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问题 选择题

常温时,将V1mL c1 mol/L的氨水滴加到 V2mL c2 mol/L 的盐酸中，则

小题1:若混合溶液的pH=7，则 c1V1      c2V2； c(NH4+)         c(Cl-)（填>、=或<，下同）

小题2:若混合溶液的pH＞7，则c1V1      c2V2； c(NH4+)         c(Cl-)

小题3:若V1=V2、c1= c2，则混合溶液中离子浓度的大小关系为            。若此时溶液的pH=a,则由水电离出来的H＋的浓度_________ mol·L-1，并写出下列算式的数学表达式： c(Cl-)—c(NH4+)＝________________ mol·L-1

小题4:若V1=V2，且混合溶液的pH<7，则一定有c1< c2吗？请说明理由     。

答案

小题1:  >   =

小题2:  >  >

小题3:c(Cl-)＞c(NH4+)＞c(H+)＞c(OH-)   ;10-a ;    10-a-10a-14

小题4:不一定，c1= c2时，两者恰好反应生成NH4Cl溶液，pH<7，c1＞c2时，pH也可能小于7。

考查酸碱中和的有关计算以及溶液中离子浓度大小关系的比较。

小题1:氨水是弱碱，若氨水和盐酸恰好反应，生成物氯化铵水解，溶液显酸性。若溶液显中性，则说明氨水过量，即c1V1＞c2V2。根据电荷守恒c(NH4+)＋c(H+)＝c(OH-)＋c(Cl-)可知，当溶液显中性 即c(H+)＝c(OH-)时，c(NH4+)＝c(Cl-)。

小题2:若混合溶液的pH＞7，则氨水仍然是过量的，即c1V1＞c2V2。根据电荷守恒c(NH4+)＋c(H+)＝c(OH-)＋c(Cl-)可知，此时c(NH4+)＞c(Cl-)。

小题3:若V1=V2、c1= c2，则二者恰好反应，溶液中只有氯化铵，则混合溶液中离子浓度的大小关系为c(Cl-)＞c(NH4+)＞c(H+)＞c(OH-)。NH4+结合水电离出的OH－，促进水的电离，所以溶液中的氢离子就是水电离出的氢离子，即浓度为10-a mol/L。根据电荷守恒可知c(Cl-)－c(NH4+)＝c(H+)－c(OH-)＝10-a-10a-14 mol/L。

小题4:溶液显酸性，有可能水盐酸过量，也有可能水生成的氯化铵水解导致的。即使氨水过量，如果氯化铵的水解程度大于氨水的电离程度，溶液仍然会显酸性。例如：当c1= c2时，两者恰好反应生成NH4Cl溶液，pH<7。

单项选择题

某一上市公司股票在一年后支付的股利预计为2元，并该公司股票的股利能保证4%的增长速度，该股票的预计收益率为12%，按照稳定增长模型，该股票购买时的价格为（）元。

A.15

B.20

C.25

D.30
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阅读理解

There is no doubt that much of the profit of a business—sometimes the whole of its success—depends upon the use of the odds and ends．The odds and ends are various small things，which are left over when the main things are produced．But they possess a real value of their own．

If a business，big or small，looked down upon these odds and ends，it would mean a big difference in the amount of the benefit of the business．Take a meat factory for instance， there are countless odds and ends—bones and hair，which can be made into glue and rope to increase its profit greatly．

Then，if we are college students，what about our odds and ends—the odd moments？ Take time for example．Every one of us has the exact same amount of it．Everyone’s success or failure depends on the use of their time．But everyone uses the time more or less in the same way．However，why many great men in science or art have made huge successes for themselves in the world？Because they have made best use of their odd moments．Take Thomas A．Edison， he never allowed his odd moments to slip by．He thought，planned，and tried his inventions．He always worked twenty hours out of each twenty-four．His inventions made him famous all over the world，and provided valuable wealth for the human beings．

So, remember this axiom：very busy people always find time for everything．However，people with great spare time find time for nothing．Is it very strange？Not at all！The question is how to gather up fragments of time and make full use of them．As many big businesses have found，that the real profit is in using the odds and ends．We also must do in this way to make best use of our odd moments and manage to be successful in something that we do．

小题1: What are odds and ends？

A．They are nothing useful．

B．They are various small，but valuable things．

C．They are the main things that factories produce．

D．They are odd moments students deny to gather up．小题2: Why should the odds and ends be made full use of ？Because  ____   ．

A．lots of factors in success or in failure depend on the best use of odds and ends

B．they control to possess a value of their own

C．they are various small things people don’t want

D．they are useless things left over when the main things are produced小题3:What does the word “Axiom” in the fourth paragraph mean?

A．clear and evident without proof

B．statement accepted as true without proof of argument

C．statement that can be argued

D．regulation accepted in scientific usage小题4: “Fragments of time” equals  “____   ”in the above passage．

A．the odds and ends

B．immense leisure

C．the main things

D．the odd moments
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