问题 实验题

氮化铁磁粉是一种磁记录材料,利用氨气在400℃以上分解,将分解的氮原子渗透到铁粉中制备氮化铁。下面是制备氮化铁的步骤:

(1)制备单质铁某赤铁矿石含60. 0% Fe2O3、3.6% FeO,还含有Al2O3、MnO2、CuO等。某化学探究小组设计了如下实验流程

部分阳离子以氢氧化物形式完全沉淀时溶液的pH

步骤②中加双氧水的目的是_____________,pH控制在3.4的作用是___________,滤液b 中含有的金属阳离子是_________。步骤④中碾碎的目的是________________。

(2)制备氮化铁磁粉的反应:Fe+NH3FexNy+ H2(未配平),若消耗氨气34.0 g,消耗赤铁矿石

2 kg,则FexNy磁粉的化学式为___________。

答案

(1)使溶液中的Fe2+氧化为Fe3+;使溶液中的Fe3+完全沉淀,而其他金属离子不沉淀;Cu2+、Al3+;增大接触面积

(2)Fe16N2或Fe8N

单项选择题

A good modern newspaper is an extraordinary piece of reading. It is remarkable first for what it contains the range of news from local crime to international politics, from sports to business to fashion to science, and the range of comment and special features (特定) as well, from editorial page to feature articles and interviews to criticism of books, art, theatre and music. A newspaper is even more remarkable for the way one reads it never completely, never straight through, but always by jumping from here to there, in and out glancing at one piece, reading another article all the way through, reading just a few paragraphs of the next.

A good modern newspaper offers a variety to attract many different readers, but far more than any one reader is interested in. What brings this variety together in one place is its topicality (时事性), its immediate relation to what is happening in your world and your locality now. But immediacy and the speed of production that goes with it mean also that much of what appears in a newspaper has no more than transient (短暂的) value.

For all these reasons, no two people really read the same paper: what each person does is to put together out of the pages of that day’s paper, his own selection and sequence, his own news paper. For all these reasons, reading newspapers efficiently, which means getting what you want from them without missing things you need but without wasting time, demands skill and self-awareness as you modify and apply the techniques of reading.

According to the passage, the reason why no two people really read the same newspaper is that ().

A. people scan for the news they are interested in

B. different people prefer different newspapers

C. people are rarely interested in the same kind of news

D. people have different views about what a good newspaper is

单项选择题 A1/A2型题