问题 选择题

下列过程中,需要通电才能进行的是(  )

①电离②电解③电泳④电镀⑤电解精炼⑥电化学腐蚀.

A.①②④⑥

B.②④⑤⑥

C.①③④⑤

D.②③④⑤

答案

①电离是电解质在水溶液中离解出自由移动离子的过程,不需要通电,故①错误;

②电解池是外加电源强迫下的氧化还原反应,必须加外加电源,故②正确;

③③电泳是胶体分散质微粒在电源作用下的定向移动,证明胶体粒子所带的电性,需要通电,故③正确;

④电镀池实质是一个电解池,必须加外加电源,故④正确;

⑤电解精炼铜是借助电解原理实现粗铜的提纯的,必须加外加电源,故⑤正确;

⑥电化学腐蚀原理是原电池原理,原电池中不含电源,是自发进行的氧化还原反应,故⑥错误.

故选D.

问答题
单项选择题 案例分析题

Questions 11 to 15 are based on the following passage.

Scratchy throats, stuffy noses and body aches all spell misery, but being able to tell if the cause is a cold or flu (流感) may make a difference in how long the misery lasts.

The American Lung Association (ALA) has issued new guidelines on combating colds and the flu, and one of the keys is being able to quickly tell the two apart. That’s because the prescription drugs available for the flu need to be taken soon after the illness sets in. As for colds, the sooner a person starts taking over-the-counter remedy, the sooner relief will come.

The common cold and the flu are both caused by viruses. More than 200 viruses can cause cold symptoms, while the flu is caused by three viruses—flu A, B and C. There is no cure for either illness, but the flu can be prevented by the flu vaccine (疫苗), which is, for most people, the best way to fight the flu, according to the ALA.

But if the flu does strike, quick action can help. Although the flu and common cold have many similarities, there are some obvious signs to look for.

Cold symptoms such as stuffy nose, runny nose and scratchy throat typically develop gradually, and adults and teens often do not get a fever. On the other hand, fever is one of the characteristic features of the flu for all ages. And in general, flu symptoms including fever and chills, sore throat and body aches come on suddenly and are more severe than cold symptoms.

The ALA notes that it may be particularly difficult to tell when infants and preschool age children have the flu. It advises parents to call the doctor if their small children have flu-like symptoms.

Both cold and flu symptoms can be eased with over-the-counter medications as well. However, children and teens with a cold or flu should not take aspirin for pain relief because of the risk of Reye syndrome (综合症),a rare but serious condition of the liver and central nervous system.

There is, of course, no vaccine for the common cold. But frequent hand washing and avoiding close contact with people who have colds can reduce the likelihood of catching one.

 

We learn from the passage that ()

A.one doesn’t need to take any medicine if he has a cold or the flu

B.aspirin should not be included in over-the-counter medicines for the flu

C.delayed treatment of the flu will harm the liver and central nervous system

D.over-the-counter drugs can be taken to ease the misery caused by a cold or the flu