问题 填空题

某同学称取9g淀粉溶于水,测定淀粉的水解率,其步骤如下

(1)各步所加试剂分别为A.________,B.________, C._________。

(2)___(填“可以”或“不可以”)只加A、C溶液而不加B溶液,原因是_______________________。

(3)当析出2.16 g单质银时,淀粉的水解率为_______。

答案

(1)稀H2SO4;NaOH溶液;银氨溶液

(2)不可以;醛基与银氨溶液的反应必须在碱性条件下进行

(3)18%

阅读理解

In the United States, it is not usual to telephone someone early in the morning. If you telephone early in the day, while he is shaving or having breakfast, the time of the call shows that the matter is very important and requires immediate(立即的) attention. So it is with the telephone calls made after 11:00 pm. If someone receives a call during sleeping hours, he may think that it’s a matter of life and death. The time chosen for the call communicates its importance.

In social life, time plays a very important part. In the USA guests are likely to feel they are not highly regarded if the invitation to a dinner party reaches them only three or four days before the party date. But it is not true in all countries. In other areas of the world, it may be thought silly to make an appointment(约会) too far ahead because plans which are made for a date more than a week away may be forgotten. The meaning of time is not the same in different cultures that treat time differently; being on time is valued highly in American life, for example. If people are not on time, they may be regarded as impolite or not fully responsible(责任). In the USA no one would think of keeping a business friend for an hour; it would be too impolite. A person who is 5 minutes late is asked to make a shout apology (道歉). If he is less than 5 minutes late, he will say a few words of explanation(解释), though perhaps he will not complete the sentence.

小题1:A call at midnight would mean_________.

A.the matter is less important

B.the matter is too difficult to handle

C.the matter requires immediate attention

D.it is a matter of life and death小题2:According to the passage, time plays a very important part in__________.

A.everyday life

B.personal life

C.getting along with others

D.business小题3:In the passage, the writer suggests that invitation cards should be sent___________.

A.three or four days before the party date in all cultures

B.three or four days before the party date in some cultures

C.three or four days before the party date in the USA

D.at your chosen time

选择题