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    Hi guys!
    Since there was no thread for the resit I thought of making one
    I hope this thread will be able to help you a bit with revision and clear some doubts.
    Spec
    http://www.edexcel.com/migrationdocu...4%20250510.pdf
    Past papers

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


    Feel free to ask any question on this unit and we will try our best to help. Good luck!
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    (Original post by AS01)
    Hi guys!
    Since there was no thread for the resit I thought of making one
    I hope this thread will be able to help you a bit with revision and clear some doubts.
    Spec
    http://www.edexcel.com/migrationdocu...4%20250510.pdf
    Past papers

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


    Feel free to ask any question on this unit and we will try our best to help. Good luck!
    woop Hopefully it won't be too difficult to go over again !

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

    ... are you doing Unit 2 as well ?
    hope so
    No I am not.
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    What are the phases used for the different types of chromatography?
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    (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
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    (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
    Thanks

    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?
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    (Original post by SKK94)
    Thanks

    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 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 Hope that makes sense... and yes the stationary phase is usually solid I believe.
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    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 )...?
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    (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 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 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?
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    (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.
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    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 ?
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    http://www.mediafire.com/?jycceak1lf44c
    they are here.
    Attached Images
  1. File Type: pdf 6CH04_01_rms_20130307.pdf (276.0 KB, 1881 views)
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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
    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
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    (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
    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 -.-

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    (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
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    (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
    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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    hey guys! how is revision going?
    Does anyone have examiner report for Jan 2013 paper?
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    (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*
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    (Original post by SKK94)
    Here's the link
    http://www.mediafire.com/folder/fpbjppc090a8c/Chemistry

    *Thanks to Abod*
    thanks a lot!!! I wannted to guess what might come up
 
 
 
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