问题 实验题

(8分)已知Fe(OH)2是白色难溶于水的物质,很容易被空气中的氧气氧化为Fe(OH)3。如图所示装置可用来制取和观察Fe(OH)2在空气中被氧化时颜色的变化。实验时必须使用铁屑和6mol/L的硫酸,其它试剂自选。

请填写下列空白:

(1)B中盛有一定量的NaOH溶液,A中应预先加入的试剂是                         

(2)实验开始时应先将活塞E   (填“打开”或“关闭”),C中收集到的气体的主要成份是          

(3)简述生成Fe(OH)2的操作过程                                              

(4)(3)操作后拔出装置B中的橡皮塞,使空气进入,写出有关反应的化学方程式

                                                                                 

答案

(8分)

(1)铁屑(1分)     (2)打开(1分)      H2(1分)

(3)关闭活塞E,使FeSO4溶液被压入B瓶中进行反应(2分)

(4)4Fe(OH)2+O2+2H2O=4Fe(OH)3(3分)

题目分析:根据实验目的:制取和观察Fe(OH)2在空气中被氧化时颜色的变化,则A装置是制取硫酸亚铁溶液,B装置是生成氢氧化亚铁沉淀,同时利用氢气排除A、B装置内的空气。

(1)应该预先加入铁粉与稀硫酸反应产生亚铁离子及氢气;

(2)先将活塞E打开,主要是利用氢气赶走装置内的空气,C中收集到得主要是氢气;

(3)等空气被赶走后,关闭E,此时氢气出不去,装置A中的压强越来越大,会使硫酸亚铁流入B装置,生成白色沉淀氢氧化亚铁。

(4)空气中氧气会氧化氢氧化亚铁,很快会看到白色沉淀转化为灰绿色沉淀,最后变为红褐色沉淀氢氧化铁。方程式:4Fe(OH)2+O2+2H2O=4Fe(OH)3

点评:涉及知识点都是高中重点训练的知识,学生掌握熟练,本题难度不大。

单项选择题

It is no longer just dirty blue-collar jobs in manufacturing that are being sucked offshore but also white-collar service jobs, which used to be considered safe from foreign competition. Telecoms charges have tumbled, allowing workers in far-flung locations to be connected cheaply to customers in the developed world. This has made it possible to offshore services that were once non-tradable. Morgan Stanley’s Mr. Roach has been drawing attention to the fact that the "global labour arbitrage" is moving rapidly to the better kinds of jobs. It is no longer just basic data processing and call centres that are being outsourced to low-wage countries, but also software programming, medical diagnostics, engineering design, law, accounting, finance and business consulting. These can now be delivered electronically from anywhere in the world, exposing skilled white-collar workers to greater competition.

The standard retort to such arguments is that outsourcing abroad is too small to matter much. So far fewer than lm American service-sector jobs have been lost to off-shoring. Forrester Research forecasts that by 2015 a total of 3.4m jobs in services will have moved abroad, but that is tiny compared with the 30m jobs destroyed and created in America every year. The trouble is that such studies allow only for the sorts of jobs that are already being off-shored, when in reality the proportion of jobs that can be moved will rise as IT advances and education improves in emerging economies.

Alan Blinder, an economist at Princeton University, believes that most economists are underestimating the disruptive effects of off-shoring, and that in future two to three times as many service jobs will be susceptible to off-shoring as in manufacturing. This would imply that at least 30% of all jobs might be at risk. In practice the number of jobs off-shored to China or India is likely to remain fairly modest. Even so, the mere threat that they could be shifted will depress wages:

Moreover, says Mr. Blinder, education offers no protection. Highly skilled accountants, radiologists or computer programmers now have to compete with electronically delivered competition from abroad, whereas humble taxi drivers, janitors and crane operators remain safe from off-shoring. This may help to explain why the real median wage of American graduates hat fallen by 6% since 2000, a bigger decline than in average wages.

In the 1980s and early 1990s, the pay gap between low-paid, low-skilled workers and high-paid, high-skilled workers widened significantly. But since then, according to a study by David Autor, Lawrence Katz and Melissa Kearney, in America, Britain and Germany workers at the bottom as well as at the top have done better than those in the middle-income ’group. Office cleaning cannot be done by workers in India. It is the easily standardised skilled job in the middle, such as accounting, that are now being squeezed hardest. A study by Bradford Jensen and Lori Kletzer, at the Institute for International Economics in Washington D. C., confirms that workers in tradable services that are exposed to foreign competition tend to be more skilled than workers in non-tradable services and tradable manufacturing industries.

Which of the following statements is the typical reply concerning off-shoring()

A. Service-sector has sustained a great loss

B. White-collar workers will not have a narrow escape

C. Most economists underestimated the effects of off-shoring

D. Outsourcing abroad has no significant impact

单项选择题