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[化學 Chem] Summer Holiday Assignment



Summer Holiday Assignment

[隱藏]
1. Guess what alkane the following mass spectrum represents.
A Good Analyzer Must Be A Good Collector.

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2. For the following endothermic forward reaction:



(a) Why the equilibrium constant increases when more heat is supplied?
(b) Why the equilibrium constant decreases when the pressure increases?

You should give a stoichiometric account apart from applying Le Chatelier's principle

[ 本帖最後由 doraemonserv 於 2018-7-6 04:26 AM 編輯 ]






A Good Analyzer Must Be A Good Collector.

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3. Given the structure of a salt:

Derive the empirical formulae for this salt containing the following atoms:

引用:
K: 26.8%
Fe: 12.8%
C: 16.5%
O: 43.9%


Given the relative atomic masses:

引用:
K: 39.1
Fe: 55.8
C: 12
O: 16




A Good Analyzer Must Be A Good Collector.

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4. You are going to do online research to find a method to determine the mass of BaO and BaO2 in a solid mixture of both 2 compounds.

Hints:

引用:
1. Both of them can react with H2SO4. BaO will produce H2O and BaO2 will produce H2O2
2. KI can react with H2O2 to give I2.






A Good Analyzer Must Be A Good Collector.

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[隱藏]
Hints

1. The molar mass of C_n-H_(2n+2) = 170

2. Pressure flows from area of more molecules to area of less molecules

3. The structure:


4. We use the mole ratio by back titration to predict the actual mass.
A Good Analyzer Must Be A Good Collector.

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我可唔可以八掛下你D題目係邊到搵出來?
我時光倒流返A𠃊 全盛時期,我都不會全部。






究竟我們人類 (或至少 uwant 的網友),是否沒有能力在 不標懺化或侮辱他人的情況下理性地討論?
-----
小的可是唯物科學懷疑實證論存在主義者。

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我依家成日幻想10年後考DSE?
想問下 phy chem bio  自修生係米要考 實驗?






究竟我們人類 (或至少 uwant 的網友),是否沒有能力在 不標懺化或侮辱他人的情況下理性地討論?
-----
小的可是唯物科學懷疑實證論存在主義者。

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回覆 6#  sealion 的帖子

From Question Banks.

I am a collector.




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回覆 7#  sealion 的帖子

Of course in DSE all science subjects (Home Economics, DT, Phy, Chem, Bio, IS) require lab works, otherwise mainland candidates can seize freshman seats easily.

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[隱藏]
引用:
1. Guess what alkane the following mass spectrum represents.


用16+(n-1)*14呢條式就搵到個成份
2碳、3碳、4碳、5碳、6碳、7碳、8碳、9碳、10碳、12碳 都有
2碳、3碳、4碳、5碳、6碳係主要成份

引用:
(a) Why the equilibrium constant increases when more heat is supplied?
(b) Why the equilibrium constant decreases when the pressure increases?

You should give a stoichiometric account apart from applying Le Chatelier's principle


a) 反應個 ∆H>0 --> endothermic reaction --> heat increase--> shift to right --> Keq increase
b) ∆n > 0 --> pressure increases --> shift to left --> Keq decrease

引用:
3. Given the structure of a salt:

Let there are a K, b Fe and c C2O4

39.1a : 55.8b : 88c = 0.268 : 0.128 : 0.604

If c =1
39.1*1 : 55.8*1/3 : 88*1  = 0.268 : 0.128 : 0.604
So a:b:c= 3:1:3
K3Fe(C2O4)3

引用:
4. You are going to do online research to find a method to determine the mass of BaO and BaO2 in a solid mixture of both 2 compounds.



H2SO4 + BaO --> BaSO4 + H2O
H2SO4 + BaO2 --> BaSO4 + H2O2
H2O2 + 2KI --> I2 + 2KOH知道可以用幾多 KI 生成 I2,就知道生成左幾多 H2O2,咁就找到 BaO2 個 mass,餘下就係 BaO

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回覆 10#  ledahdeath 的帖子



16+(n-1)*14 = 170

n = 12



You get all correct!

Have you obtained an A in AL Chem?

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