问题 选择题

在氧化还原反应3S+6KOH=K2SO3+2K2S+3H2O中,被氧化与被还原的硫原子数之比为(  )

A.1:1

B.2:1

C.1:2

D.3:2

答案

在反应3S+6KOH=2K2S+K2SO3+3H2O中,只有S元素的化合价发生变化,氧化剂和氧化剂都是S,

反应中S→K2S,S化合价降低,则S被还原,S为氧化剂,

S→K2SO3,S化合价升高,则S被氧化,S为还原剂,

由生成物可知,被氧化与被还原的硫原子数之比为1:2.

故选C.

选择题
阅读理解

阅读理解。

    Christian Eijkman, a Dutch doctor, left the Netherlands for the island of Java. Many

people on the island had a disease called beri-beri. He was going there to try and find

a cure.

    At first, Eijkman thought some kind of germ (细菌) caused beri-beri. He raised some

chickens. He didn't eat them, but made experiments on them. The local people were quite

surprised at that. One day he noticed that his chickens became sick when they were fed

the food most Javanese ate-refined white rice (精炼米). When he fed them with unrefined

rice, also known as brown rice, they recovered. Eijkman realized that he had made an

important discovery - that some things in food could prevent disease. These things were

named vitamins (维生素). The Javanese were not getting enough vitamins because they had

actually removed the part that contains vitamins. Later, other diseases were also found

to be caused by the lack of vitamins in a person's food.

    Today many people know the importance of vitamins and they make sure they have enough

vitamins from the food they eat. If they don't, they can also take vitamin pills.

1. The underlined word "cure" in Paragragh 1 probably means ______. [ ]

A. a medical treatment

B. a kind of vitamin

C. a kind of germ

D. a kind of rice

2. Christian Eijkman went to the island of Java to ______.[ ]

A. spend his holiday

B. find ways to grow better crops

C. do some research about the island

D. help the Javanese with their illness

3. Why did Christian Eijkman raise some chickens? [ ]

A. To eat them.

B. To carry out his experiments.

C. To give the Javanese a surprise.

D. To make money by selling them.

4. We can learn from the passage that ______. [ ]

A. beri-beri was caused by chickens

B. the Javanese didn't like vitamins

C. Christian Eijkman's experiment was successful

D. the Javanese's disease was caused by a kind of germ