汽车尾气中的CO在四氧化三钴（Co3O4）纳米棒的催化作用下，低温即与O2反应生成CO2。下列关于该反应的说法中，正确的是
A．该反应是分解反应
B．反应前后Co3O4化学性质改变
C．反应前后碳元素的化合价不变
D．可降低汽车尾气对大气的污染
答案：D
题目分析：根据题意结合所学知识分析。
A、根据题意可知，反应物为一氧化碳和氧气（两种），而生成物为二氧化碳（一种），故该反应属于化合反应，故A错误；
B、催化剂在化学反应前后，质量和化学性质都不变，所以反应前后Co3O4的化学性质不变，故B错误；
C、反应物一氧化碳中碳元素的化合价为+2价，而生成物二氧化碳中碳元素的化合价为+4价，故C错误；
D、通过Co3O4的催化可以将一氧化碳转化为二氧化碳，所以可以减少对空气的污染，故D正确。故选D
点评：本题难度不大，掌握化合反应的特征、催化剂的特征、利用化合价的原则计算指定元素的化合价的方法是正确解答本题的关键。
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| Which is the best way to learn a foreign language? We 1 that we all learned our own language well when we were children. If we can learn a second language in the same way, it won't seem to be so 2 . Think of what small children do. They listen to 3 people say and they try to imitate (模仿) what they 4 . When they want something, they have to 5 for it. They are using languages, taking 6 it all the time. If 7 use a second language like this all the time, they will learn it more 8 . It is also important to remember that we learn our own language by hearing people speaking it, 9 by seeing what they write. In school, though you learn to hear and speak, to read and write, you must learn all new words through the ears. You can read them, spell them and write them 10 . | ||||
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