下列有关实验及其现象描述不正确的是
A．红磷在氧气中燃烧产生大量白烟
B．铁在空气中燃烧火星四射，生成黑色固体
C．二氧化碳通入澄清石灰水中，石灰水变浑浊。
D．二氧化碳通入紫色的石蕊试液后溶液变成红色
答案：B
分析：根据已有的知识进行分析，红磷在氧气中燃烧能产生大量白烟，铁在氧气中燃烧火星四射，生成黑色固体，电解水时，负极产生氢气，正极产生氧气，二氧化碳能和水反应生成碳酸．
解：A、红磷在空气和氧气中都能燃烧，产生大量的白烟．
B、铁在空气中不能燃烧．
C、电解水时负极产生的是氢气，氢气燃烧产生淡蓝色火焰．
D、二氧化碳能与水反应生成碳酸，水溶液显酸性，能使紫色石蕊试液变红．
故选B．
点评：本题主要考查物质发生化学变化时的现象，完成此题，可以依据已有的知识进行．
The elderly Chinese man in the small booth (售票口) behind the thick glass shook his head. I didn't need to know a word of Chinese to understand there were beds available for the Thursday night train from Beijing to Shanghai. I had a Friday morning with my college friend. I must be on that train. Desperate times desperate measures. So I squatted(蹲下). I assumed that this was the international for “Are there any hard seats available?” , there were. It was seat 109. Very quickly, I found it. The Chinese man sitting in it, however, seemed to beg to differ. I panicked. I am a man who usually avoids conflicts(冲突) and so I my seat, as if still looking, to buy myself more time. I had two options: The first is to be a and ask for what was rightfully mine. The second was to 23 and spend the next 13 hours staying in a corner. Well, nine out of ten times I choose the second option. But at that moment, every square inch of had already been claimed. There wasn’t a corner in which to cower(退缩). So, I mustered up(聚集) some and presented the man with my proof of ownership. He looked at my ticket and . About midnight my became heavy and I was ready for the lights to dim and my date Ms ZZZZ to start. But the room bright and hot. I tried to persevere and was even able to work into a sleeping position. It is here I must admit: I have a bladder (膀胱). The man next to me drank a Coca-Cola, a bag of milk and a bottle of water and the course of 13 hours he did not move once. I drank but finally, I made my way to the bathroom at 3:02 am. After waiting in a thick cloud of cigarette smoke, I finally used the bathroom. The philosophy(原则) of my sleeping was right: if you get a seat on a train, don’t move.
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