intime B.ontime C.atatime D.attimes 15A.run B.spread C.flow D.return 16A.glad B.sad C.sick D.angry 17A.children B.parents C.life D.pets 18A.expect B.want C.accept D.get 19A.ordered B.begged C.advised D.invited 20A.mainly B.particularly C.specially D.naturally
IdeastoMakeYourSchoolaGreenCampus Universitiesaredoingeverythingtheycantobecomeagreencampus.Buttherearealsoitemsstudentscandotomakeyourcampusmoreeco﹣friendly. Recycleeverythingespeciallypaper! Thereisalargeamountofpaperacollegestudentgoesthroughpersemester.1Weknowthatthesethingscan'tbeavoidedbutthewayyouhandletheuseofallthepapercanreallyhelpcreateabettergreencampus. Buygreen. 2Papercleaningproductsandwaterareproductsthatcanbepurchased购买asrecycledgoods.They'reslightlymoreexpensivethanthenormalproductsbutit'sworthittomakeagreencampus. Walkandbiketoschool. Mostcampusesespeciallythosethataretryingtobecomeamoreeco﹣friendlycampushaveprettygoodpublictransit.3Walkingorbikingwillhelpmakeyourcampusagreenuniversity. 4 Awaterbottlecanberefilledatanywaterfountainandcaneasilybedrankinclassorwhileridingabike.Thiswillsavetheenvironmentbydecreasingtheamountofplasticwasteonyourcampus. Buyusedclothing. Itisusuallythoughtofassomethingtodotosavemoney.5Recyclingclothesminimizetheuseofresourcestomakeclothingandputsadentintheproblemofworldwidesweatshops. A.Carryawaterbottle. B.Itisalsogoodfortheenvironment! C.Buyrecycledgoodsasmuchaspossible. D.Papermadeofthiskindwoodismuchstronger. E.Ontopofthatalmostalluniversitiesarepedestrian行人friendly. F.Itincludesclassnotestermpapersstudentnewspapersandsoon. G.Universitiescallonallthestudentstolearntorecycleallthewastepaper.
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The10thannualInternationalGoSkateboardingDaywillbeheldonJune212012.SkateboardingDayisallaboutfun!Hereisyourguidetosomeoftheeventsaroundtheworld. LosAngelesCalifornia Over10000skateboardersfromaroundtheworldwillgatherinthestreetsofL.A.TheyhavepartneredwithBoardsforBrosanonprofitorganizationthatcollectsandrestores修复skateboardsforchildrenwhocannotaffordtheirownandhaveaskedskateboardersacrosstheUStodonatetheirusedskateboardproducts.Thecelebrationwilllastmostofthedaytime. ManilaPhilippines TheSkateboardingDaytobeheldinthePhilippineswillbeintheManilaforthesecondtime.Manilaishopingtopromotehealthandskateboardingsports.Theeventbeginsat200pmandendsat600pm.TheskateboardersstartfromLiwasangBonifaciowheretheycanskateinthestreetsofP.BurgosRoxasBoulevardanduptoMalatefountaininRajahSolimanParkwheretheeventendswithaProductTossandBestTrickcontest. SylvanLakeAlbertaCanada IfyouhappentobeinAlbertaCanadaandtheweatherisn'tgreatforoutdoorskatingInclineSkate&BMXParkistheplacetogoskateboarding.Inclineisagreatplacetoskateandadaypassthereisonly﹩8foranadulthalfforthosebelow16.OnGoSkateboardingDaytheywillholdacompetitionwiththefirstprizewinnertakinghome﹩600. NewYorkCityNewYork SteveRodriguezownerandfounderofSBoroSkateboardsholdsthebiggestchapteroftheSkateboardingDayintheworld.TensofthousandsofpeoplewillparticipateandJune21stisnowanofficialNewYorkCityholiday.Theeventstartsat10amandendsat6pm.Therewillbeafreeclinicat10amtonsofprizesfoodanddrinks.Fordetailsofthefulldaypleasecheckouthttp://www.Sboro.com. 1ItcanbelearnedthattheBoardsforBrosaimsto. A.provideskateboardsforpoorchildren B.collectusedskateboardproductstothefestival C.searchforcompetitorsforthefestivaleveryyear D.restoreskateboardsonlyforthecompetitors 2Howmuchwilltheypayifacouplewiththeir14﹣year﹣oldchildskateinIncline? A.Eightdollars. B.Twelvedollars. C.Sixteendollars. D.Twentydollars. 3Wherewilltheeventorcelebrationlasttheshortest? A.InManilaPhilippines. B.InLosAngelesCalifornia. C.InSylvanLakeAlbertaCanada. D.InNewYorkCityNewYork.
