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工业上侯氏制碱法得到的纯碱产品中常含有少量的氯化钠杂质，化验员要对每批次的纯碱产品进行检验．在实验室中取27g纯碱样品，平均分成五份依次加入到盛有100g稀盐酸的锥形瓶中（锥形瓶的质量为60g），每...
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用侯氏制碱法制得的纯碱中常含有少量的氯化钠为测定某纯碱样品中碳酸钠的质量分数小雯同学称取该样品5.6
纯碱在玻璃洗涤剂等工业上广泛应用著名化学家侯德榜对改进它的生产技术做出杰出贡献运用侯氏制碱法制得的纯
我国制碱工业的先驱﹣﹣侯德榜为纯碱和氮肥工业技术的发展做出了杰出的贡献运用侯氏制碱法制得的纯碱可能
纯碱在玻璃洗涤剂等工业上广泛应用著名化学家侯德榜对改进它的生产技术做出杰出贡献．运用侯氏制碱法制得
我国化工专家侯德榜的侯氏制碱法为世界制碱工业做出了突出的贡献．工业上用侯氏制碱法制得的纯碱中含有一
我国化工专家侯德榜的侯氏制碱法为世界制碱工业做出了突出的贡献工业上用候氏制碱法制得的纯碱中含有一定量
纯碱在玻璃洗涤剂等工业上广泛应用著名化学家侯德榜对改进它的生产技术做出杰出贡献运用侯氏制碱法制得的纯
我国化工专家侯德榜的侯氏制碱法为世界制碱工业做出了突出的贡献.工业上用侯氏制碱法制得的纯碱中含有一定
我国制碱工业的先驱――侯德榜为纯碱和氮肥工业技术的发展做出了杰出的贡献运用侯氏制碱法制得的纯碱可能含
我国化工专家侯德榜的侯氏制碱法为世界制碱工业做出了突出的贡献工业上用侯氏制碱法制得的纯碱中含有一定量
侯德榜是我国著名的化学家由他发明的侯氏制碱法制得的纯碱中可能含有少量氯化钠现取仅含氯化钠杂质的纯碱样
用侯氏制碱法制得的纯碱常含有少量的氯化钠．将10g含有氯化钠的纯碱加入到102.32g稀盐酸中恰好
某同学在实验室用侯氏制碱法原理制得的纯碱常含有少量的氯化钠将5.6g含有氯化钠的纯碱样品溶解于96.
侯德榜是我国著名的化学家由他发明的侯氏制碱法制得的纯碱中可能含有少量氯化钠现取仅含氯化钠杂质的纯碱样
.用侯氏制碱法制得的纯碱常含有少量的氯化钠将10g含有氯化钠的纯碱溶解于102.32g稀盐酸中恰好完
工业上用候氏制碱法制得的纯碱样品中含有一定量的氯化钠现称取只含有氯化钠杂质的纯碱样品23.3g放入盛
我国化工专家侯德榜的侯氏制碱法为世界制碱工业做出了突出的贡献．工业上用侯氏制碱法制得的纯碱中含有一
工业上用侯氏制碱法生产的纯碱Na2CO3中往往含有少量的氯化钠现将12g含有氯化钠的纯碱加入到一定量
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分别写有数字﹣10π的五张大小和质地均相同的卡片从中任意抽取一张抽到无理数的概率是．
函数y＝中自变量x的取值范围是
分式方程的解为x＝．
如图双曲线y＝经过点P21且与直线y＝kx﹣4k＜0有两个不同的交点． 1求m的值． 2求k的取值范围．
假定你是李华你的朋友Peter想了解你校于五月举办的中国传统文化艺术节.请你给Peter写封回信内容包括 1.举办艺术节的目的 2.介绍你最喜欢的一个艺术节活动 3.邀请Peter参加并告之艺术节活动的时间. 注意1.词数100左右 2.可以适当增加细节以使行文连贯.
