Chemistry unit 6 June 2016

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    (Original post by TheMadHatteress)
    Morle ekshathe morbo shobai :3
    TRUE
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    (Original post by xbuttermelon)
    Nooo I didn't forget about the OH in carboxylic part...lemme show you what I mean and correct me if I'm wrong please.
    Attachment 533141
    Um, it is incorrect, all hydrogen environments are different, so 5 peaks present
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    (Original post by 12103763d)
    Um, it is incorrect, all hydrogen environments are different, so 5 peaks present
    I see. Thanks
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    (Original post by 12103763d)
    Um, it is incorrect, all hydrogen environments are different, so 5 peaks present
    umm no they aren't
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    (Original post by anonymousawesome)
    umm no they aren't
    (Original post by 12103763d)
    Um, it is incorrect, all hydrogen environments are different, so 5 peaks present
    I don't really understand why they are 5, but just asked my chem teacher & said that there are 5 different environments, so the other people must be correct...more like, the answer I crossed out was correct *sob*
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    What did u guys write about the isomer? Where melting temperature was given and samples before and after recrystallization
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    (Original post by Quirky01)
    What did u guys write about the isomer? Where melting temperature was given and samples before and after recrystallization
    I wrote it was the 3 something isomer?
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    (Original post by xbuttermelon)
    Nooo I didn't forget about the OH in carboxylic part...lemme show you what I mean and correct me if I'm wrong please.
    Attachment 533141
    no it is not one hydrogen environment, they are different distances away from the oxygens
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    (Original post by xbuttermelon)
    I don't really understand why they are 5, but just asked my chem teacher & said that there are 5 different environments, so the other people must be correct...more like, the answer I crossed out was correct *sob*
    U need to extend along the chain until the end to derive whether it has same proton environment, which means u should not just see the adjacent carbons attaching same number of hydrogens then derive they have same proton environment
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    (Original post by Quirky01)
    What did u guys write about the isomer? Where melting temperature was given and samples before and after recrystallization
    I wrote it should be the 148 degrees one because impurities can only cause the melt. temp to be lower - so it cant be 142 (range is 144-146) Therefore if recrystallization is carried out again and the sample is furhter purified the mlting temperature would increase and go closer to 148.

    I was honestly clueless whether recrystallisation is done twice though. xD
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    (Original post by 12103763d)
    U need to extend along the chain until the end to derive whether it has same proton environment, which means u should not just see the adjacent carbons attaching same number of hydrogens then derive they have same proton environment
    Ohh! Thank you! Now I understand....need to go over this topic just incase they bring this nmr stuff in unit 5
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    (Original post by RizK)
    I wrote it should be the 148 degrees one because impurities can only cause the melt. temp to be lower - so it cant be 142 (range is 144-146) Therefore if recrystallization is carried out again and the sample is furhter purified the mlting temperature would increase and go closer to 148.

    I was honestly clueless whether recrystallisation is done twice though. xD

    I thought that the temperature range after recrystallization was 144-146.
    So I wrote that it should be the 3 something isomer since it is within that range of temperatures :O
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    (Original post by anonymousawesome)
    What did you guys write for the ammonium disulphate question?
    What is this question?
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    (Original post by Quirky01)
    Could no. Of paeks in low res nmr be used todistinguish P, Q and R? What are your answers guys?
    I wrote P and Q couldn't be distinguished bcz both have 4 proton environments but R could be as it had 2!
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    (Original post by notsoclueless)
    I thought that the temperature range after recrystallization was 144-146.
    So I wrote that it should be the 3 something isomer since it is within that range of temperatures :O
    There was none in the range.. temperatures were
    138, 142, 148
    range falls between the second and third
    equally
    I was talking about a second recrystallization i e further purification
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    (Original post by Quirky01)
    What did u guys write about the isomer? Where melting temperature was given and samples before and after recrystallization
    It was P with 148c
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    In January 16, the A* was 31/50 and full marks were 34/50 so there still hope!! This is the hardest paper I've ever solved and studying past papers didn't even prepare you for the exam. I literally wanted to cry after it😭😭😭😭
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    (Original post by Aimen.)
    It was P with 148c
    But why? After recrystallisation range was 144-146
    I wrote that it would contain p and q in sample B cos avg of their melting temp gave 145 degrees which is in the middle of the range after recrystallisation..
    I might be wrong..very unsure..
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    (Original post by AvWOW)
    haha yeah ooops I meant that.
    Oh and with excess ammonia it was Zn(NH3)4 ^2- or Zn(NH3)6^2- ???
    It's Zn(Nh3)4^2-
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    (Original post by Sandy_Vega30)
    It's Zn(Nh3)4^2-
    The charge should be 2+
    And I think it does not matter whether it's 4 or 6
 
 
 
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