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Edexcel A2 Chemistry Exams -6CH04 (14th June) and 6CH05 (22nd June) Discussion Thread Watch

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    (Original post by WashingPowder)
    This is the pH Curve roughly i believe
    Why is the second straight bit longer ??????. Also it said pka for the second neutrlisation was 7.2 so at 37'5 cm the ph shoukd be 7.2
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    (Original post by Cpj16)
    Methyl secondary alcohols will give a positive result as well
    It was w and z
    are you sure it was a secondary alcohol
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    Exam was really nice. Did struggle a bit with finding out 3 reasons for hydrolysis etc... (always missing one reason)

    There was also a bit of a trick question too with the observation after the thiosulfate ions all reacted. Quite a few people put it turns colourless, but it turns blue-black. Could've sworn that the question turned up a few years ago.
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    (Original post by crimson1234)
    What were the three differences you guys put for acid/alkali hydrolysis. And what 2 bonds did you say we're different for the last bit on the nmr question


    Posted from TSR Mobile
    I honestly just guessed from what I think I heard my friends say a few days ago. But I wrote:

    Acid hydrolysis is reversible, whereas alkaline is not
    Acid hydrolysis makes ester + water, whereas alkaline makes ester + HCl
    Acid hydrolysis makes carboxylic acid, whereas alkaline makes carboxylate salt
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    Why does Edexcel have to be so mean?
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    (Original post by lfcrules)
    Why is the second straight bit longer ??????. Also it said pka for the second neutrlisation was 7.2 so at 37'5 cm the ph shoukd be 7.2
    Yeh The graph isnt completely correct , it should look roughly the same shape though. Should begin at 1.5 and should end at 12-13. Not too sure about the length of the two verticals though
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    (Original post by Funky_Giraffe)
    are you sure it was a secondary alcohol
    yes
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    What did you guys put for why you only use a relatively small amount of phenol?
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    Am I the only one who actually didn't like the paper?
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    (Original post by Pocapoca)
    Am I the only one who actually didn't like the paper?
    I hated it. Everything that I didn't like came up. And as soon as I think that I know acid/base equilibria, Edexcel gives us whatever tf that titration curve question was.
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    (Original post by Pocapoca)
    Am I the only one who actually didn't like the paper?
    I didn't like it either... Paper was so different to all the other past papers. In my opinion I think this paper was really hard. I'm not sure how well I did...
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    C0balt how do you know when you have an excess ?
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    (Original post by Pocapoca)
    Am I the only one who actually didn't like the paper?
    I didn't like it either :/
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    What did you guys get for the PH for the first question? I got 11.0 I'm not sure if that's correct
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    (Original post by Sebastian2597)
    What did you guys get for the PH for the first question? I got 11.0 I'm not sure if that's correct
    I think I got 4.03 or something like that !!
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    (Original post by Funky_Giraffe)
    What did you guys put for why you only use a relatively small amount of phenol?
    I put that if you had too much phenol you wouldn't be able to measure initial rate or something like that.
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    (Original post by jess.olo)
    I think I got 4.03 or something like that !!
    Yeah it was 4.02. I got that wrong lol.
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    (Original post by Don Pedro K.)
    I put that if you had too much phenol you wouldn't be able to measure initial rate or something like that.
    I said it may affect the rate and that you JUST want to add enough to remove bromine
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    (Original post by Don Pedro K.)
    I talked about it in terms of COCl and COOH groups. Is that alright do you think because in the question it said wavenumbers for relevant bonds or groups involved?

    What wavenumbers did you use btw?
    As long as you quoted values and binds you're okay I think
    And I used the C-Cl and O-h but realised now that it was phenol so I lost a mark
    (Original post by lfcrules)
    What did you guys get for the total entropy change and what was the answer for how would you twllnif the acid was in excess. Also for the difference between the two hydrolysis types I mentioned equilibrium and salt formation , any ideas for the third difference ?
    I can't remember but it was quite small like +47 or something
    I said no new precipitate would form on addition of excess acid
    I said eq'm form for acid, carboxylic acid forms for acid but carboxylate for alkaline, alkaline higher yield and acid is slower
    (Original post by jess.olo)
    I said there would be OH for the phenol group in both but for the carboxylic acid group AS well there would be a different OH bond absorption as well?
    I didn't realise there was phenol so I lost a mark there
    (Original post by Funky_Giraffe)
    What did you guys put for why you only use a relatively small amount of phenol?
    If you add a lot of phenol time taken would be too long and so during that time the conc of reactants would've changed significantly therefore the rate at the time of colour change would be significantly different from initial rate
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    (Original post by Sebastian2597)
    What did you guys get for the PH for the first question? I got 11.0 I'm not sure if that's correct
    For the pH of the acid using Ka1?
 
 
 
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