因式分解ax﹣ay＝．
我国古代的数学名著九章算术中有下列问题“今有女子善织日自倍五日织五尺．问日织几何”其意思为今有一女子很会织布每日加倍增长5日共织布5尺．问每日各织多少布根据此问题中的已知条件可求得该女子第一天织布尺．
计算﹣10﹣2sin30°+﹣1+﹣12019
下列四个图形中不是轴对称图形的是
WHO'SWHOINTHEZOO? IsitamazingthattheWHO'SWHOINTHEZOOmakesitfunforyoungchildrentosave?WiththehelpofStandardBank'sKidzAPPandtheBigFiveanimalfriendsteachingyourchildrenaboutmanagingtheircashhasneverbeenmorefun.LettheWHO'SWHOINTHEZOOshowyourlittleoneswhatitmeanstoearnandsavemoneyaswellasshareintheenjoymentofspendingtheirwell﹣earnedcash. Elephant Asyourchildrenusethemobileapptocompletevariousactions﹣achievingsavingsgoalscompletingmissionsandachievingwishes﹣herevariousmedalswillberewarded. Earnedmedalsaredisplayedintheelephanthabitataswellaslockedmedalsstilltobeachieved. Leopard Rewardyourkidswithpocketmoneyforcompleting‘missions'householdchoresachievementsetc. Youcancreateamissionforyourchildoryourchildcanrequestanewmission.Oncecreateditmustbeaccepted.Themissionneedstobecompletedbyyourchildandapprovedbyyoubeforeyoucanpayhimorher. Lion Helpyourchildrencreateandfulfilwishes.Wishcardsandtheirsavingsprogresscanbetrackedfromyourbankingapp. Oncetheirsavingsgoalisreachedlionwillinformyouoftheirachievement. Buffalo Kidzcanrequesttowithdrawcashorpurchaseairtimeanddatausingtheirsavings. Rhino Rhinoshowsyourchild'slatestaccountbalanceandtransactions. DownloadtheStandardBank'sKidzAPPfromAppleAppStoreonthephone.UsethecommentsectiontointeractwithotherStandardBankcustomersandbankconsultants. 1WhatistheWHO'SWHOINTHEZOOdesignedfor? A.Playersofboardgames. B.Kidsforself﹣servicebanking. C.Parentsforonlinebanking. D.Travelersinthezoo. 2Rewardswillbepaidif. A.thekidsfulfilyourcreatedmissions B.yourkidsgetenoughlockedmedals C.youkeeptheaccountbalanced D.youapprovetherequestviaKidzAPP 3Whichofthefollowinganimalsisrelatedtospending? A.Rhino. B.Leopard. C.Lion. D.Buffalo.
Theboysatonhischairwithhishandabovethekeyboard.Hethoughtaboutwhattowrite. Herecalledthatthecompetitiondeadlinewasmerelyaweekaway.Buthestillhadnotevenstartedonhispiece.Helookedatthebrochureagain.uWRITINGCOMPETITION!thetitleread.Hismomhadencouragedhimtoenterthewritingcompetitionandnowhewastakingitonashispersonaltaskfortheholidays. Astheboyreflectedonhispreviouswritingeffortsherealizedhowhopelesshistaskofwinningwas.Everystoryheeverwrotewasbasedonotherstories.Hehadlittleimaginationandunfortunatelyimaginationwasthekeytowriting. Suddenlyhehadabrainwave.Thistimehecameupwithanoriginalandimaginativestory. Thewordsshottowardshimlikeastormofleaves.Wordswerecomingeasilyflowingthroughhimfasterthanhecouldtype.Hetypedfasterthanheeverhadbefore.Hecontinuedtotypeamazedathoweasywritingthisstorywas.Theboycouldnotstopwriting.Helookedatthewordcountandsawthenumberu248^staringrightbackathim.Hewasnotevenhalfwayyet. Thenheheardthecallofhismothersayingtimeforbed.Hecontinuedwritingthepieceignoringher.Hehadtomakeupforthetimehehadlostthinkingaboutatopictowrite. Finallyhefinished.Thewordcountnowread498. Perfecthethoughtjustunderthewordlimit.Heknewthiswasthestorythatwouldwin. HewentontoGoogleandsearchedforthecompetition.HefoundthepagebuttherewasnoEnterbutton. 1Whatcausedtheboytotakepartinthewritingcompetition? A.Anewcomputer. B.Theprizemoney. C.Hisowninterest. D.Hismom'sadvice. 2Howdidtheboyfinishhisearlierwriting? A.Hismomhelpedhim. B.Hecopiedothers'ideas. C.Hisfriendsassistedhim. D.Heusedhisimagination. 3Whydidtheboydelayhiswriting? A.Becausehewasterriblylazy. B.Becausehedidn'tknowwhattowrite. C.Becausehewasn'tconfident. D.Becausehereadtoomanystories. 4Whichmightbethemaximumwordlimitforeachentry? A.100. B.250. C.500. D.1000.
