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（7分）实验室常用一定质量分数的过氧化氢无色溶液（溶质为H2O2），在二氧化锰作催化剂的条件来制取氧气。某同学实验前测得过氧化氢溶液42.5g，加入1 g MnO2，完全反应后测得反应容器中剩余物质量为41.9g。 请回答：

（1）实验室用分解双氧水的方法制取氧气时，选择的发生装置应为_________。

（2）收集装置应选择_________，原因是____________________________________。

（3）反应后放出氧气的质量是多少，所用过氧化氢溶液中溶质的质量分数是多少？

[计算结果保留一位小数，计算过程按步骤写在答卷纸上]

答案

（1）  B 。（2）   C或D ， 氧气不易溶于水且比空气的密度大 。

（3）[计算结果保留一位小数，计算过程按步骤写在答卷纸上]

解：①m氧气=" 42.5g" +1g －41.9g="1.6g" ............................... 1分    

②设过氧化氢溶液中溶质的质量为X，则

2H2O2 ="=====" 2H2O + O2↑      .............................. 1分

68               32

X               1.6g

              ∴X =3.4g..................... 1分

∴过氧化氢溶液中溶质的质量分数="3.4g/42.5g" ×100%=8%  ......    1分

答：过氧化氢溶液中溶质的质量分数为8%

根据双氧水分解的反应原理及氧气的密度和溶解性确定发生和收集装置，并根据质量守恒定律判断氧气的质量，依据方程式和溶质的质量分数计算过氧化氢溶液中溶质的质量分数．

单项选择题

Passage Three

In the world of climate change, it is in the Earth’s Cold regions where trends can most easily be seen. The cryosphere, where water is found in solid form, is among the most sensitive regions to temperature change.
The sensitivity of ice and snow to temperature changes is an early indicator of even relatively small differences, says University of Colorado at Boulder senior researcher Richard Armp. He has found that today’s receding and thinning sea ice, mountain glacier mass losses, decreasing snow extent, melting permafrost (永久冻土), and rising sea level are all consistent with warming.
Global mean temperatures have risen one degree Fahrenheit over the past 100 years, with more than half of the increase occurring in the last 25 years, observes Armp who is affiliated with the National Snow and Ice Data Center headquartered at CU-Boulder.
"As slight as that may seem, it’s enough to make a difference," said Armp. "Now, long-term monitoring of a series of cold region, or cryospheric, parameters (参数) shows that for several decades the amounts of snow and ice around the world have been decreasing. "
The extent of Arctic sea ice is shrinking by about 3 percent per decade, but the trends are not uniform. While recent studies have indicated that the ice thickness also had decreased over several decades, new information shows that the ice may have thinned rapidly, Armp said. Examination of springtime ice thickness in the Arctic Ocean indicates that the mean ice thickness decreased 1.5 meters (4. 8 feet) between the mid-1980s and early 1990s.
To mark its 25th anniversary, the National Snow and Ice Data Center has organized a special session at the 2001 Fall Meeting of American Geophysical Union, taking place this week in San Francisco, that illuminates overall changes in the cryosphere.
The session begins Tuesday and extends through Thursday afternoon, with 75 contributions from all areas of cryospheric study. Papers and posters include examinations of lake and river ice, glacier dynamics, and mass ice balance studies in polar and continental glaciers, regional and polar snow cover trends, and variations in Canadian ice cap elevations.

The signs of global warming include all of the following EXCEPT ______ .

A．thinning sea ice

B．decreasing snow extent

C．melting permafrost

D．falling sea level
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单项选择题

仪表板上安装各种仪表对汽车的动态作出判断，其中水温表在正常工作时指针应在（）之间。

A.60℃-70℃

B.70℃-80℃

C.80℃-90℃

D.90℃-100℃
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