问题 选择题

水热法制备纳米颗粒Y(化合物)的反应为:3Fe2+2S2O32-+O2+4OH=Y+S4O62-+2H2O,下列有关说法正确的是

A.Y的化学式为Fe2O3

B.S4O62- 是还原产物

C.被1mol O2氧化的Fe2物质的量为1 mol

D.每 32 gO2参加反应,转移电子的物质的量为4 mol

答案

答案:D

题目分析:根据质量守恒可知,Y为化合物,反应前后的原子个数相等,则Y为Fe3O4,故A错误。S2O32-中S的价态是+2价,S4O62-中S的价态是+2.5价,故S4O62- 是氧化产物,B项错误。反应中转的电子总数等于氧元素化合价降低的数目,氧气中的氧元素全部从0价降到-2价,共得到1mol×2×(2-0)=4mol电子,故D正确。

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.

1()

A.assessable

B.available

C.acceptable

D.abundant

多项选择题