题干

某化学实验小组为验证常见还原剂SO2、I、Fe2+的还原性强弱的顺序为:SO2>I>Fe2+,用图所示装置进行实验(加热和夹持装置已略,气密性已检验).

(1)上述实验需要加热的装置是____ 

(2)A中反应的化学方程式为____  

(3)D中,烧杯盛放的是____ 

(4)实验开始时,关闭K1,打开K2,通入少量氯气,写出B中发生反应的离子方程式____  

①为验证I的还原性比Fe2+强,取(4)后B中的少量溶液于试管中,应再往试管中滴入____ 溶液,现象是____ 

②在(4)后,为了比较SO2和I的还原性强弱,接下来的操作是____  

A.打开K1  B.打开K2 C.同时打开K1和K2

(5)若打开K2,通入Cl2恰好将Fe2+、I全部氧化后,再打开K1通入SO2,当Fe3+全部转化为Fe2+时,此时通入的SO2的体积(标准状况下)为____  

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答案(点此获取答案解析)

C,Na2SO3+H2SO4\u2550Na2SO4+SO2\u2191+H2O,\u6c22\u6c27\u5316\u94a0\u6eb6\u6db2,2I\ufe63+Cl2\u2550I2+2Cl\ufe63<\

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    People who do not get enough vitamin A in their diet may develop night blindness. But in the developing world, a lack of vitamin A causes much more serious harm to children. The world Health Organization links the lack of vitamin A to as many as 250,000 child deaths every year.

    One excellent source of vitamin A is found in newly developed sweet potatoes with orange flesh. Orange sweet potatoes contain high levels of beta-carotene, which the body changes into vitamin A. Experts say orange sweet potatoes could help the Africans who are lacking in vitamin A. But, first, more people will need to be persuaded to eat them. Sweet potatoes need a better image in Africa. Jan Low with the International Potato Center says, “We do have an image problem with sweet potatoes. In many African countries, they are seen as a crop of the poor.”

    Ms. Low explains that sweet potatoes are mainly grown by poor women to feed their families in case another crop fails. The sweet potatoes commonly grown in Africa have white or yellow flesh. But they are low in vitamin A.

    Jan Low took part in a project to study how to market orange sweet potatoes to Africans best. She worked on an information campaign(活动) in Mozambique and Uganda. The campaign included radio messages about the nutritional(营养的) benefits of the orange sweet potato. They advertised its ability to “fight diseases, make you strong, clear you skin and make you look healthy”. In areas without radio, the campaigners spread the message through theater. The performances included singing, dancing and storytelling. And everywhere they went, the campaigners wore orange T-shirts and hats. They even drove orange cars.

    Dan Gustafson heads the Washington office of the United Nations Food and Agriculture Organization. He mentions the efforts in the past to increase the popularity of other nutritious crops. He says most of these efforts failed because organizers of the campaigns did not consider what people wanted to eat. People want to eat what they are familiar with. But Mr. Gustafson sees a better chance for the efforts to increase the popularity of the orange sweet potato in Africa. Except for the color, the orange sweet potato is almost the same as what people already eat. Dan Gustafson says, “I think this time the campaigners will succeed, because they have made enough advertisements and the difference between the vegetable they have advertised and what people already eat is not a radical one.”