题干

正丁醛可在羰基钴催化下由丙烯氢甲酰化获得:CH3CH=CH2+CO+H2CH3CH2CH2CHO(正丁醛)副反应:CH3CH=CH2+CO+H2(CH32CHCHO(异丁醛),温度对丙烯氢甲酰化产物中正/异醛比的影响如下图:

下列说法正确的是                                           (   )

A:丙烯氢甲酰化反应是放热反应

B:丙烯与CO4H2混合催化时,可能有丙烷及正丁醇等副产物生成

C:相同物质的量的丙烯合成正丁醛时,温度越高,所获得的正丁醛的产量一定越大

D:温度不变时,只改变体系的压强,对产率没有影响

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答案(点此获取答案解析)

B

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    What are American high schools like? Well, I'm happy to tell you what I know.

    When I started school here, it had already been a week since the school opened. At this school, freshmen usually go on a trip for about three days at the beginning of school. Unfortunately I missed that wonderful trip, which would have been the best time to get to know my classmates. I was really sad. I wished I'd known about it earlier.

    Despite the disappointment, however, I gradually adapted to my new life and school.

    There is a space in the basement of the teaching building where students chat and meet each other. As we do not always have the same classrooms and classmates, the school wants us to get to know each other there. Students usually come to school early, sit in that space and have fun. Around the space, there are many lockers for students to leave their books in, so that students do not have to carry a heavy schoolbag everywhere.

    It really surprises me that we have almost no textbooks. We only have textbooks for World History and Algebra 2 and they are big and heavy, like bricks. For other classes, we only need binders (活页夹) with paper in them. Without textbooks, students learn things freely and actively. For example, my humanities teacher just teaches us what is in her mind at the time. We never know what we will learn.

    Another difference between American schools and Chinese schools is that American schools care about students' morality more than their academic studies. For example, if you do not finish your homework, you will just be asked to do it later, but if you cheat or lie, you will get a warning or even be kicked out.

    I think that most students here are good at schoolwork as well, but compared to Chinese students, they can make learning a more joyful experience. I think we should take the good points from our two different kinds of education to perfect our approach to studying.