搜题请搜索小程序“爱下问搜题”
问题 问答题

取1.43g Na2CO3•10H2O溶于水配成100mL溶液，求：

（1）Na2CO3溶液的物质的量浓度

（2）Na+物质的量浓度

（3）取出20ml该溶液用水稀释，使Na2CO3溶液的物质的量浓度变为0.004mol/L，求加入水的体积（设稀释时，对溶液体积的影响忽略不计）

答案

（1）n（Na2CO3•10H2O）=

1.43g
286g/mol
=0.005mol，

c（Na2CO3）=

0.005mol
0.1L
=0.05mol/L，

答：Na2CO3溶液的物质的量浓度为0.05mol/L．

（2）c（Na+）=2c（Na2CO3）=2×0.05mol/L=0.1mol/L，

答：Na+物质的量浓度为0.1mol/L．

（3）20ml该溶液，n（Na2CO3）=0.02L×0.05mol/L=0.001mol，

设加入水的体积为VL，

则

0.001mol
0.02L+VL
=0.004mol/L，解之得V=0.23，即230ml，

答：加入水的体积为230mL．

多项选择题

少尿时血液透析的指征（）。

A.血肌酐＞422μmol／L

B.急性左心功能衰竭

C.脑水肿

D.血钾＞6.5mmol／L

E.酸中毒
查看答案
单项选择题

It is quite reasonable to blame traffic jams, the cost of" gas and the great speed of modern life, but manners on the toad are becoming horrible. Eye,body knows that the nicest men would become fierce tigers behind the wheel. It is all right to have a tiger in a cage, but to have one in the driver’s seat is another matter.
Road politeness is not only good manners, but good sense too. It takes the most cool-headed drivers great patience to give up the desire to beat back when forced to face rude driving. On the other hand, a little politeness goes a long way towards reducing the possibility of quarrelling and fighting. A friendly nod or a wave of thanks in answer to an act of politeness helps to create an atmosphere of good will and calmness so necessary in modern traffic conditions. But such behaviors of politeness are by no means enough. Many drivers nowadays don’t even seem able to recognize politeness when they see it.
However, misplaced politeness can also be dangerous. Typical examples are the driver who waves a child crossing the street at a wrong place into the path of oncoming cars that may be not able to stop in time. The same goes for encouraging old ladies to cross the road wherever and whenever they want to.
An experienced driver, whose manners are faultless, told me it would help if drivers learnt to correctly join in traffic stream without causing total blockages that give rise to unpleasant feelings. Unfortunately, modern drivers can’t even learn to drive,let alone master the roadmanship. Years ago, experts warned us that the fast increase of the car ownership would demand more give-and-take from all road users. It is high time for all of us to take this message to heart.

The following statements are right EXCEPT that______.

A. some modern drivers are not good at driving
B. road politeness is good sense as well as good manners
C. it is also right to have a tiger in the driver’s seat
D. a friendly driver should nod or wave thanks in answer to an act of politeness
查看答案