问题 选择题

常温下,加水稀释时

c(H+)
c(OH-)
值明显增大的溶液中,一定能大量共存的离子组是(  )

①K+、Cl-、NO3-、AlO2-             ②K+、Fe2+、I-、SO42-

③Ba2+、OH-、NO3-、Na+             ④Na+、Ca2+、Al3+、Cl-

A.①②

B.①③

C.②④

D.②③

答案

①AlO2- 水解的反应为:AlO2-+2H2O⇌Al(OH)3+OH-,溶液呈碱性,加水稀释,AlO2-浓度越稀,水解程度越大,电离出的氢氧根离子数目越多,但盐类水解的程度是相当小的,其影响程度不及加水对溶液酸碱性的影响大,即氢氧根离子数目增多不及溶液体积的增加,溶液总体趋势,碱性减弱,c(H+)/c(OH-)值明显增大,故①正确;

 ②Fe2+水解的反应为:Fe2++2H2O⇌Fe(OH)2+2H+,溶液呈酸性,加水稀释时,Fe2+浓度越稀,水解程度越大,电离出的氢离子数目越多,但盐类水解的程度是相当小的,其影响程度不及加水对溶液酸碱性的影响大,即氢离子数目增多不及溶液体积的增加,溶液总体趋势酸性减弱,c(H+)/c(OH-)值明显减少,故②错误;

③因有OH-,溶液呈强碱性,加水稀释时,溶液碱性减弱.c(H+)/c(OH-)值明显增大,故③正确;

④Al3+水解的反应为:,Al3++3H2O⇌Al(OH)3+3H+,溶液呈酸性,加水稀释时,水解程度越大,电离出的氢离子数目越多,但盐类水解的程度是相当小的,其影响程度不及加水对溶液酸碱性的影响大,即氢离子数目增多不及溶液体积的增加,溶液总体趋势酸性减弱,c(H+)/c(OH-)值明显减少,故④错误;

故选B.

完形填空

Being alone in outer space can be frightening. That is one reason why astronauts on solo (单独的) space flights were given plenty of work to keep them  21 . They were also constant communication with people on the earth.  22 , being with people from whom you cannot get away might be even harder than being alone. This is what happens on long submarine (潜水艇) voyages. It will also happen on  23  space flights in the future. Will there be special problem of adjustment under such conditions?

Scientists have studied the reactions of men to one another during long submarine voyages. They have found that the longer the voyage lasts, the more serious the problem of 24  is. When men are  25  together for a long period, they begin to feel uneasy. Everyone has little habits of speaking and behaving that are ordinarily acceptable. In the limited space over a long period of time, however, these little habits may become very  26 .

Apparently, although no one wants to be  27  all the time, everyone needs some degree of privacy. When people are enclosed together, they are in what is called a stress situation. That means that they are under an unusual amount of  28  or stress.

People who are well-adjusted are able to  29 stress situations better than others. That is one reason why so much care is taken in  30  our astronauts. These men undergo a long period of testing and training. One of the things tested is their behavior under stress.

21. A. tired                    B. asleep                 C. conscious            D. busy

22. A. So far                  B. After all              C. However             D. Therefore

23. A. long                    B. fast                     C. dangerous            D. direct

24. A. fuel                     B. entertainment       C. adjustment           D. health

25. A. shut up                B. held up               C. brought up          D. picked up

26. A. pleasing               B. annoying             C. common              D. valuable

27. A. noisy                   B. alone                  C. personal              D. sociable

28. A. emphasis              B. conflict               C. power                 D. pressure

29. A. handle                 B. create                  C. affect                  D. investigate

30. A. becoming             B. choosing             C. ordering              D. promoting

问答题 简答题