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cyw1226 2013-8-31 04:57 PM

C4H10 boiling point

[size=7][font=Arial]Butaneand 2-methylpropane are chain isomers. Explain why butane[/font]
[font=Arial]hasa higher boiling point than 2-methylpropane.[/font]


[font=Arial]my answer:[/font]
[font=Arial]The main carbon chain of butane is longer than that of 2-methylpropane.[/font]As a result, the dispersion forces among butane molecules are[font=Arial][/font]
[font=Arial]stronger and moreenergy is needed to overcome the forces in boiling.[/font]


[font=Arial]咁答有幾多分??[/font][/size]

Zzlaz 2013-8-31 10:25 PM

我用開contact surface area



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dustbus 2013-8-31 11:05 PM

[quote]原帖由 [i]Zzlaz[/i] 於 2013-8-31 10:25 PM 發表 [url=http://www.discuss.com.hk/redirect.php?goto=findpost&pid=370652444&ptid=22380132][img]http://www.discuss.com.hk/images/common/back.gif[/img][/url]
我用開contact surface area



[img]http://i.discuss.com.hk/d/images/r10/androidD.jpg[/img] [/quote]

關isomer事:smile_35:?

唔係話contact surface area 多D,跟住個van der waals' force會強D咩:o

Zzlaz 2013-8-31 11:47 PM

回覆3 #的帖子

Then?



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Ron~ 2013-9-1 12:10 AM

[quote]原帖由 [i]dustbus[/i] 於 2013-8-31 11:05 PM 發表 [url=http://www.discuss.com.hk/redirect.php?goto=findpost&pid=370655229&ptid=22380132][img]http://www.discuss.com.hk/images/common/back.gif[/img][/url]關isomer事:smile_35:?唔係話contact surface area 多D,跟住個van der waals' force會強D咩:o [/quote]You are right! By considering the contact surface area, the more the contact surface area, the more the van der Waals’s force between molecules, and butane has indeed more contact surface area than 2-methylpropane as it seems to be more bulky.You should consider the length of the chain and then determine which one has more contact surface area in this case. But, of course, they should be isomers, if not, you should think of other factors. And sometimes you will be asked to compare other isomers such as functional group isomers or stereoisomers…[url=http://www.discuss.com.hk/android][img=100,23]http://i.discuss.com.hk/d/images/r10/androidD.jpg[/img][/url]

[[i] 本帖最後由 Ron~ 於 2013-9-1 12:12 AM 使用[url=http://www.discuss.com.hk/android][img=100,23]http://i.discuss.com.hk/d/images/r10/androidD.jpg [/img][/url] 編輯 [/i]]

Ron~ 2013-9-1 12:21 AM

[quote]原帖由 [i]cyw1226[/i] 於 2013-8-31 04:57 PM 發表 [url=http://www.discuss.com.hk/redirect.php?goto=findpost&pid=370633593&ptid=22380132][img]http://www.discuss.com.hk/images/common/back.gif[/img][/url]Butaneand 2-methylpropane are chain isomers. Explain why butanehasa higher boiling point than 2-methylpropane.my answer:The main carbon chain of butane is longer than that of 2-methylpropane ... [/quote]There are some key words that you didn’t mention in you answer and they are what markers focus on.
Dispersion force should be replaced by Van der Waals’s force or intermolecular force. And the reason(eg: contact surface area) causing the result should also be mentioned.



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