Chemistry unit 6 June 2016

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    (Original post by Quirky01)
    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..
    I'm sorry but you seem to be wrong cuz they asked us for a compound and not compounds!
    I read in an examiner report that no compound can have higher m.p than original sample. Plus i did sat 2 chem recently and it had a topic called "melting point depression due to impurities", so I knew impurities can only lower m.p and then I thought that even after recrystallisation it may still be somewhat impure so the original compound's m.p had to be higher than sample.. and I'm kinda sure about what I'm saying cuz my supergenius chem teacher reconfirmed me x)
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    Btw who has physics on Thursday? x)
    And is there some thread for that?
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    Hey guys, the exam was SO freaking hard, I think I messed up so bad. Q.2 made me so nervous and I couldn't prove the show that! ALSO I am not sure about any of my answers

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    I wanna make this exam period call black may/june, I have prepared for coming disastrous exams...
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    (Original post by 12103763d)
    I wanna make this exam period call black may/june, I have prepared for coming disastrous exams...
    Same!! I am really frustrated and demotivated for the upcomining exams!!
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    (Original post by Aimen.)
    I wrote P and Q couldn't be distinguished bcz both have 4 proton environments but R could be as it had 2!
    I wrote that they all can be distinguished due to having different hydrogen environments and therefore different number of peaks, but I guess I was wrong because I didn't count the OH of carboxylic acid in one group :/
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    (Original post by PlayerBB)
    Same!! I am really frustrated and demotivated for the upcomining exams!!
    All exams in a series are never hard so If we've encountered hard biology 6 and chem 6, I believe upcoming exams would be quite easy x)
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    (Original post by PlayerBB)
    I wrote that they all can be distinguished due to having different hydrogen environments and therefore different number of peaks, but I guess I was wrong because I didn't count the OH of carboxylic acid in one group :/
    P and Q had same 4 proton environments and R had 2 as far as I believe.
    Anyway it's over! let the bygones be the bygones... and work hard for the next stage!
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    (Original post by Aimen.)
    P and Q had same 4 proton environments and R had 2 as far as I believe.
    Anyway it's over! let the bygones be the bygones... and work hard for the next stage!
    (Original post by Aimen.)
    All exams in a series are never hard so If we've encountered hard biology 6 and chem 6, I believe upcoming exams would be quite easy x)
    Honestly, I don't know how I managed to get out of the exam hall, I was in a complete shock after and during the exam, not focus at all, it seems I made many stupid mistakes which I am subbing and Biology unit 6 definitely went much better than chemistry unit 6 but like hoping for the best and praying for that low grade boundaries!!

    All the best for people doing physics on Thursday!!
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    (Original post by Aimen.)
    I'm sorry but you seem to be wrong cuz they asked us for a compound and not compounds!
    I read in an examiner report that no compound can have higher m.p than original sample. Plus i did sat 2 chem recently and it had a topic called "melting point depression due to impurities", so I knew impurities can only lower m.p and then I thought that even after recrystallisation it may still be somewhat impure so the original compound's m.p had to be higher than sample.. and I'm kinda sure about what I'm saying cuz my supergenius chem teacher reconfirmed me x)
    Did you also give the lowest one?
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    (Original post by Ayman!)
    I wrote the first two points of both of your answers, unsure about my last one.



    This was my last point, haha - not sure how valid it is, but I feel like it's wrong.
    Yeah, These were my three answers as well, the salt bridge, the vanadium electrode and the exclusion of H+
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    (Original post by Ayman!)
    Did you also give the lowest one?
    Not 142c , I chose middle one 148c
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    (Original post by Aimen.)
    Not 142c , I chose middle one 148c
    I also chose the middle one because the range was 144 to 146.
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    (Original post by RizK)
    Don't discuss the paper within 12 hours. You will only raise the grade boundaries.

    That being said, I kept getting 0.056 for that show that question, wtf
    You get the volume of NaOH used to neutralise HCl which was 4cm cube. Then you substract that with 42.4cm cubed which will give you volume of 38,4 to neutralise ethanoic acid. From that volume now you can get the moles of ethanoic acid in 5cm cubed and then in 25cm cubed.
    I wasted so much of time in that question and because of that I couldn't finish the paper and left like 8 marks
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    What would be the answer to the question that asked how Kc value will be affected if less volume was taken?? (I dont exactly remember the question)
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    (Original post by Varun Gupta)
    You get the volume of NaOH used to neutralise HCl which was 4cm cube. Then you substract that with 42.4cm cubed which will give you volume of 38,4 to neutralise ethanoic acid. From that volume now you can get the moles of ethanoic acid in 5cm cubed and then in 25cm cubed.
    I wasted so much of time in that question and because of that I couldn't finish the paper and left like 8 marks
    i got 0.0212 moles of naoh and reduced 0.01 moles for hcl...
    i got 0.0112 moles in 1:1 ratio for the ethanoic acid in 5cm^3
    then multiplied by 5
    and got the wrong answer
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    No thread for physics unit 6?
    What was the full ums mark for physiscs unit 6 in january 2016?
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    (Original post by Aimen.)
    Btw who has physics on Thursday? x)
    And is there some thread for that?
    What was the full ums for u6 in jan16? I mean physics..
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    (Original post by Aimen.)
    Btw who has physics on Thursday? x)
    And is there some thread for that?
    http://www.thestudentroom.co.uk/show....php?t=4080671
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    Did anybody get the Kc Value to be 0.351?
 
 
 
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