问题 问答题

利用下列所示仪器、药品(及其它必要物品)设计制取氧气和试验其性质的实验对比方案.

(1)对比加入试剂顺序对于制取氧气影响

方法一:把二氧化锰加入装有过氧化氢溶液的试管中

方法二:把过氧化氢溶液缓缓加入盛有少量二氧化锰的试管中

结论:
(2)对比不同反应物制取氧气反应速率

反应物药品的名称化学方程式选用反应装置的仪器名称
过氧化氢溶液、二氧化锰
氯酸钾、二氧化锰
结论:
(3)对比硫在空气里与在氧气中燃烧的现象

实验名称操作步骤实验现象
硫在空气里燃烧
硫在氧气中燃烧
结论:

答案

(1)二氧化锰是过氧化氢反应的催化剂,方法一中二氧化锰与大量过氧化氢混合,迅速生成大量氧气,方法二中反应比较平稳,能得到平稳的氧气流;

故答案为:结论:要得到平稳的氧气流,需将过氧化氢缓缓加入二氧化锰中;

(2)过氧化氢与二氧化锰混合生成水和氧气,不需加热,所以反应装置选取具支试管、铁架台、注射器,方程式是2H2O2

 MnO2 
.
 
2H2O+O2↑;氯酸钾与二氧化锰混合加热生成氧气和氯化钾,需加热,所以反应装置选取试管、单孔塞、铁架台、酒精灯,方程式是2KClO3
MnO2
.
2KCl+3O2↑;氯酸钾与二氧化锰混合加热制取氧气,用时间多;而过氧化氢溶液和二氧化锰混合后即可产生氧气,反应速率快;

故答案为:

反应物药品的名称化学方程式选用反应装置的仪器名称
过氧化氢溶液、二氧化锰2H2O2
 MnO2 
.
 
2H2O+O2
具支试管、铁架台、注射器
氯酸钾、二氧化锰2KClO3
MnO2
.
2KCl+3O2
试管、单孔塞、铁架台、酒精灯
结论:过氧化氢溶液和二氧化锰混合后即可产生氧气,反应速率快
(3)对比硫在空气里与在氧气中燃烧的现象:将硫放于燃烧匙,在酒精灯上点燃,观察到硫在空气中燃烧发出微弱的淡蓝色火焰,放出热量,生成有刺激性气味的气体;将硫点燃放于氧气瓶中,观察到硫在氧气中燃烧发出明亮的蓝紫色火焰,放出热量,生成有刺激性气味的气体,由此可知氧气的浓度越大可燃物燃烧越剧烈;

故答案为:

实验名称操作步骤实验现象
硫在空气里燃烧将硫放于燃烧匙,在酒精灯上点燃发出微弱的淡蓝色火焰,放出热量,生成有刺激性气味的气体
硫在氧气中燃烧将硫点燃放于氧气瓶中发出明亮的蓝紫色火焰,放出热量,生成有刺激性气味的气体
结论:氧气的浓度越大可燃物燃烧越剧烈

阅读理解

The Pentagon(五角大楼), headquarters of the Department of Defense in US, is one of the world's largest office buildings. It is twice the size of the Merchandise Mart in Chicago, and has three times the floor space of the Empire State Building in New York. There are very few people throughout the United States who do not have some knowledge of the Pentagon. Many have followed news stories coming from this building. However, relatively few people have had the chance to visit it.

The Pentagon is in fact a city in itself. About 23,000 employees, both soldiers and other people, contribute to the planning of the defense of the country. These people arrive daily from Washington, D.C. and around over about 30 miles of highways, including express bus lanes(快车道) and one of the newest subway system in the country. They ride past 200 acres of grass land to park about 8,770 cars in 16 parking lots; climb 131 stairways or take 19 lifts to reach offices that occupy 3,705 square feet. While in the building, they tell time by 4,200 clocks, drink from 691 water taps, make use of 284 rest rooms, use up 4,500 cups of coffee, 1,700 pints of milk and 6,800 soft drinks prepared or served by a restaurant of 230 persons and distributed(分散于) in 1 dining room, 2 cafeterias, a snack bars, and an outdoor snack bar.

The building itself is an extraordinary structure. Built during the early years of World War II, it is still thought of as one of the most efficient buildings in the world. In spite of 17.5 miles of corridors(走廊) it takes only seven minutes to walk between any two points in the building.

60. Which of the following statements about the Pentagon is true?

A. Most Americans know about it.                    

B. It is now open to the public.

C. Around 23,000 workers contribute to its planning. 

D. It is one of the world's tallest buildings.

61. Which of the following statements about the transportation of the Pentagon is NOT true?

A. It is easy to reach by subway.                    B. People can drive directly to it.

C. People can go there by bus.                           D. The parking lots cover 200 acres of land.

62. Why did the author write so many numbers in the second paragraph?

A. To show that he knew quite a lot about the Pentagon.

B. To show the vast size of the Pentagon.

C. To show it costs a lot of money to keep the Pentagon going.

D. To show that the Pentagon is a convenient place.

63. What do you know about the structure of the Pentagon?

A. All the offices are connected by the newest subway system.

B. The longest distance between two offices is 17.5 miles.

C. It takes no more than 7 minutes to walk from one place to another.

D. There are neither rest rooms nor snack bars in it.

单项选择题