问题 选择题

利用如图所示装置模拟电解原理在工业生产上的应用.下列说法正确的是(  )

A.氯碱工业中,X电极上反应式是4OH-4e-=2H2O+O2

B.电解精炼铜时,Z溶液中的铜离子浓度不变

C.在铁片上镀铜时,Y是纯铜

D.制取金属镁时,Z是熔融的氯化镁

答案

A、氯碱工业中,X电极连接电源正极,为电解池的阳极,溶液中的氯离子失电子生成氯气,2Cl--2e-=Cl2↑,故A错误;

B、电解精炼铜时,粗铜做阳极含有铁、锌、镍等活泼金属,精铜做阴极,电解过程中电子守恒,溶液中的铜离子浓度减少,故B错误;

C、在铁片上镀铜时,铁片做阴极为Y电极,铜做阳极为X电极,故C错误;

D、金属镁是电解熔融的氯化镁,镁阴极得到电子析出,水溶液中镁离子不放电,故D正确;

故选D.

阅读理解

Choose the best answer. 根据短文,选择最恰当的答案。

     Many people go to school for an education. They learn languages, history, politics, geography, physics,

chemistry and mathematics. Others go to school to learn a skill so that they can make a living. School education

is very important and useful. Yet, no one can learn everything from school. A teacher, no matter how much he

knows, can not teach his students everything they want to know. The teacher's job is to show his students how

to learn. He teaches them how to read and how to think. So, much more is to be learned outside school by the

students themselves.

     It is always more important to know how to study by oneself than to memorize some facts or a formula. It

is actually quite easy to learn a certain fact in history or a formula in mathematics. But it is very difficult to use

a formula in working out a math problem. Great scientists before us didn't get everything from school. Their

teachers only showed them the way. Edison didn't even finish primary school. But they were all so successful.

They invented so many things for mankind. The reason for their success is that they knew how to study. They

read books that were not taught at school. They would ask many questions as they read. They did thousands of

experiments. They worked hard all their lives, wasting not a single moment. Above all, they knew how to use

their brain.

1. People go to school to _______. [ ]

A. learn several subjects

B. make a living

C. get an education

D. learn from teachers

2. According to the passage, the most important thing a teacher should do is _______. [ ]

A. to teacher his students everything he knows

B. to know everything

C. to teach the students how to think

D. to teach the students how to study by themselves

3. To work out a math problem, you need to know ________. [ ]

A. only a certain formula

B. more than one formula

C. some facts

D. the method to solve it

4. Why were many scientists so successful? [ ]

A. They received good education.

B. They were very clever.

C. They knew how to learn.

D. They learned lots of facts and formulas.

5. How did great scientists study? [ ]

A. They read a lot of books and asked many questions while reading.

B. They did thousands of experiments.

C. They always worked hard and never wasted time.

D. All of the above.

名词解释