chemistry既問題‥

小霞的fans

麻煩各位大大..我又開post了><""

fractional distillationseperates the petroleum into different groups of simpler mixture.the process does not result in the seperation of each substance in petroleum.

我想問紅字同藍字講既野有咩分別 -0- "" thx

An organic compound X has the molecular formula C3H4F2. which of the following statement conerning X is correct?
A.X has at least four possible structures.
B.X must be a saturated compound.
C.X turns acidified potassium dichromate solution from orange to green.
D.X can be used to make a thermosetting plastic by addition polymeriation.

呢題我完全唔知佢講咩 = = " 好似4個都岩既...

unlock-YM

Fractional distillation係用boiling point的分別去seperate substances，你睇下個圖，佢會將petroleum分成lubricating , diesel, heavy等等幾種oil，但係呢幾種oil唔係單一substance，都係某種mixture。


C3H4F2 can be H3C-HC=CF2, H2FC-HC=HFC, HF2C-HC=H2C and H2C-FC=H2C and etc.
=> A.
From above, X is not saturated. => B is wrong.
The polymer formed is too simple, it should be a thermoplastic. => D is wrong.

小霞的fans

Fractional distillation係用boiling point的分別去seperate substances，你睇下個圖，佢會將petroleum分成lubricating , diesel, heavy等等幾種oil，但係呢幾種oil唔係單一substance，都係某種mixture。


C3H4F ...
unlock-YM 發表於 31/3/2010 04:53 PM

                               
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謝謝你詳盡的解釋^^ " 但係C點解唔岩就唔係太知..

the empirical formula of an organic compound T is CH2O.effervescence occurs when T is added to sodium carbonate solution. T may be
1.HCOOCH3
2.CH3CH(OH)COOH
3.CH3CH2COOH

A.1 only
B.2 only
C.1 and 3 only
D.2 and 3 only
1係ethanoic acid (CH3COOH)吧!?
2同3都係C2H5COOH propanoic acid 吧 !?2個冇分別!?
我唔明CH2O比左咩提示我地去搵答案 -.- " "

unlock-YM

謝謝你詳盡的解釋^^ " 但係C點解唔岩就唔係太知..

the empirical formula of an organic compound T is CH2O.effervescence occurs when T is added to sodium carbonate solution. T may be
1.HCOOCH3
2.C ...
小霞的fans 發表於 1/4/2010 01:10 PM

                               
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1係methyl methanoate，係ester。 => T唔係1。
2係2-hydroxypropanoic acid，係acidic，empirical formula又係CH2O。 => T可以係2。
3係propanoic acid，但係empirical formula唔係CH2O。 => T唔係3。

=> B.

小霞的fans

1係methyl methanoate，係ester。 => T唔係1。
2係2-hydroxypropanoic acid，係acidic，empirical formula又係CH2O。 => T可以係2。
3係propanoic acid，但係empirical formula唔係CH2O。 => T唔係3。

=> B.
unlock-YM 發表於 31/3/2010 05:16 PM

                               
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我想問一問紅字呀..點睇個empirical formula係唔係CH2O架-0-?我唔識睇=.=""所以揀左2同3 (D) =.="

unlock-YM

我想問一問紅字呀..點睇個empirical formula係唔係CH2O架-0-?我唔識睇=.=""所以揀左2同3 (D) =.="
小霞的fans 發表於 1/4/2010 01:29 PM

                               
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先將個formula變做molecular formula。
eg. CH3CH(OH)COOH --> C3H6O3
再將佢化做simplest ratio。
ie. C3H6O3 --> CH2O

小霞的fans

謝謝解答^^

thermosetting plasticcan not be mouldedupon heating.

請問呢句野岩唔岩呢..紅字好似錯..但係加左紫字會唔會係岩呢-.-?

同埋1dm^3=1000cm^3
咁1dm^3=幾多m^3 呀??
thx..

unlock-YM

謝謝解答^^

thermosetting plastic can not be moulded upon heating.

請問呢句野岩唔岩呢..紅字好似錯..但係加左紫字會唔會係岩呢-.-?

同埋1dm^3=1000cm^3
咁1dm^3=幾多m^3 呀??
thx..
小霞的fans 發表於 2/4/2010 03:07 PM

                               
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Thermosetting plastics加熱只會變質或者直接燃燒，所以係唔可以re-mould。

1 m^3 = 100^3 cm^3 = 1000 dm^3

小霞的fans

Thermosetting plastics加熱只會變質或者直接燃燒，所以係唔可以re-mould。

1 m^3 = 100^3 cm^3 = 1000 dm^3
unlock-YM 發表於 1/4/2010 08:24 PM

                               
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唔可以re-mould但係第1次燃燒都可以mould !?

unlock-YM

唔可以re-mould但係第1次燃燒都可以mould !?
小霞的fans 發表於 2/4/2010 05:32 PM

                               
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第一次唔係燃燒，應該係做reaction整隻plastic時mould。