回應1
kino watashi:
Thanks~~
1. 我想問下, 為甚麼PVC 可以store concentrated sulphuric acid??? 聽說他們是有reaction 的.假設你mc 10 的答案對了, 為甚麼ethyl ethanoate 不可以store 在 expanded polystyrene container 呢?
2. mc 30 為甚麼第二條statement 不是第一條的正確解釋呢????
請賜教!!~~
化學友:
1. kino watashi，ethyl ethanoate係organic solvent，expanded polystyrene係會dissolve o向ethyl ethanoate。如果有機會，你可以試試將ethyl ethanoate加入expanded polystyrene cup，幾minutes後ethyl ethanoate變成白色，因為polystyrene dissolve左入去ethyl ethanoate到。
至於PVC係inert towards many chemicals例如conc. H2SO4。你可以睇睇2000 Paper II 38就明，PVC唔會同conc. H2SO4 react，佢只會soften at high temp。
2. Carbon can form a large number of compounds with long carbon chains嘅原因係因為C-C bond strong而唔係因為carbon atoms can share elctrons with one another。好多elements(例如Si)都可以share electrons with one another，但係就唔會form compounds with long Si chains因為Si-Si bond好弱。OK ma kino watashi?
回應2
Simon:
可唔可以解釋一下 07 chem mc 既第 5,26,27,39,42同第47題 ? 同埋 .. 我想問 .. mc 幾多分先肯定有Ｃ？萬分感激！！
化學友:
Simon，sorry ar，e排都係好忙，d mc遲一排再答你丫。
其實，如果有35條correct就一定有C o架啦，唔使太擔心。
回應3
wk:
你可否評論一下今年Alevel Chem 係深定淺?通常ALEVEL Chem 合格係幾多分?
化學友:
化學友覺得Paper I幾深呀，要考生對chem嘅concept好clear先答得到。Paper II就OK la，都應該可以得到一定分數。
wk，通常ALEVEL Chem有80分(out of 200分)就一定合格o架啦。
回應4
小白:
你好，我之前有問過你問題的，不知道你記不記得。之前上網對了是錯8題，對了你那個是錯了10題。可以解釋下那些問題的答案嗎？4,10*,21,30,31,33,36,38,41,51= ="另外，如果MC錯10題，長題目錯唔超過20分，有冇c = =?我連合格都唔肯定..錯好多....愈對先知愈多錯，一開始睇仲以為岩。
化學友:
化學友更係記得你啦。唔好意思呀，同Simon一樣化學友遲d再答你d mc丫。
小白，其實如果你真係得到e o個分就100%有C或以上，唔使驚呀。仲有呀小白，唔好再對啦，越對得多就會越發覺多錯o架啦，會影o向心情同埋跟住嘅subject嘅performance。相信化學友啦，你chem ok o架啦。
7 則留言:
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+2
still, 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
--------------------------------
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?????
化學友:
感謝啦~~~
ethyl ethanoate 既是solvent又是solvent? 我還是第一次聽(學校的老師沒有說過)
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~~
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。
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??
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？
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.
張貼留言