Thehemlock铁杉treesalongtheWappingerCreekNewYorklookhealthy.HoweverscientistGaryLovettsaysthewhiteballswhichprovideprotectionforthebugsarecreatedbyatinyinsect.It'shardtobelievethetinybugcouldkillatree.Howevertreescanendupwithmillionsandmillionsofthepests.Whentherearethatmanyitendsupkillingthetree. ThebugfromEastAsiaisslowlykillingtreesacrosstheUSA.Thetrouble﹣makingbugisjustoneofmanyinvasive入侵的peststhathaveslippedintotheUnitedStates.Theycanhurtotherlivingthingsintheirnewhome. Manyinvasivepestsarriveonwoodenpalletspiledinsideshippingcontainers.Theysupportandseparategoodsandkeepthemfromslidingaround.Invasivepestsoftentunnelintothepallets.Howcanwestoppestsfromridingonpallets?Lovettsaysnewrulesareneeded.Thecompaniesthatmakepalletsdon'twantmorerules.Congresshasaddedanamendment修正案inthe2018FarmBilltotryandpreventthisproblem.HoweverLovettisnothopefulitwillmakemuchofadifference.Palletsarecheckedbyinspectors.Manyaresprayedwithbug﹣killingpesticide.IbelieveinthesystemsaidBrentMcClendonpresidentofTheNationalWoodenPalletandContainerAssociation.Healsosaidshippingcontainersarecheckedverycarefully. Stilleachyear13millioncontainersareshippedtotheU.S.Eachisfullofwoodenpallets.LovettsaysInspectorscan'tpossiblycheckeverything.Allittakesareafewbadpalletsweshouldgetridofwoodenpallets.Hebelievespalletsshouldbemadeofplasticoreco﹣compositewood.Eco﹣compositewoodisamixofwoodfiberandplastic.Insectscannothideintoit.Oneproblemisthatthesechoicescostmore.Theymaybeworththeextramoneythough.InvasivepestscosttheU.S.﹩5billionayear.Treesdon'tjustdieinforests.Theyalsodieincitiesandouryards.Thentheyneedtobereplaced.Thatcostsmoneytoo. 1AllthestatementsareTRUEexceptthat. A.pesticidehasbeenappliedtobug﹣killing B.invasivepestsarenativetoWappingerCreek C.invasivepestshideinpalletsusedinshipping D.thecompaniesmakingpalletsdon'twantmorerules 2Whatcanweinferfromthepassage? A.Bugscanbeeasilyspottedbyeyes. B.Bugsruintheshippinggoodsslowly. C.Bugswon'tbotherthetreeifjustinfewnumbers. D.Bugscovertreeswithwhitesoftballsforprotection. 3WhydoesGaryLovettwanttogetridofwoodenpallets? A.Becauseinsectsmostlydieinthem. B.Becauseplasticpalletsareeco﹣friendly. C.Becausetheyarenotworthextramoney. D.Becausetheyarethemajorpestcarriers. 4Whatdoesthepassagemainlytalkabout? A.InvasivepestsareharmingplantsintheUSA. B.Effectivemeasureshavestoppedthepestinvasion. C.Congresscontributesalottodealingwithinvasivepests. D.EcosystemintheUSAispoorlydamagedbyinvasivewoods.
如图△ABC内接于⊙OAC＝BCCD是⊙O的直径与AB相交于点C过点D作EF∥AB分别交CACB的延长线于点EF连接BD． 1求证EF是⊙O的切线 2求证BD2＝AC•BF．
LettersasawayofcommunicationhavelonggivenwaytophonecallsandWeChatmessages.ButaTVshowLettersAliveishelpingbringthisoldwaytokeepintouchback1thepresent. LettersAlivetook2itideafromaUKprogramLettersLivereleasedin2013.Both3showfeaturefamousactorsandactressesbutthere4benoeye﹣catchingvisualeffectsoranyregularshowbiz娱乐圈activities.Insteadit'sjustaliveevent5remarkablelettersselectedfromawidetimespanandadiverserangeofsubjectsareread.ThereisforexampleapassionateletterfromHuangYongyutoplaywrightCaoYu30yearsagotocriticizehislackof6create. Everyletterislikeasmallpieceofhistory.Byhearingthem7readit'sasifwearebeingsentbackintimetoexperienceamomentthatwewouldotherwiseneverhavehadthechanceto. Comparedto8publishtextslettersalso9naturalcomewithapersonaltouch.AswellascelebratingthepainjoywisdomandhumorLettersAlive10committopromotingChineseliteraturesincefirstrun.
