题干

一般不用K、Ca、Na等活泼金属来置换盐溶液中的其他金属元素,这是教科书上的一句话.小科对此进行了思考,并查阅资料,对金属钠和硫酸铜溶液的反应进行探究.

【查阅资料】钠常温下就能与水发生剧烈反应,反应方程式为:2Na+2H2O═2NaOH+H2

【提出猜想】猜想一:金属钠和硫酸铜溶液反应会有铜生成.

猜想二:金属钠和硫酸铜溶液反应,生成的沉淀只有氢氧化铜.

【实验及现象】切取不同大小的钠块分别投入到两种不同浓度的硫酸铜溶液中,有关产生沉淀的现象如表所示

实验编号

钠块大小

硫酸铜溶液

实验中产生沉淀的现象

绿豆大小

稀溶液10mL

产生蓝绿色沉淀

绿豆大小

浓溶液10mL

产生蓝色絮状沉淀

豌豆大小

稀溶液10mL

产生蓝色絮状沉淀

豌豆大小

浓溶液10mL

产生蓝色絮状沉淀,并出现黑色固体

小科咨询老师后得知蓝绿色沉淀为碱式铜盐.

上一题 下一题 0.0难度 选择题 更新时间:2019-09-19 10:14:43

答案(点此获取答案解析)

同类题4

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

    All languages change over time, but some change at a faster rate than others. ____ The most important factors are the number of people who speak a language, where they live and whether they move around, the importance of the language for world trade and communication, and changes in technology.

    ____ However, today English is the most widely used language in the world. English is spoken by about 350 million people as a first language in countries such as Great Britain, the United States. In addition, about a billion more people speak English as a second language.

    English started to take over French as an international language during the period of British colonialism (殖民主义) when the English ruled many countries in Africa and Asia. ____ The colonial period came to an end at the same time that several other changes occurred. For example, the U.S. started to play a greater part in global affairs and the international economy. New means of communication technology such as television and the Internet spread English worldwide. ____ In addition, they could use the Internet for information, business, or e-mail communication, all in English. Just as the use of English spread, other languages changed English by contact or by new inventions and technology.

    In contrast, Icelandic is a language that has changed very slowly. Icelandic speakers today can understand poetry written in a slightly different dialect over 1,000 years ago! Why has Icelandic changed so slowly? The main reason is the isolated (孤立的) location of the island in the middle of the Atlantic Ocean. ____ Compared to England, Iceland had no history of colonialism. Iceland's small population has not played a major role in international trade or communication. Today, most Icelanders speak English in addition to their native language. With outside influences, Icelandic is changing more rapidly now.

A. People everywhere could watch the news or sports events in English.

B. These changes have a great influence on the development of society.

C. Isolation meant that for hundreds of years, Icelanders had little contact with speakers of other languages.

D. What are some of the factors that influence how quickly a language changes?

E. The language communication brings about the communication of technology.

F. In the past, other languages such as Latin or French were more important than English.

G. English was the primary means of communication in these colonies.