在化学反应2NaClO2+Cl2=2NaCl+2口中，“口”内物质的化学式是（_爱下问搜题

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问题选择题

在化学反应2NaClO₂+Cl₂=2NaCl+2口中，“口”内物质的化学式是（　　）

A．ClO₂

B．Cl₂O

C．NaClO

D．NaClO₃

答案

设“口”内物质的化学式是X，由反应的化学方程式Cl₂+2NaClO₂═2NaCl+2X，可知反应前的Cl₂与2NaClO₂共含Cl、Na、O三种原子的原子个数分别为4、2、4，而反应后中只含有2个Na原子与2个Cl原子，根据化学变化前后原子种类、个数不变，可判断2个X中应含有2个Cl原子、4个O原子，则物质X的化学式为ClO₂；

故选A．

阅读理解

任务型阅读。

Mr and Mrs Jones live(居住) in Paris. Mr Jones takes a bus to the bank(银行) every day. He is

a clerk. He often goes out in the morning and comes back in the evening. Mrs Jones works in a school.

She usually goes to work at eight in the morning and gets home at about five thirty in the afternoon. So

they have no time to look after their little son, Jerry. Who looks after Jerry? His aunt, Mary. She is Mr

Jones'sister.

据短文内容,回答下列问题.

1. Where do the Jones live?

______________________

2. What's Mr jones' jod?

___________________________

3. What time does Mrs Jones get home?

____________________________________

4. How many kids do they have?

________________________________

5. Who looks after jerry?

__________________________________

填空题

BSP方法能帮助企业形成信息系统的【15】和控制机制，改善对信息和数据处理资源的使用，从而成为开发企业信息系统的有效方法之一。