问题 选择题

下列实验“操作和现象”与“结论”对应关系正确的是(  )

 操作和现象结论
A向装有Fe(NO3)2溶液的试管中加入稀硫酸,在管口观察到红棕色气体HNO3分解成了NO2
B向淀粉溶液中加入质量分数为20%的硫酸,加热几分钟,冷却后再加入新制Cu(OH)2浊液,加热,没有红色沉淀生成淀粉没有水解成葡萄糖
C甲烷和氯气混合后在光照下,颜色逐渐褪去甲烷和氯气发生了化合反应
D向饱和Na2CO3中通入足量CO2,溶液变浑浊析出了NaHCO3
 

答案

答案:D

A项,硝酸根在氢离子存在下表现强氧化性将二价铁离子氧化,硝酸根被还原为NO,NO又被空气中的氧气氧化为二氧化氮,A错误;B项,没有红色沉淀生成也可能是因为冷却后没有加入碱中和过量的稀硫酸,B错误;C项,甲烷和氯气发生取代反应,C错误;D项正确。

单项选择题
单项选择题

A narrowing of your work interests is implied in almost any transition from a study environment to managerial or professional work. In the humanities and social sciences you will at best reuse only a fraction of the material (1) in three or four years’ study. In most career paths academic knowledge only (2) a background to much more applied decision-making. Even with a " training " form of degree, (3) a few of the procedures or methods (4) in your studies are likely to be continuously relevant in your work. Partly this (5) the greater specialization of most work tasks compared (6) studying. Many graduates are not (7) with the variety involved in (8) from degree study in at least four or five subjects a year to very standardized job (9) . Academic work values (10) inventiveness, originality, and the cultivation of self-realization and self-development. Emphasis is placed (11) generating new ideas and knowledge, assembling (12) information to make a " rational " decision, appreciating basic (13) and theories, and getting involved in fundamental controversies and debates. The humanistic values of higher (14) encourages the feeling of being (15) in a process with a self-developmental rhythm. (16) , even if your employers pursue enlightened personnel development (17) and invest heavily in " human capital " —for example, by rotating graduate trainees to (18) their work experiences—you are still likely to notice and feel (19) about some major restrictions of your (20) and activities compared with a study environment.

6()

A.with

B.against

C.upon

D.from