将20克甲、5克乙、8克丙三种纯净物混合，在密闭容器中加热发生化_爱下问搜题

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问题选择题

将20克甲、5克乙、8克丙三种纯净物混合，在密闭容器中加热发生化学反应，

经分析可知：反应后混合物中含有5克甲、16克丙，还含有一种新物质丁。则丁物质的质

量是

A．12g

B．9g

C．4g　　

D．17g

答案

答案：A

分析：根据质量守恒定律，必须为参加化学反应前各物质的质量总和等于反应后生成各物质的质量总和；所以参加反应的B的质量可依据质量守恒定律来计算；则根据质量守恒定律，可求丁的质量．

解：方法一：因为“将20克甲、5克乙、8克丙三种纯净物混合，在密闭容器中加热发生化学反应，经分析可知：反应后混合物中含有5克甲、16克丙，还含有一种新物质丁”，则：甲的质量减少15克、乙的质量减少5克，二者为反应物；丙的质量增加8克，丁质量也增加，则二者为生成物，故根据质量守恒定律，可求丁的质量为：15+5-8=12克．

方法二：根据质量守恒定律，20克甲、5克乙、8克丙的总质量，等于反应后混合物中5克甲、16克丙，新物质丁的总质量．则丁物质的质量为20+5+8-（5+16）=12克．

故选A．

点评：此题是质量守恒定律以及反应类型考查题，解题的关键是确定甲、乙、丙的质量，求丁的质量以及掌握反应类型的含义．

填空题

如脱轨车轮距钢轨外侧不足240mm时，即可安放（）起复。

完形填空

I live in Hollywood. You may think people in such an attractive, fun-filled place are _________ than others. If so, you have some ________ ideas about the nature of happiness.
　　Many intelligent people still equate(同等看待) happiness with ________. The _______ is that fun and happiness have ______ or nothing in common. Fun is what we experience during an act. Happiness is ________ we experience after an act. It is a deeper, more lasting emotion.
Going to an amusement park or ball game, watching a movie or television, are fun ______ that help us relax, ________ forget our problems and maybe even ________. But they do not bring happiness, because their _______ effects end when the fun ______.
I have often thought that ______ Hollywood stars have a role to ________, it is to teach us that happiness has nothing to do with fun. These rich, beautiful individuals have constant _________ to glamorous parties, fancy cars, expensive homes, everything that spells “happiness”.
But celebrities reveal(揭露) the ________hidden beneath all their fun: depression, alcoholism, drug addiction, broken marriages, troubled children and profound loneliness.
The way people stick to the _______ that a fun-filled, pain-free life equates happiness actually _____ their chances of ever obtaining real happiness. If fun and pleasure are equated with happiness, then pain ______ be equated with unhappiness. But, _______, the opposite is true: More times than not, things that lead to happiness _______ some pain.
As a result, many people avoid the very efforts that are the source of true happiness. They fear the pain inevitably brought by such things as marriage, raising children, professional achievement, religious commitment, civic or charitable work, and self-improvement.

B．temporarily

C．consequently

B．participation

B．unhappiness

C．presentation

D．disagreement

B．as a result