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“低碳生活”是指生活中所耗用的能量材料要尽量减少从而减低二氧化碳的排放量.下列做法不符合“低碳生活”理念的是
MaryAnningwasanEnglishfossil化石collectordealerandpaleontologist古生物学家.Herfossil﹣huntinghelpedchangethewaypeoplethoughtabouttheworld. MarywasbornintoapoorfamilyinEnglandonMay211799.ShelivedintheseasidetownofLymeRegisinDorset.Thefamilyhadninechildren.OnlyMaryandherbrotherJosephgrewup.Mary'sfathertookhischildrenalongthebeach.Theypickedupshellsandstonestoselltovisitors.Marydidnotgotoschoolmuch.Herfamilywastoopoor.Andschoolsdidnotteachchildrenaboutfossils.Marycouldreadandwrite.Shetaughtherself.Shelearnedaboutrocksandhowbodiesaremade. In1811whenMaryandJosephwerefossilhuntingJosephsawabonestickingoutoftherock.Maryhadahammertochipawayattherock.Verycarefullysheuncoveredit.Shefoundthefirstcompletefossiloftheichthyosaur鱼龙. SincethenMarybecamecrazyaboutfossilhunting.Shelikedtohuntonthebeachafterastorm.Thewindrainandwavesmadetherockscrumble.Itwaseasytospotfossils.MostdaysMarywentfossilhuntingwithherdogTray. RichfriendshelpedMarybysellingfossilsforher.Theysenthermoney.Scientistswrotelettersandcametoseeher.OnegoodfriendwasWilliamBucklandaprofessoratOxfordUniversity.Maryalsoopenedashoptosellfossilsstonesandshells.Shechattedwithvisitors. MaryAnningdiedin1847.Howevolution进化workswasexplainedbyCharlesDarwinnotlongafterMarydied.Herfossilshadhelpedscientistsunderstandhowthingsbegan. 1WhydidMary'sfathertakehischildrenalongthebeach? A.Toenjoylife. B.Tomakealiving. C.Tolookforfossils. D.Toteachthemaboutfossils. 2WhatcanwelearnaboutMary? A.Herfatherwasapaleontologist. B.Herfathereducatedherathome. C.Shehadninebrothersandsistersinall. D.Shemightbepopularatthattime. 3Whowasthefirstonetocatchsightoftherockcontainingthefirstcompleteichthyosaurfossil? A.CharlesDarwin. B.Mary'sdog. C.Joseph. D.Mary. 4Whatdoestheunderlinedwordcrumbleinthefourthparagraphmeans? A.break B.shake C.float D.dive
某工厂的工业废水中含有大量的FeSO4以及一定量的CuSO4和Na2SO4为减少污染并变废为宝某学习小组设计以下流程拟从该废水中回收硫酸亚铁金属铜并利用氨碱法原理“制碱”.除标注外所加药品或试剂均过量部分产物及反应条件略去 回答下列问题 1由步骤①可知FeCu的活泼性由强到弱的顺序是. 2若向步骤②所得的滤液中滴加1~2滴紫色石蕊试液溶液是. 3步骤⑤中加Na2CO3溶液的作用是.由NaHCO3转化成纯碱的化学反应方程式为. 4“NaCl+CO2+NH3+H2O=NaHCO3+NH4Cl”是氨碱法制纯碱中的重要反应.下列叙述正确的是. A.析出晶体后剩余溶液中只有一种溶质 B.该条件下NaHCO3的溶解度比NH4Cl的大 C.析出晶体后的溶液为NaHCO3的不饱和溶液 D.在加压条件下向饱和氨盐水中通入CO2能加速NaHCO3的生成 5该流程①~⑥中发生了复分解反应的有.填写步骤编号
