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OCR Chemistry A Exam Thread (Breadth - May 27 2016 and Depth - June 10 2016) Watch

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    (Original post by kiwifruit99)
    Purifying an organic liquid:
    We normally do this after a distillation.
    1. Put the distillate of organic liquid into a separating funnel.
    2. Add sodium chloride to separate the aqueous layer from the organic layer.
    3. add sodium hydrogen carbonate to react an remaining acid.
    4. Run organic layer into a conical flask
    5. Add a drying agent (such as magnesium sulphate) to remove waters of crystallization.
    6. Distilled the remaining liquid to obtain pure product.




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    Once again thanks! I've never come across this. Is it the cyclohexane thing?

    GOOD LUCK EVERYONE
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    Good luck!!!
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    (Original post by Cherx)
    Once again thanks! I've never come across this. Is it the cyclohexane thing?

    GOOD LUCK EVERYONE
    Nope it was just there along with organic synthesis in the textbook. Good luck!


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    Is there a way to avoid getting the signs wrong in enthalpy calculations
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    It's almost time, good luck everyone, make sure you read each question carefully (twice if needed) answer every question and be calm!!
    For any last minute queries don't hesitate to ask.

    Also do we need to know the practicals on equilibrium?
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    (Original post by asdfghjklp)
    Is there a way to avoid getting the signs wrong in enthalpy calculations
    Depends, if you're talking about q=mc/\T then for /\H = -q/n

    If it's on combustion and stuff, then do the calculations twice make sure you copied down correctly
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    (Original post by asinghj)
    It's almost time, good luck everyone, make sure you read each question carefully (twice if needed) answer every question and be calm!!
    For any last minute queries don't hesitate to ask.

    Also do we need to know the practicals on equilibrium?
    There was a lot of equilbrium in the breadth so its very unlikely to come up again
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    (Original post by asdfghjklp)
    There was a lot of equilbrium in the breadth so its very unlikely to come up again
    Hope none comes up cos I know nothing about the reactions
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    When do you multiply by 24?
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    That was yet another fantastic paper from OCR, reckon grade boundaries are going to be high!
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    I'm really mad at myself bc at the last minute I changed my answer for the last question because I got confused about the secondary carbocation😭😭
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    I thought that was a good paper. I ****ed up the percentage yield question because I couldn't get anything other than 100.3%, but I was fairly confident on everything else.
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    (Original post by amysed)
    I'm really mad at myself bc at the last minute I changed my answer for the last question because I got confused about the secondary carbocation😭😭
    what did you get get?
    I think it was butanoic acid

    (Original post by LordStark)
    I thought that was a good paper. I ****ed up the percentage yield question because I couldn't get anything other than 100.3%, but I was fairly confident on everything else.
    think I got around 67%

    I was a bit iffy on the experimental questions
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    I ran out of time so badly I'm really annoyed at myself😩
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    (Original post by alkaline.)
    what did you get get?
    I think it was butanoic acid
    yeah I got butanoic acid originally but I stupidly changed it to 2-methylpropanoic acid I think🔫
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    4.46*10^6 Pa
    1.8 something for mass
    67% yield
    Metal - Ca
    9*10^-4 for gs-1- rates
    Did anyone say clamp stand needed for oxidation??
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    I ****IN LOVED THAT. IT WAS SOOOO EASY.

    grade boundaries are going to be SOOO high lmao 99% for an A


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    Surely it was 2-methylpropanoic acid , otherwise how would you get a secondary carbocation with butanoic acid?
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    (Original post by Danielle_16)
    I ran out of time so badly I'm really annoyed at myself😩
    same happened to me, managed to start the final question and was working towards the correct answer but ran out of time
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    Did I do a different paper to all of you or something? I hated that paper so much ahhh
 
 
 
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