问题 填空题

放置的石灰水的试剂瓶内附着一层白色固体,该固体的化学式为______,若要洗去这种固体,应向试剂瓶中加入少许的______,发生反应的化学方程式是______.

答案

氢氧化钙能与二氧化碳反应生成碳酸钙沉淀,碳酸钙能与盐酸反应生成氯化钙、水和二氧化碳从而除去,所以本题答案为:CaCO3,盐酸,CaCO3+2HCl═CaCl2+CO2↑+H2O.

阅读理解

American society is not nap (午睡)friendly . In fact , says David Dings , sleep specialist at the University of Pennsylvania School of Medicine , “There’s even a prohibition (禁止) against admitting we need sleep”. Nobody wants to be caught napping or found asleep at work . To quote a proverb : “Some sleep five hours , nature requires seven , laziness nine and wickedness(淘气的) eleven.”

The way not to fall asleep at work is to take naps when you need them . “We have to totally change our attitude toward napping ,” says Dr. William Dement of Stanford University , the godfather of sleep research .

Last year a national commission led by Dement identified(发现) an “American sleep debt” which one member said was as important as the national debt . The commission was concerned about the dangers of sleepiness : people causing industrial accidents or falling asleep while driving . This may be why we have a new sleep policy in the White House . According to recent reports , President Clinton is trying to take a half---hour snooze (瞌睡) every afternoon .

About 60 percent of American adults nap when given the opportunity . We seem to have “a mid afternoon quiet phase ,” also called “a secondary sleep gate .” Sleeping 15 minutes to two hours in the early afternoon can reduce stress and make us refreshed . Clearly , we were born to nap .

We superstars of snooze don’t nap to replace lost shut--eye or to prepare for a night shift . Rather , we “snack” on sleep ,whenever , wherever and at whatever time we feel like it . I myself have napped in buses , cars , planes and on boats ; on floors and beds ;and in libraries ,  offices and museums .

小题1:The research done by the Dement Commission shows that Americans     .

A.don’t like to take naps

B.are terribly worried about their national debt

C.think that lack of enough sleep causes many accidents

D.have caused many industrial and traffic accidents小题2:The purpose of this article is to     .

  1. warn us of the wickedness of napping 
B. explain the danger of sleepiness

C. discuss the side effects of napping

D. convince the reader of the necessity of napping

小题3:The “American sleep debt”(Line 1 , Para .3) is the result of      .

  1. the traditional misconception the Americans have about sleep
  2. the new sleep policy of the Clinton Administration
  3. the rapid development of American industry
  4. the Americans’ worry about the danger of sleepiness
小题4:The second sentence of the last paragraph tells us that it is      .

  1. preferable to have a sound sleep before a night shift
  2. good practice to eat something light before we go to bed
  3. essential (基本的) to make up for lost sleep
  4. natural to take a nap whenever we feel the need for it

多项选择题