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问题 实验题

为了探究SO2与Na2O2的反应是否类似于CO2，甲同学设计了如图实验装置。

回答下列问题：

（1）制取SO2的合适试剂是               。

a．80%的H2SO4(aq)     b．10%的H2SO4(aq) 

c．Na2SO3(s)           d．Na2SO3（aq） 

（1）装置C中NaOH(aq)的作用是                                                           。

（1）移开棉花，将带火星的木条放在C试管口，未见木条复燃。甲同学因此认为SO2与Na2O2的反应不同于CO2。请按甲同学的观点写出反应的化学方程式                                      。

（1）检验反应后B装置中生成物的方法是                                                     。

（1）乙同学认为无论反应原理如何，最终都有O2产生。乙同学的理由是                       。按照乙同学的观点，该装置还需作如下改进：                                                。（简要阐述，并指明必需的装置名称与试剂。）

答案

（1）a、c（1分×2）    

（2） 吸收多余的SO2，防止污染环境（1分×2）

（3）SO2+ Na2O2→ Na2SO4（2分）

（4）取少量B中固体于试管中，加盐酸至溶液呈酸性，再滴入氯化钡溶液，若有白色沉淀生成，则B中反应后的生成物里有Na2SO4（2分）

（5）A中生成的SO2气体中含有水蒸气（2分）。在A和B之间连接一个装有浓硫酸的洗气瓶（或其他合适的干燥装置）。合理给分。     （2分）

题目分析：（1）因SO2的溶解度较大，应选用浓度较大的H2SO4溶液；为了使反应顺利进行须选择Na2SO3固体与硫酸反应（CaSO3固体与硫酸反应生成的硫酸钙微溶于水）．故答案为：bc（2）SO2有毒，直接排放到空气中污染环境．故答案为：吸收多余的SO2，防止污染环境（3）进入B装置的气体应该干燥，故应将②加在A和B之间．故答案为：②；将②加在A和B之间（4）木条不复燃，说明没有氧气生成，Na2O2有强氧化性，有SO2较强的还原性，产物应为Na2SO4，方程式为：SO2+Na2O2=Na2SO4．故答案为：SO2+Na2O2=Na2SO4

（5）在检验是否有Na2SO4生成时，要考虑到Na2SO3的干扰，因为SO32-有较强的还原性，可被过氧化钠氧化成SO42-．故答案为：不合理；如果固体中还有未反应的Na2O2，也能氧化亚硫酸钠为硫酸钠．（6）将Na2SO4转化成BaSO4沉淀，通过称量BaSO4沉淀的质量，计算含量，故应为acd。故答案为：acd

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单项选择题

We once had a poster competition in our fifth grade art class.

"You could win prizes," our teacher told us as she wrote the poster information on the blackboard. She passed out sheets of construction paper while continuing. "The first prize is ten dollars. You just have to make sure that the words on the blackboard appear somewhere on your poster. "

We studied the board critically. Some of us looked with one eye and held up certain colors against the blackboard rocking the sheets to the right or left while we conjured up our designs. Others twisted their hair around their fingers or chewed their erasers while deep in thought. We had plans for that ten-dollar grand prize, each and every one of us. I’m going to spend mine on candies one hopeful would announce while another practiced looking serious wise and rich.

Everyone in the class made a poster. Some of us used parts of those fancy paper napkins, while others used nothing but colored construction paper. Some of us used big designs and some of us preferred to gather our art tidily down in one comer of our poster and let the space draw the viewer’s attention to it. Some of us would wander past the good students’ desks and then return to our own projects with a growing sense of hopelessness. It was yet another grown up trick of the sort they seemed especially fond of making all of us believe we had a fair chance and then always—always—rewarding the same old winners.

I believe I drew a sailboat, but I can’t say that with any certainty. I made it. I admired it. I determined it to be the very best of all of the posters I had seen and then I turned it in.

Minutes passed.

No one came along to give me the grand prize and then someone distracted me and I probably never would have thought about that poster again.

I was still sitting at my desk thinking, what poster When the teacher gave me an envelope with a ten-dollar bill in it and everyone in the class applauded for me.

What was the teacher’s requirement for the poster（）

A．It must appear in time.

B．It must be done in class.

C．It must be done on a construction sheet.

D．It must include the words on the blackboard.
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