CHEMISTRY

purple_pig_33

4科当中有3科都有一定的把握了

只有chemistry最惨不忍睹==
我每次都fail的
因为我根本没读
而且也没有兴趣读
我只想要及格而已

如果只读physical和inorganic的
可以吗?
因为essay题通常都是两题physical两题inorganic

有经验的告诉我好吗?

我要去撞墙了

四月一日的小皮

lz没读organic chemistry吗？

darksider

Essay通常是
1) 3 physical , 1 inorganic , 2 organic
2) 2 physical , 2 inorganic, 2 organic

我建议你读organic。。。去上次我在biology贴里给的link下载chemistry factsheets...读读看，你可能会score到。

你的情况很危险。。。因为如果obj要拿40>，你的organic和physical要好。如果essay要拿高分，organic 也要好( structure 1, essay 2)和physical (structure 2 , essay 2/3).

其实chemistry并不难，只要有心去读就能了，但楼主似乎早已放弃对它的爱。。那么现在唯一的方法就是速读，然后速记。去下载那些chemsheets,会比你的课本好多。

idontwant2b

读organic也不错的，
一个道理，哪里都可以用。

structure通常mainly 2 physical 1 organic 1 inorganic
essay通常2physical, 2 inorganic, 2 organic，
明白一些道理就可以回答40分里中的很多分了。

Dicardo

爲什麽不讀organic呢？
organic essay一般上很容易那分。。。不用explain一大堆。。。

purple_pig_33

原帖由 四月一日的小皮 于 14-11-2009 08:14 PM 发表
lz没读organic chemistry吗？

應該說連動都沒動過

purple_pig_33

原帖由 darksider 于 14-11-2009 11:00 PM 发表
Essay通常是
1) 3 physical , 1 inorganic , 2 organic
2) 2 physical , 2 inorganic, 2 organic

我建议你读organic。。。去上次我在biology贴里给的link下载chemistry factsheets...读读看，你可能会score到。 ...

說真的
organic還真的沒動過
==
但是要記很多equation的不是

purple_pig_33

darksider
我開來看了
我想下載organic的就好
但是。。
我不懂哪個是organic的
==

darksider

原帖由 purple_pig_33 于 2009/11/15 02:02 PM 发表
darksider
我開來看了
我想下載organic的就好
但是。。
我不懂哪個是organic的
==

http://www.curriculum-press.co.uk/a-level/chemistry/factsheet_titles.htm
这里查。

891108

org很闷！
我上次只读phy+inor
C+

四月一日的小皮

我对chemistry的看法：
１）physical chem：
    concept+calculation，多chp但是很basic（看看大学的phy chem
    吧，+很多很多physic的东西）
２）inor chem：
    多equation要背，但chp很少，固然题目可以overlap（mean可
    以+phy chem一起出）（有些out of syllabus）
３）org chem：reagent和condition很重要+mechanism很有趣，
    chp和chp有overlap。但如过可以的话，mindmap很有帮助。
    poylmerisation那part（mechanism，condition，use）要很清
    楚。

check syllabus，有些part 是不重要的（like henry＇law）。


希望大家分享下吧。

darksider

看了很多参考书，他们都似乎不会解释inert pair effect,那我来解释好了。
Group 14 element 的 valence electronic configuration (ground state):
ns2 npx1 npy1 npz0 (画出来最好）

In excited state,
ns1 npx1 npy1 npz1

To form four covalent bonds, promotion of one electron from ns2 to npz0 is required and this requires energy. The required energy is compensated by the energy released from the extra 2 bonds formed.

However, going down the group 14, outer electrons are further from the nucleus, so the nuclear attraction towards the outer electrons is weaker. This causes the new bonds formed to be weaker (bond length increases, weaker nuclear attraction) and thus less energy is released which cannot compensate the energy required for promotion of electrons. So the two electrons in ns shell is unlikely to involve in bonding. This phenomenon is termed 'inert pair effect'.

Alcohol
----------
ROH + HX ----> RX + H2O
Condition : r.t
Mechanism: nucleophilic
Reaction type: substituition

ROH + PCl5 ---- > RCl + POCl3 + HCl (g) --- steamy white fumes of hcl is released (test)
condition : add PCl5 in dry conditions
mechanism : nucleophilic
reaction type : substituition

ROH + SOCl2 (thionyl chloride) ---- > RCl + SO2(g) + HCl(g)
condition : r.t
mechanism : nucleophilic
reaction type: substituition
*preferred over PCl5 because the side-products are gaseous.

Alcohol ---------(i)-----------> Carbonyl compound ---------(ii) ----------> carboxylic acid
(i) K2Cr2O7 (potassium dichromate (VI) oxide) dissolved in dilute H2SO4
(ii) same

Primary alcohol -------(i) ---------> aldehyde --------(ii) ------> carboxylic acid
Secondary alcohol ------(i)---------> ketone ---------X --------> carboxylic acid

X- under normal condition, ketone is stable to oxidation ; only by using very strong oxidising agent such as potassium manganate(VII) oxide under controlled condition, will it be oxidised.


Dehydration
----------------
Alcohol ------> alkene + H2O
condition : excess concentrated sulphuric acid at 170*C

Formation of ether
------------------------
Alcoho ------> ether + H2O
condition : excess concentrated sulphuric acid at 140*C

[ 本帖最后由 darksider 于 16-11-2009 01:51 PM 编辑 ]