已知复数z=-1+i(为虚数单位),计算:z•.zz-.z=______.

题型:填空题

问题:

已知复数z=-1+i(为虚数单位),计算:
z•
.
z
z-
.
z
=______.
考点:复数的四则运算
题型:填空题

Jan:I have new photos of my family, but they’ re not very good. This is my sister…

Mark:Where is she?  Is she at the library?

Jan:No, she’ s in the living room. She s doing her homework. And that s my brother.

Mark:Is he doing his homework, too? What’s he eating?

Jan:He’ s watching a scary movie on TV and eating french fries.

This is a picture of my aunt and my mother.

Mark:Is that -your mother in the pool?

Jan:No, that’s my aunt. My mother can’t swim. And this is my mother and my aunt at the shop. They really like shopping and eating at the shop. Mark: Interesting photos.

1. The pictures are ______.

A. good   B. interesting   C. scary

2. Jan’ s sister is doing her homework ______.

A. at the library   B. at the pool   C. in the living room

3. Jan’ s brother isn’ t ______.

A. doing his homework   B. watching TV    C. eating french fries

4. Jan’ s ______ can’ t swim.

A. sister   B. mother   C. aunt

5. Jan’ s mother and aunt like ______ at the shop.

A. eating french fries   B. shopping    C. swimming

题型:填空题

如图所示的电路中,电源内阻不能忽略,闭合开关S,当滑动变阻器的滑动触头向上移动的过程中,以下判断中正确的是(  )

A.电源两极间的电压变小

B.电阻R2两端的电压变大

C.电流表的示数变大

D.电压表的示数变大

题型:填空题

醇与氢卤酸反应是制备卤代烃的重要方法。实验室制备溴乙烷和1-溴丁烷的反应如下:

NaBr+ H2SO4==HBr+ NaHSO4 ① R-OH + HBr=R-Br+H2O ②

可能存在的副反应有:醇在浓硫酸的存在下脱水生成烯和醚,Br-被浓硫酸氧化为Br2等。有关数据列表如下

请解答下列问题:

(1)在溴乙烷和1-溴丁烷的制备实验中,下列仪器最不可能用到的是_________。(填字母)

a.圆底烧瓶 b.量筒 c.锥形瓶 d.布氏漏斗

(2)溴代烃的水溶性_______(填“大于”、“等于”或“小于”)相应的醇,其原因是_____________________________。

(3)将1-溴丁烷粗产品置于分液漏斗中加水,振荡后静置,产物在____ (填“上层”、“下层”或“不分层”)。

(4)制备操作中,加入的浓硫酸必须进行稀释,其目的是____________。(填字母)

a.减少副产物烯和醚的生成 b.减少Br2的生成 c.减少HBr的挥发 d.水是反应的催化剂

(5)欲除去溴代烷中的少量杂质Br2,下列物质中最适合的是___________。(填字母)

a. NaI b.NaOH c.NaHSO3 d.KCl

(6)在制备溴乙烷时,采用边反应边蒸出产物的方法,其有利于_____________________;但在制备1-溴丁烷时却不能边反应边蒸出产物,其原因是___________________。

题型:填空题

玻璃板面上的料疙瘩是怎样产生的?

题型:填空题

下列关于参数传递的说法中,正确的是

A.当实参的数量少于形参的数量时,多余的形参初值取逻辑假.

B.当实参的数量大于形参的数量时,多余的实参被忽略

C.实参和形参的数量必须相等

D.答案A、B均正确

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