问题 实验题

某化学兴趣小组在实验室做了如图所示的A、B两个实验.

(1)B实验中发生反应的化学方程式为                            

(2)A、B两个实验结束后,小明同学将两支试管中的物质同时加入一纯净的烧杯中(如图C所示),混合后,观察到烧杯中有蓝色沉淀.同学们将烧杯内的物质过滤,对所得滤液中溶质的成分进行探究.

【猜想】

小明猜想:滤液中的溶质是Na2SO4、CuSO4

小光猜想:滤液中的溶质是Na2SO4、NaOH;

小英猜想:滤液中的溶质是Na2SO4、CuSO4、H2SO4

你的猜想:滤液中的溶质还可能是         

【讨论】你认为      的猜想一定不合理.如果滤液为无色,还可排除      的猜想,理由是                              

【实验】若小光的猜想正确,请完成下表的方案.

实验步骤预想的实验现象实验结论
取少量滤液与试管中,滴入            小光的猜想正确
 

答案

(1)2NaOH+H2SO4=Na2SO4+2H2O

(2)【猜想】Na2SO4

【讨论】小英,小明,滤液中含有硫酸铜,溶液呈蓝色

【实验】

实验步骤预期的实验现象
酚酞溶液无色溶液变红色
 

题目分析:(1)氢氧化钠能与硫酸反应生成硫酸钠和水,故填:2NaOH+H2SO4=Na2SO4+2H2O;

(2)硫酸铜能与氢氧化钠反应生成氢氧化铜沉淀和硫酸钠,氢氧化钠能与硫酸反应生成硫酸钠,故滤液中一定含有硫酸钠,故填:Na2SO4

由于烧杯中含有蓝色沉淀氢氧化铜,而氢氧化铜能与硫酸反应生成易溶于水的硫酸铜,故一定不会含有硫酸,所以小英的猜想一定不正确;硫酸铜溶液是蓝色的,若滤液是无色的,则小明的猜想不正确,故填:小英,小明,滤液中含有硫酸铜,溶液呈蓝色;

小光的猜想中,含有氢氧化钠,氢氧化钠的水溶液呈碱性,能使酚酞试液变红,故可以使用酚酞试液来证明,故填:

实验步骤预期的实验现象
酚酞溶液无色溶液变红色
 

点评:本题考查了常见的物质的性质,完成此题,可以依据已有的知识进行.要求同学们加强对基础知识的储备,以便灵活应用.

单项选择题

Jet lag is back on the agenda for business travelers, especially as long-haul international traffic picks up again.

There is endless advice online about jet lag. Drugs are frequently mentioned, and a recent favorite is Nuvigil, used to treat excessive sleepiness. Nuvigil’s manufacturer, Cephablon, has so far not succeeded in obtaining government approval for its plan to market the drug as a remedy forjet lag.

But the approach I hear most often from long-haul travelers involves diet and preparation. " Why would you take a pill that your body then has to shake off " said Lynne Waller Scanlon, the author, with Charles F. Ehret, of Overcoming Jet Lag, which was a best seller in the mid-1980s but went out of print until she revised and republished it last year under a snappier title, The Cure for Jet Lag.

The book lays out a treatment system for jet lag based on pre-trip diet and conditioning to reset the body’s internal clock. The book suggests resetting the body clock so that it will be in sync with the time at the destination. One to three days before a trip, the authors suggest low-calorie meals. In flight, avoid or strictly limit alcohol, and use coffee or tea to persuade the body clock that it’s daytime. If it’s morning after flying all night, resist sleep and " flood your eyes with daylight " , they suggest.

While all long-haul travel can cause normal fatigue, travel across time zones causes the body to react with the most pronounced effects of jet lag, including disorientation and a general sense of discomfort.

In the last few years, the global airlines have put more emphasis on accommodating the need for in-flight sleep—at least in the business and first—class cabins, where international airlines earn most of their revenue. But at the same time, international airlines also promote extensive in-flight entertainment selections, as well as high-end menus, including quality wine lists, in premium classes. Indulging in these would seem to work against dietary treatment to combat jet lag. But Ms. Scanlon says recovery is nevertheless attainable.

" What do you do if you can’t implement this program ahead of the trip, or if you’ve blown it and had a complete debauch on the plane " she said, " Well, when you get off that plane, you get on the program right away. It may not be perfect, but you will feel much, much better.

It is indicated in Paragraph 2 that()

A. we cannot find enough advice about jet lag

B. people often talk about drugs for jet lag

C. Nuvigil is the best drug for jet lag

D. if you sleep too much after a long flight, you can take Nuvigil as a treatment

填空题