假定英语课上老师要求同桌之间交换修改作文请你修改你同桌写的以下作文.文中共有10处语言错误每句中最多有两处.每处错误仅涉及一个单词的增加删除或修改. 增加在缺词处加一个漏字符号∧并在其下面写出该加的词. 删除把多余的词用斜线\划掉. 修改在错的词下画一横线并在该词下面写出修改后的词. 注意1.每处错误及其修改均仅限一词 2.只允许修改10处多者从第11处起不计分. It'stimeforustograduate.BeforepartingourclassisgoingtoholdthelastclassmeetingwhichthemewillbethePastGoldenDays.Weplantohaveseveralactivitiestobringaunforgettableendingtoourbeautifuldays.Firstlywewillwatchthephotostakeduringthethreeyearsespecialaboutourschoolevents.Itwillsurelymakeeveryonetorecallthosepreciousmoments.Thenwe'llextendoursinceregratitudetoourteachers.Itisthemwhogivewithoutaskinganythingforreturn.Thencameoneofthemostimportantmomentinourlife﹣﹣abigparty.InawordIhopethelastclassmeetingwillmeaningful.
现有50g溶质质量分数为10%的氢氧化钠溶液加入50g溶质质量分数为10%的硫酸铜溶液充分反应过滤除去沉淀所得溶液中含有离子是
Lastweekinanunusualwayastrangertreatedmewithgenerosity.AtanAsiangrocerystoreonabusyeveningIwasshoppingfortheitemsIneeded1myvoluntaryworkofcookingbreakfastonSaturdayatashelterforthehomelessinSanJose.Iwenttothestore2buytofuandvegetables.AsI3waitinlinetofinishthepurchasetheladynexttomeapproachedmetofindout4IwasgoingtoconsumethebigboxoftofuIwasbuying.EnthusiasticallyIrepliedthatIwasbuyingfoodtocookbreakfastforhomelesspeople. WhileIwasgettingreadytopaythebilltomy5amazesheofferedtopayforeverything.Despitemultiplerequestsfor6namesherespondedthatshefeltgoodbecauseIwasdoingthekindofcommunityworkwhichherparentsoncereceivedhelpfrom7theycametothiscountryasrefugees.Henceshewantedtotake8opportunitytoshowhergratitude. Itwasthe9goodrewardIhadeverreceivedformyvoluntarywork10beganthreeyearsago.Inastrangewayweareallconnectedandwefeelgratefulforeachother.
如图是关于氧气的制取与性质实验装置图.回答下列问题 1装置中标有符号a的仪器名称是A装置用于制取氧气写出瓶中发生的化学方程式 2装置D的作用是. 3装置C中硫粉点燃后的现象是产生色火焰.
水是重要资源下列说法正确的是
学习化学最重要的是善于用化学知识去分析解决生产生活中的问题.从化学的角度看下列说法中正确的是
1若核电荷数为16的元素的符号为R则粒子可用离子符号来表示R元素的原子最外层电子数为. 2铁元素是组成人体血红蛋白的重要元素市场上有含少量铁粉的营养麦片在人体胃液中与盐酸反应转化成可吸收的亚铁盐从而达到补铁的目的写出铁粉在胃液中发生的化学方程式铁元素在生成物中的化合价是.
下列实验操作正确的是
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