问题 选择题

为了使(NH42SO4溶液中c(NH4+)和c(SO42-)之比更接近2:1,可向溶液中加入少量(  )

A.氢氧化钠溶液

B.硫酸

C.盐酸

D.硫酸钠溶液

答案

A、加入氢氧化钠溶液会促进铵根的水解,减少铵根离子,c(NH4+)和c(SO42-)之比小于2:1,故A错误;

B、加入硫酸能抑制铵根离子的水解,但加入了硫酸根,不能确定c(NH4+)和c(SO42-)之比更接近2:1,故B错误;

C、加入盐酸,抑制铵根离子的水解,使c(NH4+)和c(SO42-)之比更接近2:1,故C正确;

D、加入硫酸钠溶液,增加了硫酸根,c(NH4+)和c(SO42-)之比更小于2:1,故D错误;

故选C.

完形填空

The purpose of a letter of application(求职信) is to help you to “sell” yourself. It should state__16___ the job you want, and should tell what your abilities are and what you have ___17___. It should be simple, human, personal and brief without ___18___ out any necessary facts.

In writing a letter of application, keep in ___19___ that the things a possible employer is most ___20___ to want to know about are your qualifications(条件), your achievements and your aims. The opening paragraph is perhaps the most important part. ___21___ the first few sentences fail to ___22___ the reader’s attention, the rest of the letter may not be __23___ at all. Try to key your opening remarks to the needs or interests of the employer not ___24___ your own need or desires. For example, instead of beginning with “I saw your ___25___ in today’s newspaper,” you might say “I have made a careful ___26___ of your advertising during the past six months” or “I have made a survey in my neighborhood to find out how many housewives ___27___ your product and why they like it. ”

Try to ___28___ generalities. Be clear about the kind of job for which you are now ___29___. College graduates looking for their first positions often ask “What can I ___30___ in a letter? Employers want experience—which, naturally, no ___31___ has.” The answer is that everything you have ever done is ___32___.

It is important to write a good strong closing for your letter. ___33___ a specific request for an interview or give the possible employer something definite to do or expect. An excellent ___34___ is to enclose(内附) a stamped, self-addressed envelope with your letter. That makes it ___35___ for a possible employer to get in touch with you.

16. A. clearly                   B. carefully               C. obviously              D. easily

17. A. found                    B. done                     C. known                  D. heard

18. A. sending                  B. taking                   C. leaving                 D. picking

19. A. brain                     B. sight                     C. order                    D. mind

20. A. probable                B. possible                C. likely                   D. able

21. A. While                    B. Although              C. As                        D. If

22. A. pay                        B. win                      C. show                    D. fix

23. A. kept                       B. continued              C. written                 D. read

24. A. to                          B. for                       C. into                      D. from

25. A. advertisement       B. report                  C. article                   D. introduction

26. A. watch                    B. search                   C. study                    D. discussion

27. A. change                   B. make                    C. sell                       D. use

28. A. avoid                     B. remember             C. protect                  D. gain

29. A. losing                    B. applying               C. preparing              D. fitting

30. A. do                         B. write                    C. mean                    D. provide

31. A. worker                   B. beginner               C. owner                   D. manager

32. A. success                   B. development              C. practice          D. experience

33. A. Make                     B. Ask                      C. State                    D. Get

34. A. result                     B. decision                C. promise                D. idea

35. A. happier                  B. easier                   C. cheaper                 D. safer

单项选择题