问题 填空题

某无色溶液,其中有可能存在的离子如下:Na+、Ag+、Ba2+、Al3+、AlO2-、S2-、CO32-、SO32- 、SO42-。现取该溶液进行有关实验,实验结果如下图所示:

(1)沉淀甲是        ,生成沉淀的离子方程式                  。

(2)沉淀乙是        ,由溶液甲生成沉淀乙的离子方程式                。

(3)沉淀丙是                      。

(4)综合上述信息,可以肯定存在的离子有                   。

答案

(1)S;  2S2-+SO32+6H+=3S↓+3H2O

(2)Al(OH)3; Al3++3HCO=Al(OH)3↓+3CO2

(3)BaCO3, 可能有BaSO4;    在沉淀丙中加入足量盐酸,若沉淀不能全部溶解,说明除BaCO3外还有BaSO4;若全部溶解,则仅有BaCO3.

(4) S2-、SO、AlO、Na+

本题的突破口是沉淀甲、乙、丙的成分,加入过量的氢溴酸生成淡黄色沉淀甲,回顾中学化学中常见的淡黄色物质有AgBr、S、Ag3PO4等。这里应该排除排除Ag3PO4的,关键甲是AgBr还是S?若是AgBr沉淀的话,由于Ag+与题干中的4种阴离子均不能大量共存,从而否决了Ag+。可知甲是S,显然此处的S是溶液中S2-和SO32-在酸性条件下发生的归中反应生成的。由此推出原溶液中存在S2-和SO32-。由于有SO32-,所以一定不存在Ba2+、Fe3+。根据电中性原则,溶液中必须有阳离子,故一定存在Na+。气体甲可能是HBr与过量的S2-反应生成的H2S,也可能是HBr与过量的SO32-反应生成的SO2,也可能是HBr与原溶液中可能存在的CO32-反应生成的CO2。过量的NH4HCO3中和多余的H+后,又反应生成白色沉淀乙,对照题干中的离子(Ag+、Ba2+、Fe3+都不存在),推出沉淀乙只可能是Al元素引起的Al(OH)3沉淀,即HCO3-与Al3+发生双水解所造成的,而Al3+来自于AlO2-与过量的氢溴酸反应生成的,所以原溶液中一定存在AlO2-。气体乙是HCO3-与剩余的H+以及Al3+反应产生的,只能是CO2。Ba(OH)2与上步过量的NH4HCO3反应,生成白色沉淀丙,即BaCO3沉淀,另外,也可能存在BaSO4沉淀,但无法确定原溶液中是否含有CO32-和SO42-。气体丙一定是NH4+与过量的Ba(OH)2反应生成的NH3

综上所述,肯定存在的离子有:Na+、AlO2-、S2-、SO32-;一定不存在的离子有:Ag+、Ba2+、Fe3+;可能存在的离子有:CO32-、SO42-

阅读理解

阅读理解。

 

     Welcome to your favorite show-"Music Land "! This month we are going to have some special

shows on Bach, the Father of Music.

     Johann Sebastian Bach was born in Germany (德国) in 1685, During his life, Bach wrote a lot of

music for the church (教堂) and for his students, but he himself did not keep his own works (作品)

carefully.  Luckily, his second wife (妻子) saved them for him, so today we can still remember Bach

through his music.

     Bach married twice in his life and had 20 children. He loved his family very much. He wrote music

for one of his daughters to tell her that too much coffee was bad for her health. I am now going to play

a song for you from this interesting Coffee Cantata. And we will hear more about Bach after this song.

1. Where was Bach born?        

A. Germany.              

B. America.         

C. Japan.                 

D. France.

2. Why is Bach's second wife important to his music?         

A. She helped Bach keep his works.         

B. Many of Bach's works were for her.         

C. She gave Bach a lot of good ideas about music.         

D. Her money helped Bach write music.

3. Why did Bach write the Coffee Cantata ?        

A. To celebrate his birthday.         

B. To show people his love of coffee.         

C. To tell his child not to drink so much coffee.        

D. To make a new kind of music for the church.

4. This passage may be a ____.        

A. fashion show          

B. radio show         

C. TV play                

D. talk show

5. What  is this  passage mainly (主要地) about?        

A. Ways to learn Bach's music.          

B. The Bach family's history.          

C. Bach's great church music.          

D. Stories about Bach and his music.

问答题