问题 选择题

下列做法不是为达到加快化学反应速率目的的是(   )

A.锅炉中的煤燃烧时要鼓入大量空气

B.高炉炼铁时将铁矿石粉碎

C.用红磷测定空气中氧气含量时,红磷要过量

D.用过氧化氢制氧气时加二氧化锰

答案

答案:C

题目分析:锅炉中的煤燃烧时要鼓入大量空气,使燃烧更旺,反应更快;高炉炼铁时将铁矿石粉碎,使反应更快;用红磷测定空气中氧气含量时,红磷要过量是为了耗尽装置内的氧气,跟反应速率无关;用过氧化氢制氧气时加二氧化锰,是为了让反应速率更快。选C。

点评:题中的常考点是催化剂,催化剂能改变化学反应的速率,但化学反应前后,其本身的化学性质和质量都不变。

问答题 简答题
阅读理解

阅读理解。

      Being a youth (青年) is one thing, and being a good one is another. A good youth should have these

qualities(品质): First of all, health. A healthy body is the best riches (财富). Without it, nothing can be

done well. If you are poor in health, you will have to take medicine day after day. Even you can't work,

do sports and so on. Secondly, one must have a kind heart. Always do something for others. Help those

in trouble and care about the people around you. If everyone did the same, what a wonderful world it

would be! Thirdly, one must have the ability(能力) to work with others. Cooperation (合作) and

communication are two important keys to better human relations (关系). Everyone needs friends because

no one can live through life alone.

      Patriotism is also something we should never forget. Patriotism means a love for one's country. It is

one of the highest qualities of humans'. Everyone should love his country. But people sometimes think that

patriots (爱国者) must be fighters fighting for their country in hard times. That is wrong. A good youth's

work is not only fighting. A good youth will do the things his country asks him to do. 

      I think a good youth of today should also have some training in art. If everyone can enjoy art and be

able to make more of it for others, then people will live better and enjoy more.

根据短文内容,回答问题。

1.What is the most important quality should a youth have?

      ___________________________________________________________

2.If you want to have better human relations with others, what are very important?

      ___________________________________________________________

3.What does "patriotism" mean?

       ___________________________________________________________

4.Patriots are the fighters only fighting for their countries in hard times, aren't they?

      ___________________________________________________________

 5.How many qualities should a good youth have in the writer's eyes? 

      ____________________________________________________________