问题 问答题

氯酸钾和二氧化锰的混合物共20g,加热完全反应后,冷却、称量,固体质量为15.2g,将固体全部倒入烧杯中,再加入92.55g水,搅拌、过滤,得不饱和溶液(二氧化锰不溶于水,操作过程中水分损失不计).

计算:①产生氧气的质量;

      ②所得不饱和溶液中溶质的质量分数.

答案

(1)二氧化锰为催化剂,反应前后其质量不变,根据质量守恒定律,产生氧气的质量为:20g-15.2g=4.8g;

(2)设反应中生成氯化钾的质量为x

2KClO3 

MnO2
.
2KCl+3O2

               149   96

                x    4.8g   

149
96
=
x
4.8g
  解得 x=7.45

溶液中溶质的质量分数为

7.45g
7.45g+92.55g
×100%=7.45%

答:①产生氧气的质量为4.8g;

    ②所得不饱和溶液中溶质的质量分数为7.45%.

材料分析题
单项选择题

"It is an evil influence on the youth of our country. " A politician condemning video gaming Actually, a clergyman denouncing rock and roll 50 years ago. But the sentiment could just as easily have been voiced by Hillary Clinton in the past few weeks, as she blamed video games for "a silent epidemic of media desensitisation" and "stealing the innocence of our children".

The gaming furore centers on "Grand Theft Auto: San Andreas", a popular and notoriously violent cops and robbers game that turned out to contain hidden sex scenes that could be unlocked using a patch downloaded from the internet. The resulting outcry (mostly from Democratic politicians playing to the centre) caused the game’s rating in America to be changed from "mature", which means you have to be 17 to buy it, to "adults only", which means you have to be 18, but also means that big retailers such as Wal-Mart will not stock it. As a result the game has been banned in Australia; and, this autumn, America’s Federal Trade Commission will investigate the complaints. That will give gaming’s opponents an opportunity to vent their wrath on the industry.

Skepticism of new media is a tradition with deep roots, going back at least as far as Socrates’ objections to written texts, outlined in Plato’s Phaedrus. Socrates worried that relying on written texts, rather than the oral tradition, would "create forgetfulness in the learners’ souls, because they will not use their memories; they will trust to the external written characters and not remember of themselves." (He also objected that a written version of a speech was no substitute for the ability to interrogate the speaker, since, when questioned, the text "always gives one unvarying answer". His objection, in short, was that books were not interactive. Perhaps Socrates would have thought more highly of video games. )

Novels were once considered too low-brow for university literature courses, but eventually the disapproving professors retired. Waltz music and dancing were condemned in the 19th century; all that twirling was thought to be "intoxicating" and "depraved", and the music was outlawed in some places. Today it is hard to imagine what the fuss was about. And rock and roll was thought to encourage violence, promiscuity and Satanism ; but today even grannies buy Coldplay albums.

We can learn from the text that human beings have a history of ()

A. fascination for the academic establishment

B. enthusiasm for juvenile psychology

C. disbelief in the novel medium

D. hatred of political corruption