问题 问答题

在我国青海湖地区有一种说法,冬天捞碱,夏天晒盐.这里的碱是指Na2CO3,盐是指NaCl.人们从盐湖中捞得的碱会含有少量的NaCl.某研究性学习小组称取含NaCl的Na2CO3,固体25.0g,将其配制成溶液,再向其中逐滴加入足量的溶质质量分数为7.3%的稀盐酸,使气体完全放出,共收集到8.8g二氧化碳气体.试计算:(1)原固体中Na2CO3,的质量分数;(2)反应中消耗的盐酸的总质量.

答案

(1)设碳酸钠的质量为x,盐酸溶液中溶质的质量为y.

     Na2CO3+2HCl=2NaCl+H2O+CO2

     106     73            44

      x      y            8.8g

      

106
44
=
x
8.8g

         x=21.2g

       

73
44
=
y
8.8g

         y=14.6g

    

21.2g
25g
×100%=84.8%

 答:原固体中碳酸钠的质量分数为84.8%.

(2)反应中消耗的盐酸的总质量为:

14.6g
7.3%
=200g 答:反应中消耗盐酸的总质量为200g.

阅读理解

阅读短文,选择正确答案。

      One day I happened to meet an Englishman in the street and soon we began to talk. As I was talking about

how I was studying English, the foreigner seemed to be very surprised, gently shaking his head and saying "You

don't say!" I was puzzled, and I thought, "Perhaps this is not a right thing to talk about." So I said to him. "Well,

shall we talk about the Great Wall? Have you ever been there?"

      "Certainly! Everyone at home will laugh at me if I leave here without seeing it. The Great Wall is wonderful!"

"Yes, it is one of the wonders in the world. And people of many countries have come to visit it." As I went on

more about it, he stopped me again, "You don't say!"

      I couldn't help asking, "Why do you ask me not to talk about it?"

      "Well, I don't ask you to do so," he answered, greatly surprised.

      "Didn't you say 'You don't say'?" I asked again.

      Hearing this, the foreigner laughed loudly. He began to explain, " 'You don't say!' means 'Really?'. Perhaps

you know little about English idioms (习语)."

      Wow! How foolish I was! Since then I began to learn more English idioms.

1. The writer was puzzled (疑惑) because _________. [ ]

A. the foreigner has some trouble in understanding him

B. the writer himself didn't understand the meaning of "You don't say!"

C. the foreigner was not polite

2. What made the foreigner laugh? [ ]

A. The English idiom.

B. The writer's talking about the Great Wall.

C. The writer's question.

3. The story probably happened in _______. [ ]

A. China

B. America

C. England

4. The writer was puzzled ______ in the passage. [ ]

A. once

B. twice

C. three times

5. The English idiom "You don't say!" means "________". [ ]

A. Really?

B. You're right.

C. Thank you.

单项选择题