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Schoolbag:
有條題我想問xIO3- +　yI- +　6H+ ----->_I2 + _H2O

ANSWER:X=1 Y=5

我想知Ｙ可吳可以系３？點解？

化學友:
schoolbag，化學友唸你當Y=3時，以為條equation係IO3- + 3I- + 6H+ --> 2I2 + 3H2O。

其實你睇漏左d o野啦，euqation除左elements要balance， charge都要balance。如果Y = 3，條equation d charge左右唔balance，左面係-2而右面係0，所以唔得呀。明白嗎?

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小白:
多謝你既提醒，我還是複習一下數學吧。因為之前一直都是溫化學物理(其他碰到沒碰)。多謝你肯熱心解答，謝謝。因為我一直都猶疑如果中六是選物理還是選化學好= =

其實中六的化學真的能夠解釋到我們不明白的嗎？即是有些問題老師總是說中六才會教，我怕到時又變成中七才會教，中七問時便是大學才會學。從小學到中學一直都是這樣，有極多問題都是不斷推遲說遲些教，不斷累加心中的疑問，真是非常辛苦。我都沒再對了，因為我本來化學成績就不好，只是臨考前溫了清了一點concept而已。所以能夠合格已經心足了。

化學友:
小白，化學友好明白你嘅疑問(講真，化學友讀F4時都有你嘅唸法)，e d o野非三言兩語講得完。咁啦，你會考後有時間化學友再同你慢慢discuss o下啦。

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kino_watashi:
1. 謝謝你的答覆雖然不是很明白你說甚麼但是我在yahoo!知識就找到了關於C-C這樣的一個回覆:True.formation of various (organic) compound is of due to the effective sharing of electron giving a stable covalent bond.(for your reference)the uniqueness of formation long carbon compound is called catenation.this is due to the effective sp3-sp3 sigma overlap of hybrids in C-C and C-H bond, i.e. relative high bond strength and is quite inert to ordinary reaction. therefore, nearly infinitely long or even stable hydrocarbons with cyclic carbon skeleton is formed. chain hydrocarbon is generalized by a formula CnH2n+2still, unsaturated carbon chain can be formed since neighboouring sp2 carbons contributes to effective p-p pi overlap making its formation gives extra stability.compared with silicon(also in group IV), covalent radius of Si-Si is larger. electrostatic attraction between nucleus and bonding electrons are less stronger than that in C-C bond. this is verified by the fact that in Si-Si, sigma overlap is less effective after hybridization. Si can only undergoes catenation up to 5 members

2.我想問下chem mc 42(3) 的amino acid formation 是不是out of syllabus 了?????
如果我chem 85%~90%對, mc 有45/50, 能不能有A?????

3. 我想問下, mc 47是C 而不是D 呢????因為我覺得only one variable 而其他都要the same, 所以我選了D.請指出我concept 上的錯誤, 謝謝~~

化學友:
1. kino_watashi，化學友覺得你chem嘅根底都好好。睇左你forward yahoo!知識段字，其實同化學友嘅explanation同一原理，不過因為e d係AL concept，所以未必睇得明。anyway o個ans係B o架啦。

2. 講真，kino_watashi e條有少少out c喇，因為我地CE多數學嘅monomer係有兩個一樣嘅functional groups，但其實兩個functional groups可以唔同，而都可以做到condensation polymer。e 條其實同CE 2005 條關於PLA 嘅long question一樣，都係有兩個唔同嘅functional groups。

如果你真係得到e o個分就一定A啦，恭喜你呀。

3. mc 47其實好難o架，會考後化學友先答你丫。 add oil la

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Tom:
HIHI~我第一次來的。我對近日教的chem有一些不明,希望你們幫幫手。在simple Cu-Ag cell中,為什麼不可以用CuSO4做electrolyte而要用AgSO4??

化學友:
Tom，CuSO4都可以做electrolyte o架，唔一定要AgSO4。

o向chemical cell裡面electrolyte係幫助conduct electricity，basically任何electroyte(e.g. NaCl)都可以用o向chemical cell裡面o架。只不過唔同electroyte會o向通電後係Ag electrode出唔同嘅products。

例如，
用CuSO4做electrolyte，Cu就會deposite o向Ag electrode

用AgSO4做electrolyte，Ag就會deposite o向Ag electrode

用NaCl做electrolyte，hydrogen gas就會o向Ag electrode evolve

至於點解有唔同 嘅products出，就要用electrochemical series先可以解到。化學友唸你阿sir/miss遲d會教o架啦。

Tom，如果仲有唔明，就留言比化學友啦。

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Eymon:
Dear Sir, one of my classmates said that in one year, only 92% or above correct can get an A in Chem, is it true? In fact, if I get 86% correct in 07 CE, to the best of your experience, do you think that I can get an A or not? Please tell me as soon as possible, since I am very worried and nervous.

化學友:
eymon, sorry呀，咁遲先答你。每一年CE chem mc大約45 out of 50就A，當然有時有例外啦，例如前兩年要o岩成47條先A。但係簡單o黎講每一年on average你mc岩45條long question有73-4分，overall就一定有A。如果你今年mc+long question平均有86%，咁就肯定有A o架啦(e排化學友聽到有d考生話今年分卷容易，要o岩好多先A。化學友肯定咁講一定唔係lor，其實好多考生都唔知自己錯左，以為白己o岩)。唔使worried呀eymon，比心機prepare好d a. maths呀，加油!!!