问题 选择题

下图是a、b两种固体物质的溶解度曲线,下列说法中正确的是(    )

A.a中含有少量b时,一般用蒸发溶剂的方法提纯a

B.t℃时,a、b饱和溶液中含有的溶质质量a大于b

C.当温度大于t℃时,a溶液一定比b溶液浓

D.a物质的溶解度受温度变化的影响较大

答案

答案:A

   

题目分析:A、从溶解度曲线可看出,a的溶解度随温度的升高变化较大,而b的溶解度随温度的升高而变化较小,故a中含有少量b时,可以用冷却热饱和溶液的方法提纯a,错误,B、t℃时,a物质的溶解度大于b物质的溶解度,故等质量a、b饱和溶液中含有的溶质质量a大于b,但没有指明是等质量,错误, C、当温度大于t℃时,a物质的溶解度大于b物质的溶解度,但a溶液不一定比b溶液浓,因为没有讲清楚是否是饱和溶液,错误,D、从溶解度曲线可看出,a物质的溶解度受温度变化的影响较大,正确,故选A

单项选择题 案例分析题
单项选择题

The worst thing about television and radio is that they entertain us, saving us the trouble of entertaining ourselves.

Which of the following is NOT the reason for the decline in amateur singing
A. It is easier for people to please themselves with songs through TV and radio.
B. Amateurs feel embarrassed for they cannot sing as well as the professionals.
C. People don’t want to take the trouble to sing songs themselves.
D. Famous and talented musicians can easily be met.

A hundred years ago, before all these devices were invented, if a person wanted to entertain himself with a song or a piece of music, he would have to do the singing himself or pick up a violin and play it. Now, all he has to do is turn on the radio or TV. As a result, singing and music have declined.
Italians used to sing all the time. Now, they only do it in Hollywood movies, Indian movies are mostly a series of songs and dances trapped around silly stories. As a result, they don’t do much singing in Indian villages anymore. Indeed, ever since radio first came to life, there has been a terrible decline in amateur (业余的) singing throughout the world.
There are two reasons for this sad decline. One, human beings are astonishingly lazy. Put a lift in a building, and people would rather take it than climb even two flights of steps. Similarly, invent a machine that sings, and people would rather let the machine sing than sing themselves. The other reason is that people are easily embarrassed. When there is a famous, talented musician readily available by pushing a button, which amateur violinist or pianist would want to try to entertain family or friends by himself
These earnest reflections came to me recently when two CDs arrived in the mail. They are historic recordings of famous writers reading their own works. It was thrilling to hear the voices from a long dead past in the late 19th century. But today, reading out loud anything is no longer common. Today, we sing songs to our children until they are about two, we read simple books to them till they are about five, and once they have learnt to read themselves, we become deaf. We’re alive only to the sound of the TV and the stereo (立体声音响).
I count myself extremely lucky to have been born before TV became so common: I was about six before TV appeared. To keep us entertained my mother had to do a good deal of singing and tell us endless tales. It was the same in many other homes. People spoke a language; they sang it, they recited it; it was something they could feel.
Professional actors’ performance is extraordinarily revealing. But I still prefer my own reading, because it’s mine. For the same reason, people find karaoke (卡拉OK) liberating. It is almost the only electronic thing that gives them back their own voice. Even if their voices are hopelessly out of tune, at least it is meaningful self-entertainment.