钢铁生锈过程发生如下反应：①2Fe+O2+2H2O=2Fe(OH)2；②4Fe(OH)2+O2+2H2O
=4Fe(OH)3；③2Fe(OH)3=Fe2O3+3H2O。下列说法正确的是
A．反应①、②中电子转移数目相等
B．反应①中氧化剂是氧气和水
C．与铜质水龙头连接处的钢质水管不易发生腐蚀
D．钢铁在潮湿的空气中不能发生电化学腐蚀
答案：A
反应①2Fe+O2+2H2O=2Fe(OH)2中的氧化剂是O2，1molO2在反应中得到4mol电子，同样在反应②4Fe(OH)2+O2+2H2O=4Fe(OH)3中氧化剂也是O2，而且两个反应中氧气的系数都是1，因此得到的电子均是4mol，故A选项正确B选项错误。钢质水管与铜质水龙头连接后形成原电池，其中钢质水管做负极被腐蚀，故C选项错误。钢铁在潮湿的空气中容易发生电化学腐蚀，而且主要是发生吸氧腐蚀，因此D选项错误。
点评：原电池知识是高中电化学的重点也是难点，难度不大，解题的关键是要正确区分正负极的电极反应，掌握原电池原理。
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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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