下面是一个简单的数值运算程序当输入x的值为16时输出的数值为．用科学计算器计算或笔算．
下列命题是假命题的是
如图一次函数y＝kx+b的图象与反比例函数y＝的图象在第一象限交于点A32与y轴的负半轴交于点B且OB＝4． 1求函数y＝和y＝kx+b的解析式 2结合图象直接写出不等式组0＜＜kx+b的解集．
计算+2sin30°﹣3.14﹣π0
﹣2019的绝对值是
为了庆祝中华人民共和国成立70周年某市决定开展“我和祖国共成长”主题演讲比赛某中学将参加本校选拔赛的40名选手的成绩满分为100分得分为正整数且无满分最低为75分分成五组并绘制了下列不完整的统计图表． 1表中m＝n＝ 2请在图中补全频数直方图 3甲同学的比赛成绩是40位参赛选手成绩的中位数据此推测他的成绩落在分数段内 4选拔赛中成绩在94.5分以上的选手男生和女生各占一半学校从中随机确定2名选手参加全市决赛请用列举法或树状图法求恰好是一名男生和一名女生的概率．
操作体验如图在矩形ABCD中点EF分别在边ADBC上将矩形ABCD沿直线EF折叠使点D恰好与点B重合点C落在点C′处．点P为直线EF上一动点不与EF重合过点P分别作直线BEBF的垂线垂足分别为点M和N以PMPN为邻边构造平行四边形PMQN． 1如图1求证BE＝BF 2特例感知如图2若DE＝5CF＝2当点P在线段EF上运动时求平行四边形PMQN的周长 3类比探究若DE＝aCF＝b． ①如图3当点P在线段EF的延长线上运动时试用含ab的式子表示QM与QN之间的数量关系并证明 ②如图4当点P在线段FE的延长线上运动时请直接用含ab的式子表示QM与QN之间的数量关系．不要求写证明过程
下列运算中正确的是
如图在正方形ABCD中点EF分别在边CDAD上且AF＝CE． 1求证△ABF≌△CBE 2若AB＝4AF＝1求四边形BEDF的面积．
下列立体图形中主视图是圆的是
下列立体图形中俯视图不是圆的是
下列命题是真命题的是
Whileelephantsbornwithouttusks长牙arenotunheardoftheynormallyformjust2to6percentofthepopulation.HoweverthatisnotthecaseatMozambique'sGorongosaNationalParkwhereanastonishing33percentoffemaleelephantsbornafterthecountry^civilwarendedin1992aretuskless.WhilethatmayappeartobejustacoincidenceJoycePooleanelephantbehaviorexperthasanothertheory.Theresearcherthinkswemaybewitnessingunnaturalevolutionofthespeciesduetotheconstanthuntingofelephantsforvaluableivory. Poolesaysbeforethecountry's15﹣year﹣longcivilwarthe100000﹣acreparkwashometoover4000elephants.Howeverbythetimetheconflictendedin1992about90percentofthemhadbeenkilledforivorytohelpfinanceweapons武器andmeattofeedthesoldiers.Ofthelessthan200survivorsover50percentofadultfemaleshadnotusks.Thereforeitisnotsurprisingthatthepark'stusklesselephantpopulationhasgrowngreatly. Thisisnotthefirsttimeresearchershaveobservedagreatchangeinthepopulationofelephants.AtZambia'sSouthLuangwaNationalParkandLupandeGameManagementAreaareaswhichwereheavilyhuntedinthe1970sand1980s35%ofelephants25yearsorolderand13%ofthoseyoungerthan25arenowwithouttusks.A2008studypublishedintheAfricanJournalofEcologyfoundthatthenumteroftusklessfemalesattheRuahaNationalParkinTanzaniawentfrom10.5percentin1969toalmost40percentin1989largelyduetoillegalhuntingforivory. TherecentbanonivoryinboththeUSandChinashouldhelpgetridoforatleastreduceelephanthunting.Howeverscientistsarenotsurehowlongitwilltakeforelephantswithahigherrateoftusklessfemalestochangethetrend. 1WhatistheprobablecauseofthephenomenonmentionedinParagraph1? A.Illegalhunting. B.Constantfarming. Apurecoincidence. D.Naturalevolution. 2WhydidpeoplekillsomanyelephantsduringthecivilwarinMozambique? A.Togetfundsbysellingivory. B.Todevelopnewweapons. C.Toprovidefoodforlocalpeople. D.Tomakeivoryproducts. 3Whichofthefollowinghadtheearliestrecordontusklesselephants? A.GorongonsaNationalPark. B.SouthLuangwaNationalPark. C.TheRuahaNationalPark. D.LupandeGameManagementArea. 4Whatdoestheunderlinedphrasethetrendinthelastparagraphreferto? A.Elephantsfacinggreaterdanger. B.Elephantsgrowingmoreslowly. C.Fewerfemaleelephantsstayingalive. D.Morefemaleelephantsbeingtuskless.
