问题 实验题

小东在帮助老师整理实验室时,发现了一瓶NaOH溶液(如下图)可能变质了,于是小东开始了探究活动。 

(1)提出问题:

①上图所示试剂瓶口为什么有一层白色固体?请用化学方程式解释:__________________________。

②为了检验试剂瓶中的NaOH溶液是否变质,___________(选填“能” 或“不能”)用酚酞试液,理由是____________________________________________。

(2)探究NaOH溶液是否变质:

(3)为了证明变质的溶液中仍然存在NaOH,探究如下:

(4)通过上述实验探究,说明氢氧化钠溶液暴露在空气中容易变质,因此,氢氧化钠溶液应__________________保存。

答案

(1)①2NaOH+CO2==Na2CO3+H2

         ②不能;若NaOH溶液已变质,其所含Na2CO3也呈碱性

(2)

(3)

(4)密封

阅读理解

阅读理解。

     In the course of working my way through school, I took many jobs I would rather forget. But none of

these jobs was as dreadful as my job in an apple plant. The work was hard; the pay was poor; and, most of

all, the working conditions were terrible.

     First of all, the job made huge demands on my strength. For ten hours a night, I took boxes that rolled

down a metal track and piled them onto a truck. Each box contained twelve heavy bottles of apple juice. I

once figured out that I was lifting an average of twelve tons of apple juice every night.

     I would not have minded the difficulty of the work so much if the pay had not been so poor. I was paid

the lowest wage of that time-two dollars an hour. Because of the low pay, I felt eager to get as much as

possible. I usually worked twelve hours a night but did not take home much more than $ 100 a week.

     But even more than the low pay, what made me unhappy was the working conditions. During work I was

limited to two ten-minute breaks and an unpaid half hour for lunch. Most of my time was spent outside loading

trucks with those heavy boxes in near-zero-degree temperatures. The steel floors of the trucks were like ice,

which made my feet feel like stone. And after the production line shut down at night and most people left, I

had to spend two hours alone cleaning the floor.

     I stayed on the job for five months, all the while hating the difficulty of the work, the poor money, and the

conditions under which I worked. By the time I left, I was determined never to go back there again.

1. Why did the writer have to take many jobs at that time?

A. To pay for his schooling.

B. To save for his future.

C. To support his family

D. To gain some experience

2. The following facts describe the terrible working conditions of the plant EXCEPT ______.

A. loading boxes in the freezing cold

B. having limited time for breaks

C. working and studying at the same time

D. getting no pay for lunch time

3. What is the subject discussed in the text?

A. The writer's unhappy school life.

B. The writer's eagerness to earn money.

C. The writer's experience as a full-time worker.

D. The writer's hard work in an apple plant.

4. How is the text organized?

A. Topic-Argument-Explanation

B. Opinion-Discussion-Description

C. Main idea-Comparison-Supporting examples

D. Introduction-Supporting examples-Conclusion

单项选择题