硅是常温下化学性质稳定的半导体材料，广泛应用于计算机技术、光电池领域．某结晶硅厂用石英石（主要成分是SiO2）和焦炭为原料生产粗硅（主要成分是Si），反应在电炉中进行，其化学方程式为SiO2+2C
Si+2C0↑． 高温 .
（1）求25t含SiO296%的石英石中SiO2的质量．
（2）用25t含SiO296%的石英石，理论上可生产出含Si 80%的粗硅多少吨？
（1）25t含SiO296%的石英石中SiO2的质量25t×96%=24t．
（2）设理论上可生产出含Si80%的粗硅的质量为x
SiO2+2C
Si+2C0↑ 高温 .
60 28
24t 80%x
=60 28
x=14t24t 80%x
答：（1）25t含SiO296%的石英石中SiO2的质量为24t；（2）理论上可生产出含Si80%的粗硅的质量为14t．
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Last night I was driving from Harrisburg to Lewis burg, a 1 of about eighty miles. It was late and I was in a hurry. However, if anyone asked me how fa  st I was 2 , I'd say I was not overspeeding. Several times I got 3 behind a slow-moving truck on a narrow road, and I wa  sholding my fists tightly with 4 . At one point along an open highway, I 5 a crossroads with a traffic light. I was alone on the road by now, but as I 6 the light, it turned red and I braked to a stop. I looked left, right and behind me. Nothing. No cars, no s  uggestion of headlights, but there I sat, waiting for the light to 7 , the only human being for at least a mile in any 8 .I started 9 why I refused to run the light. I was not afraid of being 10 , because there was obviously no policeman around, and there certainly would have been no 11 in going through it. Much later that night, after I 12 a group of friends in Lewisburg and climbed into bed near midnight, the question of why I'd stopped for that light 13 me. I think I stopped because it's part of a contract (合同) we all have with each other. It is not only the 14 , but also it  is an arrangement we have, andwe  trust each other to 15 it: we don't go through red lights. Like most of us, I am more likely to be16 from doing something bad by the social convention(传统习惯) that 17 it than by any law against it. It's amazing that we ever 18 each other to do the right thing, isn't it? And we do, too. Trust is our 19 preference. I was so 20 of myself for stopping for the red light that night. | ||||
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