ItwasNewYeartime.Weweretravellinginavan货车1toystothehomeless. Whenwe2thespotsomethingcaughtmyeye.Somethingorsomeonewasmovingintherubbish.SoonI3thatitwasthehomeofapoorfamily.Thereweretwo4bothaboutmyageatthetimeandaladyIsupposedtobetheirmother.Theysatthere5. AsalittlegirlmyselfIwas6interestedinthelittlegirl.How7ourliveswere.Shelivedfortheday8throughtherubbishforsomethingtofillherstomach.Iontheotherhandwaswelllookedafterandneverhadtoworryabout9Ihadagoodeducationandthusa10future.Ilookedatthelittlegirl.Theonly11shehadwastheworn﹣outdressthatshewaswearing. SeeingthislittlegirlImadethedecisionto12adollthathadbelongedtomeforawhile.Whenthevancametoa13Isteppedoutcalledthegirloverand14thedollinherhand.Atfirstshelookedatmewith15andwasn'tcertainwhattodobutthenshesmiledandIsaw16inhereyes.Iwentbackintothevehicleandwestartedto17offandthat?swhenwerealizedthelittlegirlwasrunning18Westoppedagainandopenedthedoor.Thegirlhad19withus.Shelookeddirectlyatmeandsaidtwo20wordsThankYou. 1A.showing B.recommending C.distributing D.selling 2A.left B.changed C.chose D.approached 3A.guaranteed B.realized C.decided D.accepted 4A.boys B.children C.drivers D.adults 5A.happily B.angrily C.hopefully D.helplessly 6A.still B.less C.especially D.probably 7A.similar B.different C.difficult D.ordinary 8A.searching B.getting C.running D.breaking 9A.food B.safety C.health D.transport 10A.doubtful B.distant C.promising D.foreseeable 11A.present B.decoration C.requirement D.possession 12A.giveaway B.giveback C.handout D.handin 13A.station B.stop C.street D.signal 14A.tore B.placed C.dropped D.threw 15A.anger B.pain C.surprise D.disappointment 16A.hope B.loneliness C.anxiety D.astonishment 17A.walk B.get C.lift D.drive 18A.behind B.away C.out D.in 19A.gotalong B.comealong C.caughtup D.turnedup 20A.final B.new C.key D.simple
一元二次方程x2﹣2x+3＝0根的情况是
Wearesurroundedbymessagestryingtogetourattention.Advertiserspoliticiansandothergroupsalltrytogetustoagreewiththem.1.Propagandaisnotalwaysabadthingbutitoftenhidesthetruthaboutatopic.It'sverysimilartoadvertisingwhosegoalistogetpeopletobuysomethingwhilepropagandaistochangewhatpeoplebelieve. PropagandaTechniques Tocreatepropagandaacommontechniqueisname﹣calling.Apoliticianmightcallsomeoneatraitororliarwhichmakestheotherpersonlookbad.Anotheristhetrendtechnique.Peoplewanttobeonthesideinthefavor.2.Somepropagandaisbasedonfear.Itscarespeopleintochoosingacertainsideortakingactionwhichmightnotbebad.Anti﹣smokingcampaignsareoneexample.Theymayscarepeopleintothinkingthatiftheysmoketheywillgetcancer. 3Propagandaisusedbymanygroupssuchasbusinessespoliticiansandthegovernment.Itisspreadthroughposterstelevisionandradio.TheInternetmakesiteasytosendmessagestothewholeworld. TypesofPropaganda Politicalpropagandahasbeenaroundaslongastherehavebeenpoliticians.4.Peoplehaveuseditformanyyears.WarpropagandabeganduringWorldWarImorethan100yearsago. Toseeifpropagandaissayingthetruthpeopleneedtodoextrawork.Forexampleadsmightalwayssoundlikethey'retrue.Butbeforeyoubelievethemtrytothinkaboutwhocreatedandpaidforthem.Findoutwhytheydidit.5. A.PropagandaTargets B.PropagandaMediums C.Anotherwordforthisispropaganda D.Somostpeoplewillagreewiththosepoliticians E.Thenyoucandecideifthey'rebeinghonestornot F.Howeverreligiouspropagandawasactuallythefirstofficialone G.Peoplemightjoinsomeonewhoclaimstobepopularorwinning
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