问题 计算题

(4分)工业上常用电解熔融氧化铝来制备金属铝,其主要反应方程式为:

2Al2O34Al +3R↑。

(1)其中R的化学式为        

(2)若电解204吨氧化铝可生产金属铝多少吨?

答案

(1)O2   1分  (2)108t

(1)根据质量守恒定律,化学反应前后原子的种类和数目不变确定R的化学式.

(2)利用该反应的化学方程式,根据氧化铝的质量求出铝的质量.

(2)(3分)解:设可生产金属铝的质量为x。

2Al2O34 Al+3O2

204        108

204吨       x

   x=108t

答:可生产金属铝108t。

填空题
阅读理解

Being the boss might mean more money and challenging work but it can also cause damage to physical and mental well-being, according to a Canadian study.

For years studies have shown people in lower-status jobs generally have higher rates of heart disease and other illnesses and die earlier than those in higher-status positions while job authority has shown no relationship with workers’ health.

But University of Toronto researchers, using data from 1,800 US workers, found the health of people in higher positions is affected by work as they are more likely to report conflicts with co-workers and say work disturbs their home life.

However, the positive aspects of having a power position at work, such as higher status, more pay and greater independence, seemed to cancel out the negative aspects when it came to people’s physical and psychological health.

These latest findings, reported in the journal Social Science & Medicine, suggest that the advantages and disadvantages authority positions basically cancel each other out, giving the general impression that job authority has no health effects.

For the study, the researchers surveyed participants about various aspects of their work, life and well-being. Job authority was judged based on whether a person managed other employees and had power over hiring, firing and pay.

Physical health complaints included problems like headaches, body aches, heartburn and tiredness. Psychological complaints included sleep problems, difficulty concentrating and feelings of sadness, worry and anxiety.

“This isn’t to suggest that having authority is ‘bad’—in fact, we show it has benefits ... but it is important to identify the negative sides and deal with them.” researcher Scott Schieman said.  

Schieman said conflicts with co-workers or involvement of work into home life may destroy at physical and mental well-being by creating stress.

“These are key stressors that can tax individuals’ ability to function effectively,” Schieman said.

56. Work will have a negative effect on job authority’s health probably because __________.

A. they are not fit for their work

B. they have power over hiring and pay

C. they are faced with severe competition

D. they don’t get on well with their co-workers

57. Most people don’t see that bosses have health effects because __________.

A. their health problems are not serious enough to see

B. they have enough money to keep themselves healthy

C. their problems are quite different from those of workers  

D. the advantages and disadvantages of their status work against each other

58. From the passage we can infer that the study aims to _________.

A. warn people not to be a boss for ever

B. remind the boss to deal with the bad effects of their work

C. show that having authority is harmful to one’s health

D. prove that being a boss can benefit a lot 

59. The best title for this passage might be ________.

A. Lower-status can affect health                  B. Authority can affect health

C. Positive aspects of a power position          D. Disadvantages of being a boss