问题 问答题

常温下,下列各组离子在指定溶液中一定能大量共存的是(  )

A.1.0mol▪L-1的KNO3溶液:H+、Fe2+、Cl-、SO42-

B.甲基橙呈红色的溶液:NH4+、Ba2+、AlO2-、Cl-

C.pH=12的溶液:K+、Na+、CH3COO-、Br-

D.与铝反应产生大量氢气的溶液:Na+、K+、CO32-、NO3-

答案

A、在酸性条件下,NO3-离子具有强氧化性,Fe2+离子具有还原性,二者发生氧化还原反应而不能大量共存,故A错误;

B、甲基橙呈红色的溶液呈酸性,AlO2-离子与H+离子反应而不能大量共存,故B错误;

C、pH=12的溶液呈碱性,在碱性条件下,这四种离子不发生任何反应,能大量共存,故C正确;

D、与铝反应产生大量氢气的溶液可能是酸溶液,也可能是碱溶液,在酸性条件下CO32-离子与H+离子反应而不能大量共存,故D错误.

故选C.

单项选择题
单项选择题

Informal conversation is an important part of any business relationship. Before you start a discussion, however, make sure you understand which topics are suitable and which are considered taboos in a particular culture. Latin Americans enjoy sharing information about their local history, art, and customs. They expect questions about their family and are sure to show pictures of their children. Yon may feel free to ask similar questions of your Latin American friends. The French think of conversation as an art form, and they enjoy the value of lively discussions as well as disagreements. For them, arguments can be interesting—and they can cover pretty much or any topic—as long as they occur in a respectful and intelligent manner.

In the United States, business people like to discuss a wide range of topics, including opinions about work, family, hobbies, and politics. In Japan, China, and Korea, however, people are much more private. They do not share much about their thoughts, feelings, or emotions because they feel that doing so might take away from the harmonious business relationship they’re trying to build. Middle Easterners are also private about their personal lives and family matters. It is considered rude, for example, to ask a businessman from Saudi Arabia about his wife or children.

As general rule, it’s best not to talk about politics or religion with your business friends. This can get you into trouble, even in the United States, where people hold different views. In addition, discussing one’s salary is usually considered unsuitable. Sports is typically a friendly subject in most parts of the world, although be careful not to criticize a national sport. Instead, be friendly and praise your host’s team.

The author considers politics and religion()

A. cheerful topics

B. taboos

C. rude topics

D. topics that can never be talked about