问题 选择题

实验室制浓硫酸、浓硝酸的混合物与苯反应制取硝基苯。得到粗产品后,要选用如下几步操作对粗产品进行精制:①蒸馏 ②水洗 ③用干燥剂进行干燥 ④用10%的NaOH溶液洗涤。正确的操作步骤是

A.①②③④②

B.②④②③①

C.④②③①②

D.③④①②③

答案

答案:B

题目分析:该反应中,最后制得的硝基苯中会有杂质苯、浓硫酸、和浓硝酸。

所以操作顺序如下:

第一步:浓硝酸和浓硫酸易溶于水而其它物质不易溶于水,所以先水洗洗去浓硝酸和浓硫酸;

第二步:用10%的NaOH溶液洗涤,进一步除去残留在苯和硝基苯中的酸;

第三步:第二步洗涤会残留部分氢氧化钠,氢氧化钠能溶于水而其他物质不溶于水,所以用水洗去多余的氢氧化钠;

第四步:用水洗涤后会残留部分水分,所以用干燥剂除去多余的水;

第五步:两者沸点不同,苯的沸点小,被蒸馏出,硝基苯留在母液中,所以采取蒸馏的方法分离硝基苯与苯。

所以B正确

点评:本题考查了提纯粗硝基苯的操作顺序,难度较大,首先要明确混合物中的成分,然后根据各物质的性质采取相应的方法去除杂质。

阅读理解

With the rapid social development, the Internet now provides social networks that include online movies and videos.The major television networks have much less control over your mind and their broadcasts for entertainment and, more importantly, advertising.It has long been known that television’s audience will spend more time on the Internet than watching TV.People have found another means of entertainment by going to websites which seem to satisfy their specific interests more completely.This isn’t very good news for the television networks.

The influence of people using DVRs (Digital Video Recorder) also has led to fewer and fewer viewers watching television commercials.Market research indicates the effectiveness of TV ads is getting weaker as a result.Many DVR owners are fast forwarding and skipping television commercials.With viewers now spending an average of four times longer on the Internet and more viewers avoiding commercials, this trend isn’t good for television’s advertising revenues(收益).

Major TV advertisers know full well that their advertising dollars on TV aren’t as an effective investment as they once were.The major players in advertising have been moving towards the Internet as a serious alternative means of advertising.

For thousands of people involved in Internet marketing, it’s history-making to share the revenue that previously all went to major television networks.There’s already a group of Internet marketers being paid a larger amount of advertising revenue.These are everyday people that work usually from home on their own.Advertisers can direct their advertising to websites where viewer types are more likely to be interested in their product or service.

The development of the Internet and its role and change in our lives cannot be compared to any other form of media created throughout the history of mankind.

小题1:People are going to websites for entertainment because _______.

A.they’d like to follow the last trend

B.there are fewer commercials

C.there are more movies and videos

D.they can choose what meets their particular needs小题2:We can learn from the second paragraph that ______.

A.viewers are bored with television commercials

B.the television viewing time should be limited

C.many television commercials are of poor quality

D.there are more commercials on DVRs than on TV小题3:It can be inferred from the passage that _____.

A.people spend time on the Internet mainly for entertainment

B.most people prefer to work at home nowadays

C.the Internet will attract more and more advertisers

D.the appearance of TV changed our lives小题4:The passage mainly tells us ________.

A.the rapid social development

B.the fast development of the Internet advertising

C.the way to advertise on the Internet

D.the influence of television commercials

单项选择题