搜题请搜索小程序“爱下问搜题”
问题 计算题

已知用赤铁矿石冶炼铁的化学方程式为Fe2O3＋3CO2Fe＋3CO2请计算：(相信你一定能行！)

(1)Fe2O3的相对分子质量为________；

(2)现有2000吨含氧化铁80%的赤铁矿石，其中含氧化铁________吨；

(3)用此2000吨含氧化铁80%的赤铁矿石，理论上可以炼出纯铁多少吨？(要求有计算步骤)

答案

(1)160(1分)(仅列式，记0.5分)

(2)1600(1分)(仅列式，记0.5分)

(3)解：设可以炼出纯铁的质量为x。(0.5分)

160   2×56

1600吨 x(0.5分)

x＝1600吨×2×56/160＝1120吨(列式0.5分，答案正确0.5分)

答：可以炼出纯铁1120吨。(其他合理解法均可记分)

：（1）由氧化铁的化学式为Fe2O3，

则相对分子质量为56×2+16×3=160，故答案为：160；

（2）由矿石2000吨，含氧化铁80%，

则氧化铁的质量为2000t×80%=1600t，故答案为：1600；

（3）解：设可以炼出纯铁的质量为xt，则

Fe2O3+3CO2Fe+3CO2

160           2×56

1600t             x

160：2×56=1600t：x，

解得x=1120t，

答：可以炼出纯铁1120吨．

单项选择题

关于结合胆红素和非合胆红素的说法，不正确的是

A．尿胆原与空气接触转变成尿胆素
B．尿胆原、尿胆素、尿胆红素统称为尿三胆
C．结合胆红素进入肠道转变成尿胆原
D．非结合胆红素不溶于水
E．尿胆原在粪中排出变成粪胆原
查看答案
填空题


In the following passage, there are 25 blanks representing words that are missing from the context. You are to put back in each of the blanks the missing word. Write your answers on the ANSWER SHEET. The time for this section is 25 minutes.
Of all the employed workers in the United States, 12.5 million are part of a temporary workforce. The United States Bureau of Labor Statistics counts 9.2 percent of workers as those who have (1) they term "alternative employment arrangements." The government predicts that temporary staffing agencies (2) experience growth of 49 percent by 2010. If numbers increase at the rate (3) , these companies will add 1.9 million new jobs by 2010. That’s more than any (4) industry.
Temporary workers were the first ones to be affected by the recent economic recession, but they are (5) to be the first to regain positions as the economy picks up and companies work to rebuild. Employers use temporary workers as a resource because (6) offer
flexibility and come at a low cost. Many temporaries are categorized as "independent contractors" instead of employees, (7) allows the employer to avoid (8) certain taxes. Because they are not required to offer benefits to temporary workers, companies can save a great deal of money by hiring temps. Usually, temporary workers can qualify (9) benefits if they work for a staffing company for a certain length of time. Most temps, however, do not continue with one company long (10) to qualify for them because they regard the position as a step on the ladder to a (11) position later.
According to Richard Wahlquist, president of the American Staffing Association, 75 (12) of temporary workers hope for transition out of the temporary staffing category (13) a period of time. Wahlquist finds that temporary workers spend about 11 weeks on various assignments before their (14) out of the temporary workforce. Many use temporary positions to gain experience and skills (15) they move on to better jobs. Wahquist says that the temp workforce as a whole turns (16) 400 percent each year.
Tom Dilworth, research director at the Employment Policies Institute, explains (17) some workers like having temporary jobs (18) it affords them a great deal of elasticity with time and everything. Some temps only have a limited (19) of time to work and temp agencies can help coordinate jobs to fit their schedules. Other sometimes-employees use temporary jobs to get an (20) to a company from the inside, to get a foot in the door of a certain business or career. (21) others take temporary positions in hopes their employers will change them over to permanent positions eventually.
Nearly all the industries in the United States use temporary workers. (22) to Tim Costello, coordinator of the North American Alliance for Fair Employment, the growth of temporary labor threatens (23) job security of permanent workers who fear replacement,as well as the temps who are more accustomed to turnover. He predicts that there will continueto (24) a gradual shift from permanent employees to contingent staffing, and that such a (25) in workplace demographics will "lead to lower wages, poorer working conditions, and more instability."

查看答案