问题 问答题

某研究性学习小组同学设计了如图制取氯气并验证其性质的实验装置.

请回答下列问题:

(1)该实验中A部分的装置是______(填写装置的序号)

(2)A中发生反应一段时间后,B中的现象是______;整套实验装置存在的明显缺陷是______.

(3)写出D装置中发生反应的离子方程式:______.

(4)请你帮该小组同学设计一个实验,证明洗气瓶C中的Na2SO3已被氧化(简述实验步骤):______.

答案

(1)该反应的反应物是固体和液体,反应条件是加热,所以应选固液混合加热型装置.

故选丁.

(2)氯气有氧化性,能和碘化钾反应生成碘单质和氯化钾Cl2+2KI=2KCl+I2,碘遇淀粉变蓝色.氯化氢有刺激性气味,尾气不能直接排空,要用尾气处理装置进行处理,所以该装置没有尾气处理装置.

故答案为:溶液变蓝色;无尾气处理装置.

(3)氯气和水反应生成盐酸和次氯酸Cl2+H2O?H++Cl-+HClO,盐酸是强酸,能和碳酸氢根离子反应生成二氧化碳和水HCO3-+H+=H2O+CO2↑.

故答案为:Cl2+H2O?H++Cl-+HClO,HCO3-+H+=H2O+CO2↑.

(4)氯气有强氧化性,亚硫酸根离子有还原性,所以氯气和亚硫酸根离子能发生氧化还原反应生成硫酸根离子、氯离子和氢离子Cl2+SO32-+H2O=SO42-+2Cl-+2H+;如果亚硫酸钠被氧化,会生成硫酸钠,硫酸钠和氯化钡能发生 反应生成白色沉淀硫酸钡,亚硫酸钡也是沉淀,所以要先排除亚硫酸盐的干扰,再用氯化钡检验硫酸根离子,检验方法为取少量反应后的溶液于试管中,加入HCl溶液至不再产生气体为止,再滴加BaCl2溶液,如果有白色沉淀生成,证明Na2SO3已被氧化.

故答案为:取少量反应后的溶液于试管中,加入HCl溶液至不再产生气体为止,再滴加BaCl2溶液,如果有白色沉淀生成,证明Na2SO3已被氧化.

阅读理解

阅读理解。

     A blind boy sat on the steps of a building with a hat by his feet. He held up a sign which said, "I am

blind, please help."

     There were only a few coins in the hat. A man was walking by. He took a few coins from his pocket

and dropped them into the hat. He then took the sign, turned it around, and wrote some words. He put

the sign back so that everyone who walked by would see the new words.

Soon the hat began to fill up. A lot more people were giving money to the blind boy. That afternoon the

man who had changed the sign came to see how things were. The boy heard his footsteps and asked,

"Were you the one who changed my sign this morning? What did you write?"

     The man said, "I only wrote the truth. I said what you said but in a different way."

     What he had written was, " Today is a beautiful day but I cannot see it." Do you think the first sign

and the second sign were saying the same thing?

     Of course, both signs told people the boy was blind. But the first sign simply told people to help by

putting some money in the hat. The second sign told people that they were able to enjoy the beauty of

the day, but the boy could not enjoy it because he was blind.

     The first sign simply said the boy was blind. The second sign told people they were so lucky that they

were not blind.

1. A blind boy sat on the steps of a building in order to______.    

A. wait for some people                    

B. get money from others

C. make the writer help him              

D. hold up a sign

2.The man ______when he saw the blind boy.    

A. took away the blind boy's money              

B. gave the boy a new hat

C. brought the boy a sign                      

D. gave the boy some money and wrote some words on the sign

3. What happened to the blind boy after the man wrote the words on the sign?    

A. The boy was taken away by the police

B. Nobody gave the blind boy money any more

C. More people dropped money into the boy's hat

D. The blind boy could see the beautiful day

4. What do you think of the sign written by the man?

A. It has the different meaning to the first sign

B. It has the same meaning to the first sign and is expressed in another better way.

C. The man's sign tells people it is a beautiful day

D. People know the boy is blind after reading the man's sign

5. What can we learn from this passage?

A. It's helpful of us to help people in need

B. There are many poor people in the world like the blind boy

C. It's a good way to make money by holding a sign

D. We should learn to speak to others in a suitable way

单项选择题