问题 选择题

A在高温下分解2A(g)=B(g)+3C(g),若这一反应在固定容积的容器中进行,A完全分解后,容器内混合气体的密度是A密度的(   )
A.2倍B.相同C.0.5倍D.0.25倍

答案

B

本题考查密度的定义

反应2A(g)=B(g)+3C(g)在固定容积的容器中进行,反应前后混合气体的体积没有变化,而反应前后混合气体的总质量也没有变化,则A完全分解后,容器内混合气体的密度与反应产气体的密度一致,即与A的密度相同。

故正确答案为B

单项选择题

Are you going to high school to go on with your study What will you do if you can’t Don’t worry. Vocational schools are open for you because our country is in need of people with special skills.

Compared with common high schools, vocational schools have more advantages. Firstly, in order to promote the development of vocational education, our country spends a lot of money on it. So you need to pay only a smaller half of the school fee. Secondly, in here you have already started learning practical skills that you can use all your life. But some other students may still worry about how to spend the long three years at high schools. Why Because they didn’t choose the school that suits them. And finally, when they are still wondering where to go, you are already able to live on your own hands proudly. And perhaps it won’t be long before you are on the road to success.

People take different roads because they have different potentials. So different students should choose different schools. Go to high school if you think that you can go farther on that road. Choose a key high school if you are lucky enough to have the chance. Enter a vocational school if you are interested in the lessons there and you are better at making things with your hands.

In a word, think carefully and see what kind of person you are. Remember, always choose things that suit you.

This passage is written to ().

A.advise some students to choose vocational schools

B.talk about the advantages of common high schools

C.discuss how to divide students into different groups

D.compare different schools

单项选择题 A1/A2型题