问题 实验题

(11分)某兴趣小组在网上收集到如下信息:钾、钙、钠、镁等活泼金属都能在CO2气体中燃烧。他们对钠在CO2气体中燃烧后生成的白色物质进行了如下探究:

[实验]将燃烧的钠迅速伸入到盛有装满CO2的集气瓶中,钠在其中继续燃烧至完全,反应后冷却,瓶底附着黑色颗粒,瓶壁上粘附着白色物质。

(1)通过钠在CO2气体中燃烧的实验,你认为物质燃烧的条件是              

(2)实验室不小心发生钠着火,下列灭火方法正确的是          

A.用水扑灭

B.用泡沫灭火器扑灭

C.用干粉灭火器扑灭

D.用砂子扑灭[提出假设]

假设1:白色物质是Na2O。

假设2:白色物质是Na2CO3

假设3:白色物质是Na2O和Na2CO3的混合物。

[设计实验方案.验证假设]该小组对燃烧后生成的白色物质进行如下探究:

实验方案实验操作实验现象结论
方案1取少量白色物质于试管中,加入适量水,振荡,样品全部溶于水,向其中加入无色酚酞试液溶液变成红色白色物质为Na2O
方案2① 取少量白色物质于试管中,加入适量水,振荡,样品全部溶于水,向其中加入过量的BaCl2溶液出现白色沉淀 
② 静置片刻,取上层清液于试管中,滴加无色酚酞试液无明显现象
[思考与交流]

(3)甲同学认为方案1得到的结论不正确,其理由是                 

(4)乙同学认为方案2得到的结论正确,白色物质为               。理由是                    

(5)写出钠在二氧化碳中燃烧的化学方程式为                

(6)丙同学认为白色物质有可能是氢氧化钠。你是否同意丙同学的观点,并简述理由:                            

答案

(2)D (1分)

(3)Na2CO3溶液显碱性,也会使酚酞变红(1分)

(4)Na2CO3(1分)方案2的①中出现的白色沉淀是BaCO3,所以燃烧后的白色物质中有Na2CO3,②中滴加无色酚酞试液无明显现象,说明燃烧后的白色产物中没有Na2O。(2分)

(5)4Na+3CO2====2Na2CO3+C(2分)

(6)不同意。因为反应物中无氢元素(或违背质量守恒定律)(2分)

单项选择题
阅读理解

阅读理解。

     After giving a talk at a high school, I was asked to pay a visit to a special student. An illness had kept

the boy home, but he had expressed an interest in meeting me. I was told it would mean a great deal to

him, so I agreed.

     During the nine-mile drive to his home, I found out something about Matthew. He had muscular

dystrophy  (肌肉萎缩症). When he was born, the doctor told his parents that he would not live to five,

and then they were told he would not make it to ten. Now he was thirteen. He wanted to meet me

because I was a gold-medal power lifter, and I knew about overcoming obstacles and going for my

dreams.

     I spent over an hour talking to Matthew. Never once did he complain or ask, "Why me?" He spoke

about winning and succeeding and going for his dreams. Obviously, he knew what he was talking about.

He didn't mention that his classmates had made fun of him because he was different. He just talked about

his hopes for the future, and how one day he wanted to lift weights with me. When we had finished talking, I went to my briefcase and pulled out the first gold medal I had won and put it around his neck. I told him

he was more of a winner and knew more about success and overcoming obstacles than I ever would. He

looked at it for a moment, then took it off and handed it back to me. He said, "You are a champion. You

earned that medal. Someday when I get to the Olympics and win my own medal, I will show it to you."

     Last summer I received a letter from Matthew's parents telling me that Matthew had passed away.

They wanted me to have a letter he had written to me a few days before:

Dear Dick,

     My mum said I should send you a thank-you letter for the picture you sent me. I also want to

let you know that the doctors tell me that I don't have long to live any more, but I still smile as

much as I can.

     I told you someday that I would go to the Olympics and win a gold medal, but I know now I

will never get to do that. However, I know I'm a champion, and God knows that too. When I get

to Heaven, God will give me my medal and when you get there, I will show it to you. Thank you

for loving me.

                                                                                                                      Your friend,

                                                                                                                        Matthew

1. The boy looked forward to meeting the author because _________.  

A. he was also good at weight lifting    

B. he wanted to get to the Olympics and win a medal  

C. he was one of the author's students    

D. he admired the author very much

2. From the passage we learn that _________.  

A. Matthew was an athlete                              

B. Matthew was an optimistic and determined boy  

C. The author used to have the same disease as Matthew had  

D. Matthew became a champion before he died

3. Matthew didn't accept the author's medal because _________.

A. he thought it was too expensive                        

B. he was sure that he could win one in the future

C. he thought it was of no use to him as he would die soon    

D. he would not be pitied by others

4. What would be the best title for this passage?  

A. A sick boy.                          

B. A special friend.      

C. A real champion.                      

D. A famous athlete.