问题 填空题

已知某无色溶液,其溶质可能是氯化钠、硫酸钠、氢氧化钠、碳酸钠、氢氧化钙等五种物质中的一种或几种,为确定其成分实验如下:

(1)测其PH值,该溶液的pH=13;

(2)取样,向其中加入过量的稀盐酸,刚开始时无明显现象,过一段时间后有气泡产生;

(3)将上述反应后的溶液蒸发干,得到一种纯净物晶体

根据以上实验现象,请判断该溶液中一定含有______;一定不含______;可能含有______.请写出生成气体的化学反应方程式:______.

答案

(1)溶液的pH=13,溶液显碱性,可能是氢氧化钠、碳酸钠、氢氧化钙,但碳酸钠和氢氧化钙不能共存,因此不能同时存在;

(2)取样,向其中加入过量的稀盐酸,刚开始时无明显现象,过一段时间后有气泡产生,说明盐酸先和碱发生酸碱中和反应,再和碳酸钠反应产生气泡,因此一定含有碳酸钠,而碳酸钠和氢氧化钙不能共存,因此一定没有氢氧化钙,则一定含有的碱是氢氧化钠;

(3)将反应后的溶液蒸发干,得到一种纯净物晶体,结合(2)中碳酸钠和盐酸反应产生氯化钠,因此一定不含有硫酸钠,可能含有氯化钠;

因此根据以上实验现象,该溶液中一定含有氢氧化钠、碳酸钠;一定不含有氢氧化钙、硫酸钠;可能含有氯化钠;碳酸钠和盐酸反应产生二氧化碳,反应的方程式为:Na2CO3+2HCl═2NaCl+H2O+CO2↑;

故答案为:氢氧化钠、碳酸钠;氢氧化钙、硫酸钠;氯化钠;Na2CO3+2HCl═2NaCl+H2O+CO2↑.

阅读理解

Why are first ladies so important in the United States? They are unpaid and have no official work? There are several reasons, but the most important reason is they are role models for other women in the United States.

Jacqueline Kennedy was the best first lady in the US. Although she wasn't an actress, model or singer, she was a fashion and cultural icon(文化偶像) who charmed people wherever she went.

If you are looking for someone who is as charming as Jacqueline Kennedy, it will be hard to find anyone more suitable than Peng Liyuan, wife of Chinese President Xi Jinping. If you were writing a novel and trying to describe the perfect mixture of personal history, capabilities, confident lady for a character, you'd come up with someone like Peng.

Born into a family in Shandong province, she joined the People's Liberation Army(中国人民解放军) at the age of 18, doing pretty well in singing military(军旅) songs. But she is not only famous for her voice and great achievements, but also for her charity efforts. She has, among other things, worked as a member of World Health Organization to fight against AIDS, and has done much in 2008 Sichuan earthquake.

The media(媒体) reported Peng’s trip with her husband. This was Xi’s his first foreign trip as president. The trip shows that she can be a role model for Chinese women, especially young Chinese women at home and abroad.

In the past, China has not had a tradition of first ladies like in the US. Now that China has a higher position on the world stage, it can have its first lady! And Peng Liyuan is the perfect person with whom to begin.

小题1:Why are first ladies important in the US?

A.Because they are unpaid.

B.Because they have official work.

C.Because they are role models for other women in the US.

D.Because they are more important than other women in the US.小题2:Why does the writer think Jacqueline Kennedy was the best first lady in the US?

A.Because she was an actress.

B.Because she was fashionable.

C.Because the writer likes to listening to her songs.

D.Because she attracted people wherever she went.小题3:Which is NOT right according to the passage?

A.Peng Liyuan is as charming as Jacqueline Kennedy.

B.Peng Liyuan wrote military songs from the age of 18.

C.The writer thinks Peng Liyuan is the most suitable first lady.

D.Peng Liyuan is famous not only for her voice and great achievements, but also for her charity work.小题4:Which may be the best title for the passage?

A.Jacqueline Kennedy

B.First ladies in the US.

C.First Ladies in China

D.Peng Liyuan, the perfect first lady to begin with.

选择题