题干

化学是以实验为基础的学科,化学实验设计和操作中必须十分重视安全问题和环境保护问题.下列操作不是围绕上述问题的是(   )

A:用氯酸钾和二氧化锰制氧气时用排水法收集后,应从水中撤出导管后再停业加热

B:在氢气还原氧化铜停止加热后,还要继续通一会儿氢气

C:实验室制备CO气体必须在通风橱中进行

D:蒸馏操作时应在混合液中加入沸石

上一题 下一题 0.0难度 选择题 更新时间:2017-06-20 07:23:18

答案(点此获取答案解析)

B

同类题5

阅读下面短文,掌握其大意,然后从下面各题所给的四个选项(A、B、C、D)中,选出可以填入空白处的最佳选项。

    I learned all about taking responsibility from my mother's tough love. My mom had a wonderful way of helping you1up and realize that your life is going to be what you make it.

    She had this circular way of2you took responsibility for your decisions and the person you would3She would say, “It's your45,“What you want and what you get are sometimes two6different things.” And then, “No one ever said life was fair.” And she would7these comments together in such a way that you could never8an argument, and yet, the9was that you realized your life is going to be what you make it.

    So I might go to my mom and say, “I'd like to10football”. And she would say, “Well, it's your life. If you want to go out there and get11and hurt and break your knees and limp around the rest of your life, that's fine.” That is12I would say, “Well, you know, that won't13I'm really fast.” And she would reply, “Well, we don't really have the money.” And then I would14, “Yes but that's not fair.” And she would reply, “Well, life isn't15” Then I would say, “But I've been eager to." And she would reply, “Yes, but what you want and what you get are usually two entirely different things.”

    It was the combination of these16that allowed my mother to lead me down the right path under her17but let me feel as if I was making the decisions18my own. The sum total of that19was, in the end, you're20for the life you lead. That's the best advice I've ever gotten.