问题 单项选择题 A1/A2型题

用4-氨基安替比林分光光度法测定水中酚,经蒸馏后取蒸馏液进行测定,加试剂的顺序十分重要不能随意改变,否则测定失败。正确的顺序是()。

A.4-氨基安替比林→铁氰化钾→缓冲液

B.缓冲液→4-氨基安替比林→铁氰化钾

C.缓冲液→铁氰化钾→4-氨基安替比林

D.铁氰化钾→4-氨基安替比林→缓冲液

E.铁氰化钾→缓冲液→4-氨基安替比林

答案

参考答案:B

解析:用4-氨基安替比林分光光度法测定水中酚,加试剂的顺序不能改变,酚与4氨基安替比林反应分三步进行:①加入缓冲液,使溶液呈碱性,阻止4-氨基安替比林分解;②加入4-氨基安替比林与酚缩合;③加入铁氰化钾氧化剂形成醌式结构的红色染料。

阅读理解

阅读理解。

     From the earliest times, man has been interested in art. People have often worked together to collect and

save the world's art treasures.

     Fine art treasures from many countries are kept in an art museum called the Louvre in Paris, France. The

works of art have been collected by the people of France over many centuries. The Louvre has not always

been a museum. The first building was a fort (炮台). In 1190, it was the king's castle with high walls and a

round tower. It had a moat to prevent his enemies from walking in.

     Over the years, the number of buildings around the castle grew. By 1350, the castle was no longer needed

as a fort. The Louvre became a palace home for French kings and queens.

     During times of peace, new treasures were brought in. During days of war, many treasures were stolen,

and the buildings were damaged.

     When Francis I became king of France in 1515, he brought in artists from many countries. One of the

artists was Leonardo da Vinci from Italy. Da Vinci's "Mona Lisa" is the best known painting in the museum

today.

     In 1793, the Louvre became a public museum, just as it is now. It is a place where art treasures have been

saved for everyone to enjoy.

1. On the whole,this passage is mainly about _____.[ ]

A. an art museum called the Louvre 

B. an Italian artist named Leonardo da Vinci 

C. a king of France named Francis I 

D. the best known painting in Louvre

2. Why is it good for great art to be kept in public museums? [ ]

A. It helps people remember who the King of France is. 

B. It keeps people out of the palaces. 

C. It gives everyone a chance to enjoy good art. 

D. It helps people to know who is the greatest artist.

3. From the passage we know that _____. [ ]

A. it is not possible for treasures to be stolen 

B. old forts always make the best museums 

C. great art should be shared with all the people 

D. king Francis I of France brought in artists from an old fort

4. In the third paragraph the word "moat" probably means _____. [ ]

A. a high tower built in former times where soldiers watched out for enemies 

B. a long and deep ditch (沟) dug round a castle and was usually filled with water 

C. a cart pulled by horses on which soldiers fought 

D. a long and high wall around castle

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