在3%的H2O2溶液中，氢元素的质量分数为______，当H2O2制取氧气完全分_爱下问搜题

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问题问答题

在3%的H₂O₂溶液中，氢元素的质量分数为______，当H₂O₂制取氧气完全分解后，液体中氢元素的质量分数增加______%．（保留到小数点后l位）

答案

设过氧化氢溶液的总质量为100g，则双氧水（H₂O₂）为×3%=3g，水（H₂O）100g-3g=为97g，

∴溶液中氢元素的质量为：3g×

2

34

×100%+97g×

2

18

×100%=10.98g

∴溶液中氢元素的质量分数为

10.98g

100g

×100%=10.98%≈11.0%；

设3克过氧化氢分解生成O₂质量为x，

2H₂O₂

MnO2

.

2H₂O+O₂↑

68 32

3g x

68

3g

=

32

x

解之得：x≈1.41g

10.98g

100g-1.41g

×100%≈11.1%，

∴液体中的氢元素的质量分数增加11.1%-11.0%=0.1%．

故答案为：11.0%；0.1

解答题

一种演唱会门票原价80元/张，演出开始后降到60元/张．一个售票窗口共卖出这种门票180张，收入13800元．演出开始后卖出门票多少张？

完形填空

完形填空。（共20小题；每小题1分，满分20分）
阅读下面短文，从短文后所给各题的四个选项（A，B，C，D ）中选出可以填入空白处的最佳选项，并在答题卡上将该项涂黑。
When I was in primary school，I got into a major argument with a boy in my class. I can't 36 what it was about，but I have never forgotten the 37 I learned that day.
I was 38 that I was right and he was wrong－and he was sure that I was wrong and he was right. The 39 decided to teach us a very important lesson. She __40__ both of us up to the __41__ of the class and placed him on one side of her 42 and me on the other. In the 43 of her desk was a large，round object. I could __44__ see that it was black. She asked the boy what __45__ the object was.“White，”he answered.
I couldn't believe he said the object was white, __46__ it was obviously black！Another __47__ started between my classmate and me，this __48__ about the color of the object.
The teacher told me to go stand where the boy was standing and told him to come stand where I had been. We changed __49__，and now she asked me what the color of the object was. I __50__ answer，“White.”It was an object with two __51__ colored sides，and from his side it was white.__52__ from my side was it black.
My teacher taught me a very important lesson that day：You must __53__ in the other person's shoes and look at the __54__ through their eyes in order to __55__ understand their view.

B．fortunately

C．conversation

B．was able to

B．differently

C．beautifully

D．surprisingly

A．unexpectedly