chemistry既問題‥

小霞的fans · 發表於 2/4/2010 05:53 PM

第一次唔係燃燒，應該係做reaction整隻plastic時mould。
unlock-YM 發表於 1/4/2010 09:34 PM

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我好混亂

書第1頁寫thermosetting plasticsdo not melt or soften on heating.
但係後面寫a thermosetting plastic also consists of seperate long chains during its first stage of formation.Henceit goes soft upon heatingand can be moulded into the desired shape.

紅字點解會咁架

佢幾時mould到架><""

unlock-YM · 發表於 2/4/2010 06:42 PM

我好混亂
書第1頁寫thermosetting plastics do not melt or soften on heating.
但係後面寫a thermosetting plastic also consists of seperate long chains during its first stage of formation.Hence it g ...
小霞的fans 發表於 2/4/2010 05:53 PM

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我估重點係"during its first stage of formation"，即係同我之前講一樣，form polymer時係可以mould，但係reaction後期會令佢structure變成完全的thermosetting plastic。

小霞的fans · 發表於 2/4/2010 10:28 PM

我估重點係"during its first stage of formation"，即係同我之前講一樣，form polymer時係可以mould，但係reaction後期會令佢structure變成完全的thermosetting plastic。
unlock-YM 發表於 1/4/2010 10:42 PM

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喔..原來係咁..
concerning silicon dioxide,
3)each silicon atom is joined to two oxygen atoms.
呢句點解錯既..佢個formula明明係SiO2咪即係each silicon atom is joined to two oxygen atoms.點解錯架??

unlock-YM · 發表於 2/4/2010 10:30 PM

喔..原來係咁..
concerning silicon dioxide,
3)each silicon atom is joined to two oxygen atoms.
呢句點解錯既..佢個formula明明係SiO2咪即係each silicon atom is joined to two oxygen atoms.點解錯架??
小霞的fans 發表於 2/4/2010 10:28 PM

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SiO2係giant covalent structure。

小霞的fans · 發表於 2/4/2010 10:38 PM

睇返f.4本書..佢寫
each silicon atom is joined to four oxygen atoms by covalent bonds while each oxygen atom is joined to two silicon atoms by covalent bonds.我唔明點解..佢佢個formula明明係SiO2..好似書咁寫咪變左Si2O 囉 =.=""

unlock-YM · 發表於 2/4/2010 10:41 PM

睇返f.4本書..佢寫
each silicon atom is joined to four oxygen atoms by covalent bonds while each oxygen atom is joined to two silicon atoms by covalent bonds.我唔明點解..佢佢個formula明明係SiO2..好似書 ...
小霞的fans 發表於 2/4/2010 10:38 PM

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有圖會易理解少少，比例上係SiO2，但係其實整體係由Si同O組成的giant network，唔係discrete molecules。

小霞的fans · 發表於 2/4/2010 10:50 PM

喔喔..麻煩哂你真係唔好意思>< "" 幫左我咁多..謝謝^^
仲有1題我計到岩既答案但係搵唔到快既方法計-.-""
32.2g of an oxide of metal M , when completely reduced by carbon,produced 4.95g of carbon dioxide.what is the empirical formula of the oxide?
(relative atomic masses:C=12.0 , O=16.0 , M=63.5)
A.MO
B.M2O
C.MO2
D.M2O3
計到carbon dioxide既mole數=4.95/12+16x2 = 0.1125mol 跟住應該點做呢@@...

unlock-YM · 發表於 2/4/2010 11:02 PM

本帖最後由 unlock-YM 於 2/4/2010 11:03 PM 編輯

Mass of O in MOx = 4.95 x 32 / 44 = 3.6
Mass of M = 32.2 - 3.6 = 28.6
M : O = 28.6/63.5 : 3.6/16 = 2 : 1
=> B.

hk56740 · 發表於 2/4/2010 11:18 PM

有圖會易理解少少，比例上係SiO2，但係其實整體係由Si同O組成的giant network，唔係discrete molecules。
unlock-YM 發表於 2/4/2010 10:41 PM

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正確黎講係empirical formula

unlock-YM · 發表於 2/4/2010 11:20 PM

正確黎講係empirical formula
hk56740 發表於 2/4/2010 11:18 PM

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Oh, thanks.

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[求助] chemistry既問題‥