问题 问答题

某白色固体可能由硫酸钠、硝酸钾、硝酸铵、碳酸钙、氯化钡、硫酸铜中的一种或几种组成,做实验得以下结果:

(1)将此固体粉末加到水中,得到白色沉淀和上层无色清液; (2)过滤后,在滤出的白色沉淀里加入稀硝酸,白色沉淀部分溶解并有无色气体生成,该气体使澄清石灰水变浑浊;(3)在滤液中,加入适量的氢氧化钠溶液并加热,生成有刺激性气味的无色气体,该气体能使湿润的红色石蕊试纸变蓝.由此实验推断:该粉末中一定含有:______、______、______、______;一定不含有______;可能含有______.(填化学式)写出步骤(2)中方程式:______;______.

答案

(1)将此固体粉末加到水中,得到白色沉淀和上层无色清液,由于硫酸铜溶液是蓝色的,故一定不含有硫酸铜;得到的白色沉淀可能是碳酸钙或硫酸钡;

(2)过滤后,在滤出的白色沉淀里加入稀硝酸,白色沉淀部分溶解并有无色气体生成,该气体使澄清石灰水变浑浊,由于碳酸钙能与硝酸反应生成二氧化碳,故一定含有碳酸钙;硫酸钡是不溶于稀硝酸的白色沉淀,故一定有硫酸钡,所以原固体中含有硫酸钠和氯化钡;

(3)在滤液中,加入适量的氢氧化钠溶液并加热,生成有刺激性气味的无色气体,该气体能使湿润的红色石蕊试纸变蓝,说明生成了氨气,铵态氮肥能与碱性物质反应产生氨气,故原固体中一定含有硝酸铵;

故填:Na2SO4、NH4NO3、CaCO3、BaCl2;CuSO4;KNO3;CaCO3+2HNO3=Ca(NO32+H2O+CO2↑;Ca(OH)2+CO2=CaCO3↓+H2O.

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阅读短文,回答问题 (共5小题,每题2分,满分10分)

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World Book Day falls on April 23 every year. It was set up by the UNESCO(联合国教科文组织) in 1995 to encourage people, especially teenagers, to discover the pleasure of reading. It is also the day to honor great writer, for example, William Shakespeare, born or dead on that day.

Many countries celebrate World Book Day. Take UK as an example. On that day, millions of school children can buy books of special price, a much lower price than usual, in any bookstore. It has been done every year since 1998. World Book Day is also celebrated in China. Premier Wen Jiabao does lots of reading every day. Wen has called on people to do more reading. He suggested that young people should spend more time reading. “Book cannot change the world, but people can change the world by changing themselves through reading,” he said.

Why do people like reading? One big advantage is that reading helps us become more knowledgeable and more intelligent. Also, reading helps us to follow the latest developments of science and technology. Besides, reading gives us information about other cultures and places of the world. When we read, we may find many things that are unfamiliar to us. We would have to use our brain to think about them or do more reading to find out the answers. The more we read, the more we know. What’s more, reading is also one of the most important ways to learn a foreign language like English.

“Reading makes a full man”. Books, magazines, newspapers and other kinds of materials can help us to know more about the outside world and perfect us. So it is necessary for us to spend time on reading every day.

小题1:When is World Book Day?

小题2:In UK, what can school children do on World Book Day?

小题3:What did Premier Wen Jiabao suggest young people do?

小题4:How many advantages of reading are mentioned in the passage?

小题5:What does the passage mainly talk about?

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