问题 单项选择题

In 1998 consumers could purchase virtually anything over the Internet. Books, compact discs, and even stocks were (1) from World Wide Websites that seemed to (2) almost daily a few years earlier, some people had predicted that consuners accustomed to shopping in stores would be (3) to buy things that they could not see or touch (4) . For a growing number of time-starved consumers, however, shopping from their home computer was proving to be a convenient (5) to driving to the store.

A research estimated that in 1998 US consumers could purchase $ 7.3 billion of goods over the Internet, double the 1997 total. Finding a bargain was getting easier, (6) the rise of online auctions and Websites that did comparison shopping on the Internet for the best (7) .

For all the consumer interest, (8) in eyberspaee was still a largely (9) business, however. Internet pioneer Amazon. eom, which began selling books in 1995 and later (10) into recorded music and videos, posted (11) of $ 153.7 million in the third quarter, up from $ 37.9 million in the same period of 1997. Overall, (12) , the company’ s loss widened to $ 45.2 million from $9.6 million, and analysts did not expect the company to turn a profit (13) 2001. (14) the great loss, Amazon. tom had a stock market value of many billions, reflecting investors’ (15) about the future of the industry.

Internet retailing appealed (16) investors because it provided an efficient means for reaching millions of consumers without having the cost of operating (17) stores with their armies of salespeople. Selling online carried its own risks, however, (18) so many companies competing tor consumers’ attention, price competition was (19) and profit (20) thin or nonexistent.

18()

A.for

B.despite

C.to

D.with

答案

参考答案:D

解析:

[测试点] 词语的用法

[解题思路] 介词with可以表示原因,翻译成“因为”。介词for表原因的话,常放在句末,如放在句首,常表示目的。

填空题
实验题

(1) 利用下列反应可以将粗镍转化为纯度达99.9%的高纯镍。

Ni(s)+4CO(g) Ni(CO)4(g) 该反应的ΔH_________0 (选填“>”或“=”或“<”)。

(2) 在高温下一氧化碳可将二氧化硫还原为单质硫。已知:

C(s)+O2(g)=CO2(g)          ΔH1=-393.5 kJ·mol-1

CO2(g)+C(s)=2CO(g)        ΔH2=+ 172.5 kJ·mol-1

S(s)+O2(g)=SO2(g)          ΔH3=-296. 0 kJ·mol-1

请写出CO除SO2的热 化学方程式__________。

(3) 已知Na2CrO4溶液酸化时发生的反应为:2CrO42-+2H Cr2O72-+H2O,若1L酸化后所得溶液中铬元素的总 物质的量为0.55 mol,CrO42-有10/11转化为Cr2O72-。又知:常温时该反应的平衡常数K=1014。求上述酸化后所得溶 液的pH_________。

(4) 根据有关国家标准,含CrO42-的废水要经化学处理,使其浓度降至5.0×10-7 mol·L-1以下才能排放。含CrO42-的废水处理通常有以下两种方法。

① 沉淀法:加入可溶性钡盐生成BaCrO4沉淀[Ksp(BaCrO4)=1.2×10-10],再加入可溶性硫酸盐处理多余的Ba2+。加入可溶性钡盐后的废水中Ba2+的浓度应不小于_________mol·L-1,然后再进行后续 处理方能达到国家排放 标准。若原废水中CrO42-浓度为a mol/L,请在图中画出c(CrO42-)与c(Ba2+)的关系图,并进行必要的标注。

② 还原法:CrO42-Cr3+Cr(OH)3。用该方法处理10 m3 CrO42-的物质的量浓度为1.0×10-3 mol·L-1的废水,至少需要绿矾(FeSO4·7H2O,相对分子质量为278)__________Kg(保留两位小数)。