STPM 化学问题 马拉松！

幸福蛋糕

我还是不明白...他本身是吸热,为什么加热他还会SHIFT TO RIGHT??

ForeSight

在一个endothermic reaction,
左边的substances 需要热能(吸热)才能react 来制造右边的products.
当你加热（提供Heat) 的时候，越来越多的substance会react 来制造products.
Substances 越来越少，Products越来越多，
所以Equilibrium Position will shift to the right.


p/s 如果我的解释有错误的话，请纠正我谢谢 。

darksider

( A , 5 dm^3 , P atm) -------|--------- ( B , 10dm^3 , 3atm)
The diagram above shows two bulbs containing gas A and gas B respectively at room temperature. When the | is removed and the system is allowed to attain equilibrium, what is the initial pressure of gas A when the final pressure is 5 atm?

螺丝猫

原帖由 darksider 于 15-6-2008 12:38 PM 发表
( A , 5 dm^3 , P atm) -------|--------- ( B , 10dm^3 , 3atm)
The diagram above shows two bulbs containing gas A and gas B respectively at room temperature. When the | is removed and the system is all ...

partial fraction of gas A=5/(5+10)
                                        =1/3
by using Dalton Law of partial pressure:
PA=(mole fraction of A)X PTotal
      =(1/3)X(5atm)
    =5/3 atm

螺丝猫

sodium and aluminium react aith chlorine to prodice sodium chloride and aluminium chloride respectively.which of the  compounds has higher boiling point.Explain your answer.

darksider

原帖由 螺丝猫 于 2008/6/15 01:15 PM 发表

partial fraction of gas A=5/(5+10)
                                        =1/3
by using Dalton Law of partial pressure:
PA=(mole fraction of A)X PTotal
      =(1/3)X(5atm)
    =5/3 atm

But the answer given by the book is 9 atm.This question is actually an objective question that has 4 choices.
A - 3atm B - 6 atm C - 9 atm D - 12 atm. I have got the same answer as yours but this is not the answer.
Is there any flaw in this question?

螺丝猫

那我把问题抄下来，去学校问老师。。。
I will write down the question and ask my teacher...
i will give the answer tomorrow...

秋分

原帖由 螺丝猫 于 15-6-2008 01:22 PM 发表
sodium and aluminium react aith chlorine to prodice sodium chloride and aluminium chloride respectively.which of the  compounds has higher boiling point.Explain your answer.

NaCl.bond between Na with Cl r ionic,thus they have higher boiling point...
补充一下,bong between Al with Cl r covalent,althought covalent bong between Al n Cl r~with ionic bond,bt high energy is required to break the bond between Al n Cl,nt the weak Van der waals forces between AlCl3 with another AlCl3...

秋分

原帖由 darksider 于 15-6-2008 02:09 PM 发表


But the answer given by the book is 9 atm.This question is actually an objective question that has 4 choices.
A - 3atm B - 6 atm C - 9 atm D - 12 atm. I have got the same answer as yours but this ...

想先,现在没空,等一下继续...

[ 本帖最后由 秋分 于 15-6-2008 06:41 PM 编辑 ]

秋分

原帖由 darksider 于 15-6-2008 02:09 PM 发表


But the answer given by the book is 9 atm.This question is actually an objective question that has 4 choices.
A - 3atm B - 6 atm C - 9 atm D - 12 atm. I have got the same answer as yours but this ...

答案对的...

秋分

原帖由 darksider 于 15-6-2008 12:38 PM 发表
( A , 5 dm^3 , P atm) -------|--------- ( B , 10dm^3 , 3atm)
The diagram above shows two bulbs containing gas A and gas B respectively at room temperature. When the | is removed and the system is all ...

p1v1=p2v2       p3v3=p4v4
10(3)=15(a)      5(p)=15(b)
a=2atm             a+b=5,thus b is 3
.
.
5p=45,
p=9atm

秋分

原帖由 ForeSight 于 15-6-2008 09:00 AM 发表
在一个endothermic reaction,
左边的substances 需要热能(吸热)才能react 来制造右边的products.
当你加热（提供Heat) 的时候，越来越多的substance会react 来制造products.
Substances 越来越少，Products越来越 ...

基本上是没措,chemical equilibria 在Le chatelier's principle 是...
if a changes is made to a system in equilibrium,the system reacts in such a way as tend to oppose the change,and a new equilibrium is formed

darksider

原帖由 秋分 于 2008/6/15 10:10 PM 发表

p1v1=p2v2       p3v3=p4v4
10(3)=15(a)      5(p)=15(b)
a=2atm             a+b=5,thus b is 3
.
.
5p=45,
p=9atm

Thanks!

螺丝猫

Explain the term  disprportionation.You may use an example to explain your answer.

morphv02c01

A disproportionation reaction is one in which a single substance is both oxidised and reduced.

2NaOH + Cl2 -----> NaCl + NaClO + H2O

Cl2 has a oxidation state of 0
After the reaction, Cl's oxidation state in NaCl is -1 (reduction), and the Cl in NaClO has an oxidation state of +1 (oxidation). Hence we can say that Cl2  has undergo disproportionation.

螺丝猫

请不要只回答问题。。。
在回答后把另一个问题放上来。。。
谢谢合作。。。

螺丝猫

请问要怎样看一个reaction的feasibility?我不是很会看？

秋分

原帖由 螺丝猫 于 23-6-2008 05:49 PM 发表
请问要怎样看一个reaction的feasibility?我不是很会看？

我是去年的考生,所以我只会回答,不会post题目上来了...
feasible是只有没有可能发生,看 E not/standard electrode potential的...

morphv02c01

顶一下。每人做化学吗？？

相思豆豆

原帖由 螺丝猫 于 23-6-2008 05:49 PM 发表
请问要怎样看一个reaction的feasibility?我不是很会看？

就是看reaction有没有可能occur，要看standard electrod potential (E) , +ve 的就有可能有reaction , 不过还要看它的activation engergy,
如果(E) +ve ，但是activation energy高，也就不可能发生reaction。。

我也是mcc，有错请指教。。。