STPM 化学问题 马拉松！

beautifuldays

原帖由 dunwan2tellu 于 26-10-2006 03:37 PM 发表
问题 68
Which of the following is/are true about electrolysis?

A.Reduction occurs at ahode .
B.Electron travels from cathode to anode in external cicuit.
C.The readiness of a cation to discha ...

A 的是什么。。。。ANODE还是CATHODE阿。。。
如果是CATHODE的话，那么。。。。答案就是A。

dunwan2tellu

原帖由 beautifuldays 于 26-10-2006 03:53 PM 发表


A 的是什么。。。。ANODE还是CATHODE阿。。。
如果是CATHODE的话，那么。。。。答案就是A。

不好意思，typing error . 我要打的是 anode 来的

lyt87

是D吗？？？？？？？？

哈贼

原帖由 dunwan2tellu 于 26-10-2006 03:37 PM 发表
问题 68
Which of the following is/are true about electrolysis?

A.Reduction occurs at anode .
B.Electron travels from cathode to anode in external cicuit.
C.The readiness of a cation to discha ...

答案是C吧！
higher the reactivity,lower the readiness for the ion 2 discharge.

下议题：
state 3 chemical properties and 3 physical properties of group 1 elements.

dunwan2tellu

原帖由 哈贼 于 26-10-2006 11:20 PM 发表


答案是C吧！
higher the reactivity,lower the readiness for the ion 2 discharge.

对了！

下议题：
state 3 chemical properties and 3 physical properties of group 1 elements.

Chemical Properties :
-react vigorously with water to form alkaline solution and evovled hygrogen gas.
-react vigorously with hydrochloride acid to gv salt and hygrogen gas
-react vigorously with oxygen gas to form oxide

Physical Properties:
-can conduct electricity in solid and molten state
-has relative low density compare to water(group 1 metal float on water)
-has relative low boiling point compare to other group metal

dunwan2tellu

问题 70
What chemical can be used to develope colourless amino acid spots obtained in a chromatogram ?

A.Ninhydrin
B.Acetic acid
C.Ethylene glycol
D.Acetone

hamilan911

原帖由 dunwan2tellu 于 27-10-2006 10:50 AM 发表
问题 70
What chemical can be used to develope colourless amino acid spots obtained in a chromatogram ?

A.Ninhydrin
B.Acetic acid
C.Ethylene glycol
D.Acetone

A.有解释吗？应该没有吧。。。
下一题有劳版主了，谢谢。。

dunwan2tellu

答对了！hamilan911 哈哈。为什么你每次都叫我代劳的?

问题 71

The partition coefficient between X and water is 10.If 4.0g of caffeiene is distributed between 100cm^3 of X and 200 cm^3 water,how much caffeine is dissolved in X ?

lyt87

答案是3.3g吗？？？？？

dunwan2tellu

原帖由 lyt87 于 27-10-2006 12:15 PM 发表
答案是3.3g吗？？？？？

答对了！2个significant figure （完全正确）
可以的话，在你的回帖中显示你的做法。谢谢

之后你就可以放下一题了

lyt87

let the mass of caffeine in X be x,

(concentration of caffeine in X/ concentration of caffeine in H2O) = 10
(x/100)/[(4-x)/200] = 10
...........
x=3.3g

lyt87

问题72


4g nitrogen gas and 2g helium gas are mixed in a 2.00 dm^3 enclosed vessel at 323K, what is the pressure (kPa) in the vessel?

[ 本帖最后由 lyt87 于 27-10-2006 12:47 PM 编辑 ]

dunwan2tellu

原帖由 lyt87 于 27-10-2006 12:44 PM 发表
问题72


4g nitrogen gas and 2g helium gas are mixed in a 2.00 dm^3 enclosed vessel at 323K, what is the pressure (kPa) in the vessel?

PV = nRT

no of mole of N2 = 4/28 = 1/7 mole
no of mole of He2 = 2/4 = 1/2 mole

ToTal pressure : P(N2) + P(He2) = RT/V * (mole of N2 + mole of He2)
                                = (8.31)(323)/2.00x10^-3 * (1/7 + 1/2)
                                = 863kPa

[ 本帖最后由 dunwan2tellu 于 27-10-2006 01:20 PM 编辑 ]

原帖由 ss_sky87 于 16-10-2006 02:21 发表


有啊．．．ｏｒｇａｎｉｃ的。
R-CHO 不是aldehyde麽？
如果沒記錯的話。

yes ar.
but C2H2 is ethnye which contains triple bond.

dunwan2tellu

问题 73

What are the advantages of using ether as an extraction solvent ?

1.Ether is chemically inert
2.Ether is not combustible
3.Ether is miscible with water

lyt87

答案是 1而已吗？？？？？？？

dunwan2tellu

原帖由 lyt87 于 30-10-2006 05:38 PM 发表
答案是 1而已吗？？？？？？？

是的。Ether is not miscible with water . Ether is flamable .下一题

banko

pls list out 3 type of solid desiccant...

哈贼

什么是desiccant?

banko

use to remove water...