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问题 选择题

关于H2→H2O，CO→CO2，C→CO2三种物质的转化过程，下列说法不正确的是（　　）

A．都能通过化合反应实现

B．都能通过置换反应实现

C．都能通过与CuO反应实现

D．变化前后都有元素化合价发生改变

答案

H2→H2O，CO→CO2，C→CO2的化学反应式分别是：2H2+O2

 点燃 
.
 
2H2O；2CO+O2
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2CO2；C+O2
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CO2

A、观察化学反应式可知，都是两种物质生产另一种物质，都是化合反应，故A正确；

B、观察化学反应式可知，三者都不是一种单质跟一种化合物反应生成另一种单质和另一种化合物的置换反应，故B错误；

C、氢气、一氧化碳及碳均有还原性可以还原氧化铜得到对应产物，故C正确；

D、在2H2+O2

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2H2O中，反应前单质氢和氧的化合价都是0，反应后氢元素的化合价是+1价，氧元素的化合价是-2价；2CO+O2
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2CO2中氧元素反应前化合价是0，反应后变成-2价；C+O2
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CO2中，反应前单质碳和氧的化合价是0，反应后碳元素变成+4价，氧元素变成-2价．也就是说有化合价的变化，故D正确．

故选B．

完形填空
完形填空。
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