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问题 问答题

现有失去标签的氯化钙、硝酸银、盐酸、碳酸钠四种无色溶液，为了确定四种溶液各是什么，将它们随意编上A、B、C、D后，产生的现象如下表所示．根据实验现象回答（1）A、B、C、D溶液中溶质的化学式：

A______；B______；C______；D______；

实验顺序实验内容实验现象
①A+B没有现象发生
②B+D有气体放出
③B+C有沉淀生成
④A+D有沉淀生成
（2）D和足量B的反应方程式为______．A和D的反应方程式为______．

答案

（1）B和D有气体生成，只有碳酸钠和盐酸反应能生成气体，所以B和D是盐酸和碳酸钠，A和C是氯化钙和硝酸银；A和B没有现象发生，只有氯化钙和盐酸混合没有现象，所以所以B是盐酸，A是氯化钙，故D是碳酸钠，C是硝酸银，

故答案为：CaCl2；HCl；AgNO3；Na2CO3；

（2）碳酸钠和足量盐酸反应生成氯化钠和水、二氧化碳，反应的化学方程式为2HCl+Na2CO3=2NaCl+H2O+CO2 ↑，氯化钙和碳酸钠反应生成碳酸钙和氯化钠，反应的化学方程式为Na2CO3+CaCl2=CaCO3 ↓+2NaCl，

故答案为：2HCl+Na2CO3=2NaCl+H2O+CO2 ↑；Na2CO3+CaCl2=CaCO3 ↓+2NaCl．

单项选择题

活塞磨损最大的部位是（）。

A．活塞环槽及活塞销座孔

B．活塞裙部

C．活塞顶部
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问答题

Passage 2 Thank you, Prime Minister, for that remarkable introduction. You have very lucidly provided the context for what I am about to say this morning. It’s a great honor to be invited to speak in this historic setting. The fact that you want to hear from the Secretary-General of the United Nations at this time, and that Prime Minister Tony Blair himself suggested this public exchange of ideas suggests to me that both you and he are conscious of the remarkable moment in world history that we have reached.// Indeed, today we face threats to world order and world peace of a kind and a scale that we have not seen since the height of the Cold War. But if we can agree on ways to respond effectively to those threats, we also have a unique opportunity to build a world that will be safer, fairer and freer, for all its inhabitants. I think you glimpsed that opportunity during the G7 finance ministers’ meeting here in London last week, with its welcome emphasis on measures to attack world poverty and achieve the Millennium Development Goals.// What kind of threats do I have in mind The most obvious are terrorism and weapons of mass destruction. Many experts tell us the question is not whether, but how soon, the two will be combined -- and we see, for example, a "dirty bomb" detonated in central London, or some other major capital. The loss of life would be shocking, but as nothing to the social and economic effects. Disruption would be felt not only here but around the world. // Millions in Asia, Africa and Latin America would lose their livelihoods, because of the impact on the world economy. People in those parts of the world already face many other, more immediate threats -- hunger, disease, environmental degradation, corrupt and oppressive government, civil and ethnic conflict -- threats to which the poor are always more vulnerable than the rich. Africa, my own continent, has the worst problems of all. The hopes of many African countries have been blighted by HIV/AIDS, which is devastating the most productive age-groups and the best educated social groups, slashing life expectancy, threatening to reverse decades of economic development.// I said two years ago that this might be the most decisive moment for the international system since the United Nations was founded in 1945. I still believe that. We are living through a time of danger, but also of great opportunity. The question is, will governments muster the will to seize that opportunity, and decide on a package of reforms offering protection against threats of both kinds -- from terrorism and WMD to poverty, hunger and disease. By tackling them all at once we can make sure that no one -- North or South, rich or poor--will feel left out, and that everyone will feel an interest in implementing the whole package. //
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