问题 选择题

FeS与一定浓度的HNO3反应,生成Fe(NO3)3、Fe2(SO4)3、NO2、N2O4、NO和H2O,当NO2、N2O4、NO的物质的量之比为1:1:1时,实际参加反应的FeS与HNO3的物质的量之比为

A.1:6

B.2:15

C.2:11

D.1:7

答案

答案:D

设生成NO2、N2O4、NO的物质的量均为1mol,则被还原的HNO3物质的量为4mol,共得到6mol电子;1molFeS在反应中失去9mol电子,故被氧化的FeS物质的量为mol,生成物中 Fe2(SO4)3的物质的量是mol,Fe(NO3)3的物质的量也是×(×2)mol,即反应中有mol HNO3生成了盐,因此共有mol HNO3参加反应,实际参加反应的FeS与HNO3的物质的量之比为mol: mol =1:7,D正确。

阅读理解

阅读理解。

     In order to know a foreign language thoroughly (完全地), four things are necessary. First, we must

understand the language when we hear it spoken. Secondly, we must be able to speak it ourselves, with

confidence(自信) and without hesitation (犹豫). Thirdly, we must do much reading. Finally, we must be

able to write it. We must be able to make sentences that are correct in grammar.

    There are no shortcuts to success in language learning. A good memory is a great help, but it is not

enough only to memorize the rules from a grammar book. It is not much learning by heart long lists(一

览表) of words and their  meanings, studying the dictionary and so on. We must learn by using the

language.

     If we are pleased with a few rules we have memorized, we are not really learning the language. We

must "learn through use." Practice is important. We must practise speaking and writing the language

whenever we can.

1. The most important things to learn a foreign language are _____. 

A. understanding and speaking  

B. listening, speaking, reading and writing

C. writing and understanding      

D. memorizing and listening

2. Someone hears and writes English very well, but he speaks it very badly. This is because _____.  

A. he doesn't understand the language when he hears it spoken

B. he doesn't have a good memory

C. he always remembers lists of words and their meanings

D. he often hesitates(犹豫) to practise speaking it

3. One can never learn a foreign language well by _____. 

A. doing much practice       

B. studying the dictionary

C. learning through use        

D. using the language

4. Which is the most important in learning a foreign language?  

A. A good memory.  

B. Speaking.      

C. Practice.    

D. Writing.

5. "Learn through use" means _____. 

A. we use a language in order to learn it  

B. we learn a foreign language in order to use it

C. we can learn a language well while we are keeping using it      

D. B and C.

单项选择题