问题 选择题

海洋中有丰富的食品、矿产、能源、药物和水产资源等(如下图所示),下列有关说法正确的是

 

A.第①步中除去粗盐中的SO42-、Ca2+、Mg2+、Fe3+等杂质,加入的药品顺序可以为碳酸钠溶液、NaOH溶液BaCl2溶液,过滤后加盐酸

B.第②步中结晶出的MgCl2·6H2O可在HCl气流中加热分解制无水MgCl2

C.在第③④⑤步中溴元素均被氧化

D.第⑤步涉及的分离操作有过滤、萃取、蒸馏

答案

答案:B

题目分析:A.第①步中除去粗盐中的SO42-、Ca2+、Mg2+、Fe3+等杂质,加入的药品顺序可以为NaOH溶液、BaCl2溶液、碳酸钠溶液,过滤后加盐酸;也可以是BaCl2溶液、NaOH溶液、碳酸钠溶液,过滤后加盐酸。总之就是SO42-离子要在Ca2+之前除去,以使引入的过量的Ba2+与Ca2+一同用CO32-除去,减少实验步骤。错误。B.MgCl2是强碱弱酸盐,加热容易发生水解反应,HCl挥发逸出而得到Mg(OH)2,使产物不纯。实验第②步中结晶出的MgCl2·6H2O可在HCl气流中加热分解就可以抑制其水解来制无水MgCl2。正确。C.化合价升高,失去电子,被氧化;化合价降低,得到电子,被还原。在第③中Br化合价升高,被氧化;在④中发生反应:Br2+SO2+2H2O=H2SO4+2HBr。Br化合价降低,被还原。在⑤步中在HBr→Br2.化合价升高,被氧化。错误。D.第⑤步涉及的分离操作有蒸发、浓缩、蒸馏。错误。

单项选择题

The appeal of advertising to buying motives can have both negative and positive effects. Consumers may be convinced to buy a product of poor quality or high price because of an advertisement. For example, some advertisers have appealed to people’s desire for better fuel economy for their cars by advertising automotive products that improve gasoline mileage. Some of the products work. Others are worthless and a waste of consumers’ money.

Sometimes advertising is intentionally misleading. A few years ago, a brand of bread was offered to dieters (节食者) with the message that there were fewer calories (热量单位,卡路里) in every slice. It turned out that the bread was not dietetic (适合节食的), but just regular bread. There were fewer calories because it was sliced very thin, but there were the same number of calories in every loaf.

On the positive side, emotional appeals may respond to a consumer’s real concerns, considering fire insurance. Fire insurance may be sold by appealing to fear of loss. But fear of loss is the real reason for fire insurance. The security of knowing that property is protected by insurance makes the purchase of fire insurance a worthwhile investment for most people. If consumers consider the quality of the insurance plans as well as the message in the ads, they will benefit from the advertising.

Each consumer must evaluate her or his own situation. Are the benefits of the product important enough to justify buying it Advertising is intended to appeal to consumers, but it does not force them to buy the product. Consumers still control the final buying decision.

It can be inferred from the passage that a smart consumer should()

A. think carefully about the benefits described in the advertisements

B. guard against the deceiving nature of advertisements

C. be familiar with various advertising strategies

D. avoid buying products that have p emotional appeal

问答题 简答题