A、B、C、D是初中化学课本中出现的各不相同的4种物质，它们都含

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问题问答题

A、B、C、D是初中化学课本中出现的各不相同的4种物质，它们都含有相同的一种元素，其中A是一种黑色粉末，它们之间的转化关系如图所示．请你分析，然后回答：

（1）用化学式表示：A：______；D：______；

（2）写出A→B的化学方程式：______，该反应属于______（填序号）．

①置换反应 ②化合反应 ③分解反应 ④复分解反应．

答案

A是一种黑色粉末，则A可能是碳，碳能燃烧生成二氧化碳，则B可能是二氧化碳，二氧化碳能与氢氧化钙反应生成碳酸钙沉淀，则C可能是碳酸钙，碳酸钙能与水和二氧化碳转化生成碳酸氢钙，碳酸氢钙能分解生成二氧化碳，代入框图，推断合理，

（1）A是碳，D是碳酸氢钙，故填：C，Ca（HCO₃）₂；

（2）碳能燃烧生成二氧化碳，该反应属于化合反应，故填：C+O₂

点燃

CO₂，②．

完形填空

Seven loyal（忠实的）readers came to the Teens Office two weeks ago. They had a wonderful day learning how to make a newspaper. But what 36 made them excited was that they had their say.
“What most _37_ me was when I was saying something, I found all eyes were on me,” said Tang Shining, one of the students. Her friend, Li Chunbei _38_, and felt very glad that when she was talking, the editors（编辑） nodded and _39_ took notes.
Students are happy to see the editors listen to their _40_. You may often _41_about being neglected（忽视） by teachers and parents. _42__ before complaining, please make sure that you have already spoken about your _43_.
Tra

ditionally in China, teachers at school and parents were_44_ the ones to tell teenagers what they should and shouldn’t do. The young are _45_ to doing what they are told, rather than thinking by themselves. But then their ideas would be locked in their brain and not be _46_.
A girl wrote to Teens about her family story. She _47__ to be very sad because her father seldom talked and played with her. After years of consideration, she _48_ decided to write her father a letter, telling him about her sadness. To her _49__, the father _50_, saying that he didn’t realize his mistake. From then on, he really _51_.
Sometimes, we need to let our _52__ be heard, so others can understand our thoughts and feelings.
Don’t be afraid of being _53_ for what you have done. You know it is your _54_ to speak your mind. Even if your suggestions are denied, at least you have tried your best. You will not be left with any _55_.

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