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Ed excel Chemistry A2 12th June, Wednesday

Hi guys!
Since there was no thread for the resit I thought of making one :biggrin:
I hope this thread will be able to help you a bit with revision and clear some doubts.
Spec
http://www.edexcel.com/migrationdocuments/GCE%20New%20GCE/UA024832%20GCE%20in%20Chemistry%20Issue%204%20250510.pdf
Past papers

Spoiler


NMR questions (since there was a big 7 mark question on previous paper :tongue: )

Spoiler



Feel free to ask any question on this unit and we will try our best to help. Good luck!

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Reply 1
Original post by AS01
Hi guys!
Since there was no thread for the resit I thought of making one :biggrin:
I hope this thread will be able to help you a bit with revision and clear some doubts.
Spec
http://www.edexcel.com/migrationdocuments/GCE%20New%20GCE/UA024832%20GCE%20in%20Chemistry%20Issue%204%20250510.pdf
Past papers

Spoiler


NMR questions (since there was a big 7 mark question on previous paper :tongue: )

Spoiler



Feel free to ask any question on this unit and we will try our best to help. Good luck!


woop :biggrin: Hopefully it won't be too difficult to go over again !

... are you doing Unit 2 as well ? :smile:
Reply 2
Original post by posthumus
woop :biggrin: Hopefully it won't be too difficult to go over again !

... are you doing Unit 2 as well ? :smile:


hope so
No I am not.
Reply 3
What are the phases used for the different types of chromatography?
Reply 4
Original post by SKK94
What are the phases used for the different types of chromatography?


Stationary Phase & Mobile phase...

Mobile phase can be considered as the solvent/phase that transports the sample.

Stationary phase is one that interacts with this mobile phase, depending on what is present in the sample... the mobile phase will make it's way through the stationary phase in a certain amount of time.

This time is called the retention time and is a unique characteristic for the sample being tested :smile:
Reply 5
Original post by posthumus
Stationary Phase & Mobile phase...

Mobile phase can be considered as the solvent/phase that transports the sample.

Stationary phase is one that interacts with this mobile phase, depending on what is present in the sample... the mobile phase will make it's way through the stationary phase in a certain amount of time.

This time is called the retention time and is a unique characteristic for the sample being tested :smile:


Thanks :smile:

So the sample moves due to intermolecular forces with the mobile phase; and the mobile phase moves due to intermolecular forces with the solid phase?
Can the sample also have intermolecular forces with the solid phase?
Reply 6
Original post by SKK94
Thanks :smile:

So the sample moves due to intermolecular forces with the mobile phase; and the mobile phase moves due to intermolecular forces with the solid phase?
Can the sample also have intermolecular forces with the solid phase?


erm not quite

for example in GLC the sample moves due to pressure provided by the system... the stationary face itself slows it down due to interactions (such inter-molecular forces).
So it does quite the opposite of what you said :smile: it kind of opposes the flow... imagine if the mobile phase could form hydrogen bonds with the stationary phase... then it would get slowed down quite a bit :smile: Hope that makes sense... and yes the stationary phase is usually solid I believe.
Reply 7
Anybody did alternative to practical, on 15th June...? there was a pretty bad NMR question.. we could expect something twisted like that in Unit 4 too right.. what do y'all think ? any resources to practice NMR ( other than pastpapers )...? :smile:
Reply 8
Original post by posthumus
erm not quite

for example in GLC the sample moves due to pressure provided by the system... the stationary face itself slows it down due to interactions (such inter-molecular forces).
So it does quite the opposite of what you said :smile: it kind of opposes the flow... imagine if the mobile phase could form hydrogen bonds with the stationary phase... then it would get slowed down quite a bit :smile: Hope that makes sense... and yes the stationary phase is usually solid I believe.


hey.. can u explain to me what happens to the solubility of aldehydes and ketones in water, when the length of chain increases?
Reply 9
Original post by Amila888
hey.. can u explain to me what happens to the solubility of aldehydes and ketones in water, when the length of chain increases?


Solubility will decrease as rest of chain will only have London forces, which are much weaker than Hydrogen Bonds.
Reply 10
Can anyone please help me..in jan 2013 q19 c i) in the data given its said that X is a neutral organic compound..the marking scheme says it means its not a carboxylic acid..i dont seem to understand this :/ can someone explain this?

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Original post by AT95
Can anyone please help me..in jan 2013 q19 c i) in the data given its said that X is a neutral organic compound..the marking scheme says it means its not a carboxylic acid..i dont seem to understand this :/ can someone explain this?

Posted from TSR Mobile


Do you have the Question paper & MS ?
Original post by AT95
Can anyone please help me..in jan 2013 q19 c i) in the data given its said that X is a neutral organic compound..the marking scheme says it means its not a carboxylic acid..i dont seem to understand this :/ can someone explain this?

Posted from TSR Mobile


Well I would think Carboxylic acid is not neutral because it dissociates quite a bit... the H+ is easily liberated and it's pH will be fairly low.

I think I did ethanol for that one in January, pH must be around 7

God damn it, I hated this paper so much :frown:
Reply 14
Original post by posthumus
Well I would think Carboxylic acid is not neutral because it dissociates quite a bit... the H+ is easily liberated and it's pH will be fairly low.

I think I did ethanol for that one in January, pH must be around 7

God damn it, I hated this paper so much :frown:


Ohh okay. But the third point says that its either a primary or secondary alcohols, so cant they dissociate to give OH-??
I feel dumb for not knowing these things -.-

Posted from TSR Mobile
Original post by AT95
Ohh okay. But the third point says that its either a primary or secondary alcohols, so cant they dissociate to give OH-??
I feel dumb for not knowing these things -.-

Posted from TSR Mobile


I think the bond is strong covalent therefore it does not dissociate, I've also never heard of alcohols being a base, but it's a good question... & first time I've had to think about that :tongue:
Reply 16
Original post by posthumus
I think the bond is strong covalent therefore it does not dissociate, I've also never heard of alcohols being a base, but it's a good question... & first time I've had to think about that :tongue:


So carboxylic acids have the same OH bond, the one that gives away H+ like you and the mark scheme said. So why cant alcohols give away H+?
And yes m sure alcohols arent bases too. Feel stupid for asking that now.. anyway.

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Reply 17
hey guys! how is revision going?
Does anyone have examiner report for Jan 2013 paper?
Reply 18
Original post by AS01
hey guys! how is revision going?
Does anyone have examiner report for Jan 2013 paper?


Here's the link
http://www.mediafire.com/folder/fpbjppc090a8c/Chemistry

*Thanks to Abod*
Reply 19


thanks a lot!!! I wannted to guess what might come up :colone:

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