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OCR A Chemistry Paper 2 Unofficial Mark scheme Watch

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    (Original post by iamDev)
    Did we need to state structure of M and N
    Nope
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    (Original post by iamDev)
    It was weakly acidic as ph 5. So it's carboxylic acid or phenol.not c acid because it didn't react with carbonate. Must be phenol
    I just put an alcohol, I didn't even think to specify phenol 😧
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    Ok I'm pretty damn confused. Recrystallisation is the method of purifying the product from the impure solid, so the purity of the product would be 100%? Surely you have to do purity from grams of the pure product of of grams of the impure solid?????
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    You recrystallise the solid using minimum amount of hot solvent, filter it to remove insoluble impurities, then let the filtered solution cool so the crystals reform then filter it again using a buchner flask and reduced pressure, and you're left with the crystals then wash them with cold solvent. Then to test purity you test the melting point using an electric furnace (not sure of the actual name for it). You put a small sample in a capillary tube with one end sealed and watch from the viewing port the solid melting and record the range of temperatures it melted over, compare it to known ranges/values. Pure substances have a sharp range, impure have a lower melting point and wider range.
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    Is anyone able to start off a google doc we can all contribute to so we can estimate our marks?
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    how were you meant to answer the beta-carotene question without knowing how many carbon atoms were in the two rings?

    im convinced it's impossible
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    (Original post by Asiangirl101)
    Produces 1 water
    But 0.1 mole
    So it's 6.02 x 10^22
    But it was a dicarboxylic acid so 2 waters would have been produced so wouldn't the moles be 0.2 making 3.01x10^22 the answer?


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    What is an ester?
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    (Original post by Haza296)
    how were you meant to answer the beta-carotene question without knowing how many carbon atoms were in the two rings?

    im convinced it's impossible
    They gave you the moles of it and then you can calculate the moles of hydrogen as it gave you the volume, you can then calculate the molar ratio.
    As it was an alkane as the product, use 2n+2 as they gave you the number of carbon atoms and then you can work out the number of hydrogens in the reactant


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    (Original post by Jay52)
    What is an ester?
    I
    C=O
    I
    O
    I
    R
    (flip your phone sideways if this works)


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    (Original post by student2034)
    They gave you the moles of it and then you can calculate the moles of hydrogen as it gave you the volume, you can then calculate the molar ratio.
    As it was an alkane as the product, use 2n+2 as they gave you the number of carbon atoms and then you can work out the number of hydrogens in the reactant


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    it was a cycloalkane though. 2n + 2 wouldn't work, thats for straight and branched chained alkanes
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    (Original post by student2034)
    They gave you the moles of it and then you can calculate the moles of hydrogen as it gave you the volume, you can then calculate the molar ratio.
    As it was an alkane as the product, use 2n+2 as they gave you the number of carbon atoms and then you can work out the number of hydrogens in the reactant


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    Alicyclic hydrocarbons like cyclohexane do not follow the 2n+2 formula
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    (Original post by Haza296)
    it was a cycloalkane though. 2n + 2 wouldn't work, thats for straight and branched chained alkanes
    f***


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    What did you get for the multiple choice about which would produce the most acidic solution when reacted with water. Did people put the ester, carboxylic Acid or acyl chloride?
    (I can't remember the 4th option)?
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    (Original post by Shahani)
    for the purification question (6 marker), I forgot to write about checking for the melting point to check the purity of the compound, but i wrote everything else and got a percentage yield of 71. Would i at least get 4 marks?
    with the new levelled questions you might not because it specifically asks you to do it in the question. it depends on what is required for each level
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    (Original post by JayP454)
    did you have to name the oxidised products of butanal and butanoic acid? bcuz i just drew them i forgot what the question asked
    Nah pretty sure you didn't they just said draw the structure
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    (Original post by dhr_jacobson)
    So For the last question everyone has been saying it's the bottom one, but I can only see evidence for it being the top structure (I drew at H spec aswell)Attachment 665856
    I got the top one as well.. pretty sure it was the three methyl groups closer to the C double O bond
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    (Original post by Thedkk)
    What did you get for the multiple choice about which would produce the most acidic solution when reacted with water. Did people put the ester, carboxylic Acid or acyl chloride?
    (I can't remember the 4th option)?
    Acyl chloride. Most reactive right??
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    (Original post by Shahani)
    I wrote about recrystallisation and filtration just forgot to say to check the melting point. would that still give me 2 ?
    i did a question in one of the specimen papers and forgot to include a bit of it but because they specifically asked for that bit as well in the question I got no marks even though I wrote about everything else because of the levelled markscheme. Not sure if it'll be the same for this one though, it depends what's required for each level
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    (Original post by M.E.L)
    I got the top one as well.. pretty sure it was the three methyl groups closer to the C double O bond
    The problem I have is that my understanding of H NMR tells me that the bottom structure, which everyone seems to have gotten, contradicts the spectra
 
 
 
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