问题 填空题

如图是氯化钠的晶胞示意图,回答如下问题

(1)在NaCl晶体中,与每个Cl-距离等同且距离最近的几个Na+所围成的空间几何构型为__________。 A.正四面体 B.正六面体 C.正八面体 D.正十二面体

(2)NaCl晶体中不存在分子,但是当温度达到1686 K时,NaCl晶体形成气体,并以分子形式存在。现有29.25g NaCl晶体,强热使其气化,测的气体体积为5.6L(已折算成标准状况)则此时氯化钠气体的化学式为_____________。

(3)随着科学技术的发展,阿伏加德罗常数的测定手段越来越多,测定的精确度也越来越高。现有一种简单可行的测定方法,具体步骤为:

①将固体NaCl细粒干燥后,准确称取ag NaCl固体并转移到定容容器A中;

②用滴定管向A仪器中加苯,不断振荡,继续加苯至A仪器的刻度,计算出NaCl固体的体积为V cm3。步骤①中A仪器最好使用_______________。

A.量筒 B.烧杯 C.容量瓶 D.试管

(4)已知NaCl晶体中,距离最近的Na+与Cl-间的平均距离为bcm,用上述测定方法测得的阿伏加德罗常数NA的表达式为______________________。(用含V、a、b的代数式表示)

答案

(1)C

(2) (NaCl)2 (写成Na2Cl2也可以)

(3)C

(4)58.5V/(2ab3)

完形填空

Ero Carrera is watching the computer screen in a lab in California as he tracks a new computer virus slowly circling the globe, targeting cell phones. Working from the US office of the Finnish computer   21  firm, Carrera knows this virus could be the start of something big and   22  . He’s one of a couple of hundred “virus hunters” worldwide who guard computers and cell phones from   23 . That’s the job for these unlikely action heroes of the Internet age, where quick and curious minds are more important than strong   24 .

Carrera works with Tzvetan Chaliavski to form the two-man team in California. Like that of other employees in the anti-virus companies in the world, their work is at the battle front of providing   25  from the damaging of computer virus, worms and Trojans. They break down software to discover a new virus and crack its code. Then they   26  and ship out a software update to customers. Roughly 300 new samples of viruses await the pair on a(n)  27  day.

Carrera has created a mathematical formula(公式), to   28  easily the software structure of viruses. With it, he is better able to compare the many variants(变种) and families of malware(恶意软件). To his   29 , Chaliavski, it doesn’t even matter why someone would create a virus. All that   30  is the hunt.

21. A. advertising         B. commercial                    C. printing                   D. security

22. A. admiring             B. exciting                   C. inviting                   D. threatening

23. A. attack                B. bombing                 C. competition                    D. struggle

24. A. heads                 B. feelings                   C. muscles                   D. spirits

25. A. access                B. contact                    C. measures                 D. protection

26. A. copy                  B. create                  C. delete                  D. download

27. A. average               B. original                   C. previous                  D. special

28. A. get off               B. make out                 C. pick up                   D. take in

29. A. assistant              B. manager                  C. partner                           D. secretary

30. A. ignores               B. matters                    C. overlooks                D. rejects

单项选择题