题干

实验室制备硝基苯的主要步骤如下:

a.配制一定比例的浓H2SO4与浓HNO3的混合酸,加入反应器中;

b.向室温下的混合酸中逐滴加入一定量的苯,充分振荡,混合均匀;

c.在55℃~60℃下发生反应,直至反应结束;

d.除去混合酸后,粗产品依次用蒸馏水和5% NaOH溶液洗涤,最后再用蒸馏水洗涤;

e.将用无水CaCl2干燥后的粗硝基苯进行蒸馏,得到纯净硝基苯.

请填写下列空白:

①配制一定比例的浓H2SO4和浓HNO3的混合酸时,操作的注意事项是:____.

②步骤d中洗涤、分离粗硝基苯应使用的仪器是____.

③步骤d中粗产品用5% NaOH溶液洗涤的目的是____.

④制备硝基苯的化学方程式____.

上一题 下一题 0.0难度 选择题 更新时间:2018-03-11 10:32:19

答案(点此获取答案解析)

\u5148\u5c06\u6d53\u785d\u9178\u6ce8\u5165\u5bb9\u5668\u4e2d\uff0c\u518d\u6162\u6162\u6ce8\u5165\u6d53\u786b\u9178\uff0c\u5e76\u53ca\u65f6\u6405\u62cc\u548c\u51b7\u5374,\u5206\u6db2\u6f0f\u6597,\u9664\u53bb\u7c97\u4ea7\u54c1\u4e2d\u6b8b\u7559\u7684\

同类题3

阅读理解

    A culture's values can be mirrored by its humor. Humor has been evaluated by many great minds such as Thomas Hobbes, who, In"On Nature", disliked humor," Laughter is nothing else but sudden glory arising from sudden thought of feeling far better than others." He thought humor to be a negative quality of human narrow-mindedness.

    However, Mordechai Gordon, PhD of Education, insists," Humor allows us to view the world from an angle that is amusing rather than serious." I agree with Gordon. Learning to look at the world through humor is important.

    In the United States, every four years an election occurs. Without humor as a way to express their feelings, how would Americans be willing to support the election? Television shows like "The Daily Show" have become important parts of American culture. They are mothering the masses by unconsciously inputting politics into our mouths. They make politics fun.

    Of course, politics is only one type of humor. Social humor helps people through the twists and turns of the human condition. American pop culture promotes an unhealthy self image. On the topic of self-image, Hari Kondabolu stands out. He has a joke about the popular musical group "The Pussycat Dolls", describing their hit song "Don't Cha" as a negative representation of women. He points out an obvious offence in American culture.

    A study from Loyola University of Maryland has shown that humor is one determining factor for selecting a mating partner. Amongst other things, mates look for an outstanding funny bone in a potential partner.

    Of course, humor is not always used for good purposes. Humor can be linked to vulgarity(粗俗)and racism, but, like everything else, it has potential to unite human beings by allowing us to laugh at ourselves, our failures and our connection with one another.

    Though life may seem tough and depressing at times, all I have to do is look in the mirror at my increased wrinkles(皱纹)to know that there is a comedy out there that even Chaplin wasn't aware of.

    With that in mind, remember to laugh with humanity and sometimes at humanity.

根据短文内容,选择最佳答案,并将选定答案的字母标号填在题前括号内。