问题 选择题

查处酒后驾驶采用的“便携式乙醇测量仪”以燃料电池为工作原理,在酸性环境中,理论上乙醇可以被完全氧化为CO2,但实际乙醇被氧化为X,其中一个电极的反应式为:CH3CH2OH-2e-→X+2H+.下列说法中正确的是(  )

A.电池内部H+由正极向负极移动

B.另一极的电极反应式为:O2+4e-+2H2O=4OH-

C.乙醇在正极发生反应,电子经过外电路流向负极

D.电池总反应为:2CH3CH2OH+O2→2CH3CHO+2H2O

答案

A.原电池工作时,阳离子向正极移动,故A错误;

B.电解质溶液呈酸性,正极反应式为O2+4e-+4H+=2H2O,故B错误;

C.原电池工作时,电子由负极经外电路流向正极,故C错误;

D.电池总反应与乙醇燃烧的方程式相同,应为2CH3CH2OH+O2→2CH3CHO+2H2O,故D正确.

故选D.

阅读理解

The final exam comes with June. When the exam ends(结束), the summer vacation begins. Boys and girls have about two months to relax. The summer vacation is the best time of the year for most children. The weather is usually fine. They can swim, go to summer camp or visit other places with their parents.

Of course, the beaches are good places for relaxing. Some children are lucky to live near the beach. They can play in the water. But for the children far from the sea, they go to the beaches for one or two weeks with their parents.

Why do children like spending their summer vacation on the beaches? It is because they like the sand(沙), the sun, the cool wind and the sea water. There are lots of new things to see, nice things to eat, and exciting things to do.

小题1: School children usually have exams _____.

A.in June

B.after June

C.before June

D.in July小题2:The summer vacation is about ______.

A.two weeks

B.two months

C.three months

D.two days小题3:Why do children like summer vacation?

A.because the weather is fine.

B.because it is long.

C.because the weather is fine and they can have lots of activities(活动).

D.because they can have exams.小题4:Children far from the beach can enjoy the sea ______.

A.in the evening

B.very often

C.for two months

D.for one or two weeks小题5:Which of the following is not right?

A.Children like going to the beaches only because they can see lots of new things.

B.Children like summer vacation best.

C.Children can swim and enjoy the sand, wind, and water on the beaches.

D.Children like to spend their summer vacations on beaches.

单项选择题