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已知氢氧化钠必须密封保存，是因为 （用反应式表示）．现有13.3克已部分变质的固体NaOH，将该固体加入100克稀盐酸中，刚好完全反应，并产生2.2克二氧化碳．

求：（1）固体中变质的物质的质量

（2）反应后溶液中溶质的质量分数．

答案

氢氧化钠与空气中二氧化碳反应生成的碳酸钠和水，反应的方程式是：2NaOH+CO2=Na2CO3+H2O，固体中变质的物质是碳酸钠；

（1）设碳酸钠的质量为X，与盐酸反应生成的氯化钠的质量为Y

则   Na2CO3+2HCl=2NaCl+H2O+CO2↑

     106         117       44

     X            Y       2.2克

106
44
=
X
2.2克
   解得：X=5.3克

 

117
44
=
Y
2.2克
   解得：Y=5.85克

所以固体中碳酸钠的质量为5.3克，未变质的氢氧化钠的质量为：13.3克-5.3克=8克；

设8克的氢氧化钠与盐酸反应生成的氯化钠的质量是Z

则   NaOH+HCl=NaCl+H2O

     40       58.5

     8克      z

40
58.5
=
8克
Z
   解得：z=11.7克

（2）反应后溶液中溶质的质量分数是

5.85克+11.7克
13.3克+100克-2.2克
×100%=15.8%

答：（1）固体中变质的物质的质量是5.3克．

（2）反应后溶液中溶质的质量分数是15.8%．

单项选择题 A1型题

在治疗性环境中，工作人员应做到"四轻"（）

A.谈话轻、走路轻、操作轻、开门轻

B.说话轻、走路轻、动作轻、开门轻

C.说话轻、走路轻、操作轻、关门轻

D.谈话轻、走路轻、操作轻、开门轻

E.说话轻、走路轻、动作轻、关门轻
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阅读理解

第三部分：阅读理解 (共15小题；每小题2分，共30分)

阅读下列短文，从每题所给的四个选项（A、B、C和D）中，选出最佳选项，并在答题卡上将该项涂黑。

Who decides how English is spoken around the world? Do teachers in the colleges and schools? What about those who write dictionaries or books? Do they decide what is good and what is bad English? Or do governments decide when a language will change? Probably you have thought about this question once or twice before. The answer is that none of these people decide how English will be spoken. Believe it or not, many of the biggest changes in how English is spoken have come from common people in the streets. And one of the most important places where English has changed is on the playground! These playground can be any place where young people meet, such as a sports field or a beach. For example, black kids invented many new words in American English as they played basketball or music. Often words used by black kids in the big cities become popular with other kids many years later. Another popular sport, baseball, has also given many words and expressions to American English. On the beaches of southern California, teenagers invented words to describe how they felt when they surfed. These words found their way into the high schools and then to other places. Similar changes in English happened among young people in Ireland and Australia. Children from one group would find ways to play with children of another group more easily. Often they made new words just to develop an identity different from their parents.

56. Who decides how English is spoken?

A. Governments        B. Teachers       C. Ordinary people    D. Black kids

57. According to the passage many English words come from ______.

A. everyday life        B. textbooks       C. dictionaries        D. baseballs

58. Why do these kids invent new words?

A. because they want to make up a dictionary.

B. because they try to beat their teachers.    

C. because they are asked to do so.

D. because they want to feel different from their parents
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