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问题 填空题

写出下列反应的符号表达式，并注明反应类型：

（1）硫燃烧______；______．

（2）加热高锰酸钾制取氧气______；______．

（3）双氧水制氧气______；______．

（4）铁丝在氧气中燃烧______；______．

答案

（1）硫燃烧生成二氧化硫，两种物质生成一种物质，属于化合反应，故答案为：S+O2

 点燃 
.
 
SO2； 化合反应．

（2）加热高锰酸钾生成锰酸钾、二氧化锰和氧气，一种物质生成三种物质，属于分解反应，故答案为：2KMnO4

  △  
.
 
K2MnO4+MnO2+O2↑； 分解反应．

（3）双氧水在二氧化锰的催化作用下生成水和氧气，一种物质生成两种物质，属于分解反应，故答案为：2H2O2

 MnO2 
.
 
2H2O+O2↑； 分解反应．

（4）铁丝在氧气中燃烧生成四氧化三铁，两种物质生成一种物质，属于化合反应，故答案为：3Fe+2O2

 点燃 
.
 
Fe3O4； 化合反应．

单项选择题

（一） Friends play an important part in our lives, and although we may take the friendship for granted, we often don’t clearly understand how we make friends. While we get on well with a number of people, we are usually friends with only a very few, for example, the average among students is about 6 per person. In all the eases of friendly relationships, two people like one another and enjoy being together, but beyond that, the degree of intimacy between them and the reasons for their shared interest vary enormously. As we get to know people we take into account things like age, race, economic condition, social position, and intelligence. Although these factors are not of prime importance, it is more difficult to get on with people when there is a marked difference in age and background. Some friendly relationships can be kept on argument and discussion, but it is usual for close friends to have similar ideas and beliefs, to have attitudes and interests in common--they often talk about ’ being on the same wavelength’. It generally takes time to reach this point. And the more intimately involved people become, the more they rely on one another. People want to do friends favors and hate to break a promise. Equally, friends have to learn to put up with annoying habits and to tolerate differences of opinion. In contrast with marriage, there are no friendship ceremonies to strengthen the association between two people. But the supporting and understanding of each other that results from shared experiences and emotions does seem to create a powerful bond, which can overcome differences in background, and break down barriers of age, class or race.

Which of the following is not implied in the passage ______

A．Even friends may have differences of opinion.

B．Friends never argue with each other.

C．It generally takes time for people to become close friends.

D．Someone’s habits may annoy his friends.
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问答题 简答题

简述仪表互感器的作用？
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