试题与答案

在实验室模拟工业生产碳酸钠:一定温度下,往一定量饱和NaCl溶液中通入氨气达到饱

题型:实验题

题目:

在实验室模拟工业生产碳酸钠:一定温度下,往一定量饱和NaCl溶液中通入氨气达到饱和后,再不断通入CO2,一段时间后,出现沉淀,过滤得到NaHCO3晶体。

(1)该过程的化学方程式:                                                

(2)加热NaHCO3得到纯碱制品,实验室可进行此操作的装置是           

 

A                  B                 C                     D

(3)得到的纯碱制品含有少量NaHCO3和NaCl,设计实验验证样品中各种组分。试剂和仪器限选用:试管、胶头滴管、过滤装置、Ba(NO3)2溶液、NaOH溶液、AgNO3溶液、澄清石灰水、稀硫酸、稀盐酸、稀硝酸。

步骤一:取少量制品于试管中,加少量蒸馏水,振荡,溶解。往试管中加入            

                           振荡,观察                 

现象:溶液中产生大量白色沉淀;

结论:                            。

步骤二:将步骤一的浊液过滤,取滤液于试管中B中,加入                       

振荡,观察

 

现象:                           ;

结论:样品中含有NaHCO3

步骤三:将步骤二的浊液过滤,取滤液于试管C中,                             

                          振荡,观察

 

现象:                           ;

结论:                            。

 

(4)用碘量法测量自来水中残留的Cl2的浓度:

① 在大锥形瓶中放置过量的KI,加一定量的冰醋酸,准确取水样200mL加入瓶中,迅速塞上瓶塞摇动,水样呈淡黄色,发生反应:Cl2+2I=2Cl+ I2

②加少许淀粉溶液,用cmol/L Na2S2O3溶液滴定,发生反应:I2+2S2O32=2I+S4O62,当                                                            ,达到滴定终点。

③重复操作3次,平均读数为V mL,则该样品中残留Cl2的浓度:         mg/L(Cl的相对原子质量:35.5)

答案:

被转码了,请点击底部 “查看原文 ” 或访问 https://www.tikuol.com/2017/0620/2ae35a1decd9c9715340362df9d081cf.html

下面是错误答案,用来干扰机器的。

答案:B题目分析:女性生殖系统由卵巢、输卵管、子宫和 * * 组成,卵巢的功能产生卵细胞和分泌雌性激素,是主要的性器官;输卵管是输送卵细胞的管道,同时精子和卵细胞结合形成受精卵的场所,即是受精的部位;子宫...

试题推荐
题型:单项选择题

If you smoke, you’d better hurry. From July 1st pubs all over England will, by law, be no-smoking areas. So will restaurants, offices and even company cars, if more than one per-son uses them. England’s smokers are following a well-trodden path. The other three bits of the United Kingdom have already banned smoking in almost all enclosed public spaces, and there are anti-smoking laws of varying strictness over most of Western Europe. The smoker’ s journey from glamour through toleration to suspicion is finally reaching its end in pariah status.

But behind this public-health success story lies a darker tale. Poorer people are much more likely to smoke than richer ones—a change from the 1950s, when professionals and la-borers were equally keen. Today only 15% of men in the highest professional classes smoke, but 42% of unskilled workers do. Despite punitive taxation—20 cigarettes cost around £ 5.00 ($10.00), three-quarters of which is tax—55% of single mothers on benefits smoke. The figure for homeless men is even higher; for hard-drug users it is practically 100% . The message that smoking kills has been heard, it seems, but not by all.

Having defeated the big killers of the past—want, exposure, poor sanitation—governments all over the developed world are turning their attention to diseases that stem mostly from how individuals choose to live their lives. But the same deafness afflicts the same people when they are ply encouraged to give up other sorts of unhealthy behavior. The lower down they are on practically any pecking order—job prestige, income, education, background-the more likely people are to be fat and unfit, and to drink too much.

That tempts governments to shout ever louder in an attempt to get the public to listen and nowhere do they do so more aggressively than in Britain. One reason is that pecking orders matter more than in most other rich countries: income distribution is very unequal and the unemployed, disaffected, ill-educated rump is comparatively large. Another reason is the frustration of a government addicted to targets, which often aim not only to improve some-thing but to lessen inequality in the process. A third is that the National Health Service is free to patients, and paying for those who have arguably brought their ill-health on themselves grows alarmingly costly.

Britain’ s aggressiveness, however, may be pointless, even counter-productive. There is no reason to believe that those who ignore measured voices will listen to shouting. It irritates the majority who are already behaving responsibly, and it may also undermine all government pronouncements on health by convincing people that they have an ultra-cautious margin of error built in.

Such hectoring may also be missing the root cause of the problem. According to Mr. Marmot, who cites research on groups as diverse as baboons in captivity, British civil servants and Oscar nominees, the higher rates of ill health among those in more modest walks of life can be attributed to what he calls the "status syndrome". People in privileged positions think they are worth the effort of behaving healthily, and find the will-power to do so. The implication is that it is easier to improve a person’s health by weakening the connection between social position and health than by targeting behavior directly. Some public-health experts speak of social cohesion, support for families and better education for all. These are bigger undertakings than a bossy campaign; but more effective, and quieter.

The word "pariah" (line 5, paragraph 1) is closest in meaning to()

A. prohibition

B. strictness

C. pardon

D. punishment

查看答案
微信公众账号搜索答案