问题 问答题 简答题

一台输送请水的离心泵,现用来输送容重为水的1.3倍的液体,该液体的其他物理性质视为与水相同,另外水泵装置也相同,问:(1)该水泵工作时,其流量与扬程关系曲线有无改变?在相同的工作状况下,压力表读数如何变化?输送清水时,水泵的压力扬程为0.5Mpa。(2)如果水泵将液体输往高地密闭水箱时,密闭水箱内的压力为2atm(如下图),试求此时的静扬程HST?

 

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实验题

(15分)下图中,甲由C、H、O三种元素组成,元素的质量比为12:3:8,甲的沸点为78.5℃,其蒸气与H2的相对密度是23。将温度控制在400℃以下,按要求完成实验。

(1)在通入空气的条件下进行实验Ⅰ。

①甲的名称是               ,加入药品后的操作依次是                  

a.打开活塞                   b.用鼓气气球不断鼓入空气        c.点燃酒精灯给铜丝加热

②实验结束,取试管中的溶液与新制的Cu(OH)2混合,加热至沸腾,实验现象为

                                                                    

③现用10%的NaOH溶液和2%的CuSO­4溶液,制取本实验所用试剂Cu(OH)2,请简述实验操作。

                                                                    

(2)在停止通入空气的条件下进行实验Ⅱ。

①关闭活塞,为使甲持续进入反应管中,需要进行的操作是                  

                                 

②甲蒸气进入反应管后,在铜做催化剂有250~350℃条件下发生可逆的化学反应,

在试管中收集到了实验Ⅰ相同的产物,并有可燃性气体单质放出。该反应揭示了甲

催化氧化的本质。写出实验Ⅱ中反应的化学方程式,并结合该化学方程式简要说明实验Ⅰ中所通空气的作用。

                                              

单项选择题

When Dr. John W. Gofman, professor of medical physics at the University of California and a leading nuclear critic, speaks of "ecocide" in his adversary view of nuclear technology, he means the following. A large nuclear plant like that in Kalkar, the Netherlands, would produce about 200 pounds of plutonium each year. One pound, released into the atmosphere, could cause 9 billion cases of lung cancer. This waste product must be stored for 500,000 years before it is of no further danger to man. In the anticipated reactor economy, it is estimated that there will be 10,000 tons of this material in Western Europe, of which one table-spoonful of plutonium-239 represents the official maximum permissible body burden for 200,000 people. Rather than being biodegradable, plutonium destroys biological properties.

In 1972 the .U.S. Occupational Safety and Health Administration ruled that the asbestos level in the work place should be lowered to 2 fibers per cubic centimeter of air, but the effective date of the ruling has been delayed until now. The International Federation of Chemical and General Workers’ Unions report that the 2-fiber standard was based primarily on one study of 290 men at a British asbestos factory. But when the workers at the British factory had been reexamined by another physician, 40--70 percent had X-ray evidence of lung abnormalities. According to present medical information at the factory in question, out of a total of 29 deaths thus far, seven were caused by lung cancer. An average European or American worker comes into contact with six million fibers a day. "We are now, in fact, finding cancer deaths within the family of the asbestos worker," states Dr. Irving Selikoff, of the Mount Sinai Medical School in New York.

It is now also clear that vinyl chloride, a gas from which the most widely used plastics are made, causes a fatal cancer of the blood-vessel cells of the liver. However, the history of the research on vinyl chloride is, in some ways, more disturbing than the "Watergate cover- up. " "There has been evidence of potentially serious disease among polyvinyl chloride workers for 25 years that has been incompletely appreciated and inadequately approached by medical scientists and by regulatory authorities," summed up Dr. Selikoff in the New Scientist. At least 17 workers have been killed by vinyl chloride because research over the past 25 years was not followed up. And for over 10 years, workers have been exposed to concentrations of vinyl chloride 10 times the "safe limit" imposed by Dow Chemical Company.

It can be inferred from the text that the author believes that()

A. nationwide application of anti-pollution devices can finally prevent cancer

B. tough legislation is needed to set lower limits of worker exposure to harmful chemicals

C. more research is required into the causes of cancer before further progress can be made

D. industrialization must be slowed down to prevent further spread of cancer-causing agents