问题 计算题

A和B两种有机物,各取0.1mol 充分燃烧,都生成4.48L CO2(标准状况)和3.6g H2O。已知A对氢气的相对密度为14,B中碳元素的质量分数为40%,且B的水溶液具有导电性。试求A和B的分子式,并写出它们的结构简式

答案

则化合物分子式为C2H4Ox

M(A)=DM(H2)=14×2=28

则A为C2H4,结构简式:CH2=CH2

24+4+16x=60;x=2

则B为C2H4O2,依题意,B的结构简式为CH3COOH

单项选择题
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     [1] Nowadays, researchers from the University of Maryland found that nearly four in five students have depression,panic,confusion and extreme isolation when they are forced to keep away from technology for a day.The study concluded that "most students failed to go the full 24 hours without media". They have

been addicted to the modem technology.

     [2] In this research, almost 1,000 university students from 12 campuses in 10 countries, including

Britain, America and China, have been interviewed. Most of them were unable to avoid technology for one full day. The researchers concluded that, college students at campuses across the globe admitted being

"addicted" to modem technology such as mobile phones, laptops and televisions as well as social

networking such as Facebook and Twitter. An American college student told of his great desire when he

was forced to keep away from the media. He even said it           "cocaine addiction".

     [3]The research also found students used "nearly the same words to describe their reactions when they were away from the media". These included emotions such as confusion,anxiety, insecurity, jealousness,

anger, loneliness, dependence and depression.

     [4] Professor Susan Moeller, who led the research, said technology had changed the students'

relationships. "Students talked about how seary(可怕的) it was when there is no technology, how

addicted they were to it," she said. "They expected the frustration without the media. But they didn't

expect to have the psychological effects, to be lonely, to be panicked, the anxiety, literally heart

palpitations (心悸). Technology provides the social network for young people today and they have spent their entire lives being 'plugged in ' . "

1.What's the main idea of the text? (no more than 10 words)

____________________________________________________________________________

2.How will most students feel if they keep away from technology for 24 hours? (no more than 9 words)

________________________________ ____________________________________________

3.Fill in the blank in Paragraph 2 with proper words. (no more than 4 words)

____________________________________________________________________________

4.What does the underlined word "These" in Paragraph 3 probably refer to? (no more than 10 words)

____________________________________________________________________________

5.Complete the following statement with proper words. (no more than 2 words)

The youth have access to social network nowadays with the help of ________which they are addicted to and can't get away from.