[单选题]— Isn"t it a surprise that I happened to meet Emily at Doris" birthday party last weekend— If my memory serves me correctly, you _____?each other for exactly three years.A. hadn"t seen B. haven"t seen C. didn"t seeD. don"t see
[单选题]The instructors life will improve instantly he ________ the parttime job.[ ]A. gotB. will getC. getsD. would get
[单选题]将淀粉水解并用氢氧化铜浊液检验其水解产物的实验中,要进行的主要操作如下:①加热;②滴入稀硫酸;③加入新制的Cu(OH)2浊液;④加NaOH溶液中和.以上各步骤的先后顺序的正确排列是( )A.①②③④B.②①④③C.②①④③①D.③④①②①
[单选题]“绿色化学”是指从技术、经济上设计可行的化学反应,尽可能减少对环境的负作用,下列化学反应,不符合“绿色化学”概念的是[ ]A.消除硫酸厂尾气的SO2:SO2+2NH3+H2O = (NH4)2SO3 B.消除硝酸厂尾气中的氮氧化合物:NO+NO2+2NaOH = 2NaNO2+H2O C.制CuSO4:D.制CuSO4:2Cu+O2 = 2CuO;CuO+H2SO4(稀)= CuSO4+H2O
[单选题]— How long do you want me to heat the oil— Heat it till it _____?to smoke. [ ]A. would beginB. begins C. will begin D. began
[单选题]将淀粉水解,并用新制的氢氧化铜悬浊液检验其水解产物的实验中,要进行的主要操作是①加热?②滴入稀硫酸③加入新制的氢氧化铜悬浊液?④加入足量的氢氧化钠溶液A.①→②→③→④→①B.②→①→④→③→①C.②→④→①→③→①D.③→④→①→②→①
[单选题]莽草酸是一种合成治疗禽流感药物达菲的原料,鞣酸存在于苹果、生石榴等植物中.下列关于这两种有机化合物的说法正确的是[ ]A.莽草酸不能与溴水反应B.两种酸遇三氯化铁溶液都显色C.鞣酸分子与莽草酸分子相比多了两个碳碳双键 D.等物质的量的两种酸与足量金属钠反应产生氢气的量相同
[单选题]实验中欲量取50.00 mL KMnO4溶液可选用的仪器是[ ]A.50 mL量筒 B.10 mL量筒C.50 mL酸式滴定管D.50 mL碱式滴定管
[单选题]下列各组中两个化学反应,属于同一反应类型的一组是A.由苯制硝基苯;由苯制环己烷B.由乙烯制1,2-二溴乙烷;由乙烷制一氯乙烷C.乙烯使溴水褪色;乙烯使酸性高锰酸钾溶液褪色D.由苯制溴苯;由乙酸与乙醇反应制乙酸乙酯
[单选题]When you are home, give a call to let me know you ________ safely.[ ]A. are arrivingB. have arrivedC. had arrivedD. will arrive
[多选题]长期吸食或注射毒品会危及人体健康,下列各组中属于毒品的是( )A.冰毒B.海洛因C.大麻D.鸦片
[单选题]蛋白质的下列哪个性质可以用于蛋白质的提纯分离( )A.水解B.盐析C.变性D.颜色反应
[单选题]Email,as well as telephones ________ an important part in daily communication.[ ]A. is playingB. have playedC. are playingD. play
[单选题]塑料的使用大大方便了人类的生活,但由此也带来了严重的“白色污染”.下列对废弃塑料制品的处理方法中最为恰当的是( )A.焚烧B.粉碎后深埋C.倾倒在海洋中D.用化学方法加工成防水涂料或汽油
[单选题]下列物质中,能在X射线透视肠胃时用作“钡餐”的是).A.BaSO4B.BaCO3C.BaCl2 D.NaCl
[单选题]上海世博园地区的一座大型钢铁厂搬迁后,附近居民将不再受到该厂产生的棕红色烟雾的困扰.你估计这一空气污染物可能含有[ ]A.FeO粉尘 B.P2O5粉尘 C.Fe2O3粉尘 D.SiO2粉尘
[单选题]When I called you this morning, nobody answered the phone. Where ______?[ ]A. did you go B. have you goneC. were you D. had you been
[单选题]Listen! The baby ______ in the next room.A. cryingB. cried C. is crying D. cries
[单选题]下列有机物水解时断键处(用虚线表示)正确的是 [ ]A.B.C.D.
[单选题]It is said in the book that Thomas Edison (1847-1931)? _____ the world leading inventor for sixty years . ( )A. would beB. has been C. had been D. was
[单选题]绿色化学的核心是反应过程的绿色化,即要求原料物质中的所有原子完全被利用且全部转入期望的产品中,下列过程不符合这一思想的是 ( )A.氢气、CO乙酸乙酯 :2H2+2COCH3COOCH2CH3B.烯烃与水煤气发生反应:RCH=CH2+CO+H2RCH2CH2CHO C.乙醇被氧气催化氧化得乙醛D.氯乙烯合成聚氯乙烯