问题 选择题

某温度下,在一容积不变的密闭容器中,A(g)+2B(g)⇌3C(g)达到平衡时,A.B和C的物质的量分别为3mol、2mol和4mol,若温度不变,向容器内的平衡混合物中再加入A、C各lmol,此时该平衡移动的方向为(  )

A.向左移动

B.向右移动

C.不移动

D.无法判断

答案

方法一:假设容器体积为1L,达到平衡时,A、B和C的物质的量分别为3mol、2mol和4mol,则浓度分别为3moL/L、2mol/L、4mol/L,平衡常数为k=

43
22
=
16
3

向容器内的平衡混合物中再加入A、C各lmol,此时A、B和C的浓度分别为4moL/L、2mol/L、5mol/L,

则此时QC=

53
22
=7.8125>
16
3
=5.333,

则平衡向左移动,

方法二:可用运用一边倒法,达到平衡后把C的量转化到 A、B,可以得到A、B的物质的量比值为13:14;另外添加如果是还保持这个比例,则平衡不移动,假设在另一个相同容器中加入A、C各lmol,把C的量转化到A、B,可得到A、B的物质的量比值为2:1=13:6.5,压入同一体积容器,相当于减少了B的物质的量 即减小其浓度导致平衡左移.

故选A.

阅读理解

阅读理解。

   The world is not only hungry, but it is also thirsty for water. This may seem strange to you, since nearly

70% of the earth's surface (表面) is covered with water. But about 97% of that is sea water, or salt water.

Man can only use the other 3% the fresh water from rivers, lakes, underground, and other sources (源泉).

And we can not even use all of that. Even worse, some of it has been made dirty.

    However, as things stand today, this fresh water is still enough for us. But our need for water is becoming

larger and larger quickly-almost day by day. We should take steps to do with this problem now and in this

way we can get away from a serious world-wide water shortage (缺乏) later on.

    We all have to learn how to stop wasting (浪费) our valuable water. One of the first steps is to develop

(开发) ways of reusing it. Today in most large cities, water is used only once and then sent out into a sewer

system(下水道). From there it returns to sea or runs into underground places. But even if every large city

reused its water, we still would not have enough. All we'd have to do to make use of sea water in the world

is to remove the salt. If we take these we will be in no danger of drying up.

1. The world is thirsty for water because ___. [ ]

A. man has not got enough food to eat

B. we haven't got enough fresh water

C. only 70% of the earth's surface is water

D. more water is sent into sewer system

2. The underlined word "valuable" means ___ and ___. [ ]

A. much, salty

B. fresh, enough

C. dear, useful

D. clean, helpful

3. What should we do if we want to have enough fresh water? ___. [ ]

A. Make full use of the sea water

B. Carry salt water into lakes or rivers

C. Try to save the fresh water as much as possible

D. Do our best to use the water again

4. The best but the most difficult way to solve (解决) the water problem of the world is to ___. [ ]

A. remove the salt from sea water

B. make the water in cities clean

C. take the water from underground

D. make the need for water smaller

5. What is the best title for this passage? ___. [ ]

A. The Importance of the Water

B. The World's Water Problem

C. The Thirsty World

D. Fresh Water and Sea Water

问答题 简答题