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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 DezzleMon)
    Theyve asked a question about diprotic acid titrations before though and that was totally allowed so I shouldnt think they will null it. Theyre allowed to apply the knowledge without sticking 100% to the spec.
    But they've never asked us to draw a titration curve for it which is totally off spec because the specification clearly states MONOPROTIC curves. When they asked about di protic carboxylic acids, they used slight application of knowledge but nothing which directly contradicts their specification.
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    C0balt Whizbox Guys would I get marks for the question about differences between D and ethanol and salicylic acid and ethanol for saying that with D you get steamy white fumes, and with D it goes to completion?
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    (Original post by Don Pedro K.)
    C0balt Whizbox Guys would I get marks for the question about differences between D and ethanol and salicylic acid and ethanol for saying that with D you get steamy white fumes, and with D it goes to completion?
    I think you will
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    (Original post by C0balt)
    I think you will
    Here's to hoping lol...
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    (Original post by Don Pedro K.)
    C0balt Whizbox Guys would I get marks for the question about differences between D and ethanol and salicylic acid and ethanol for saying that with D you get steamy white fumes, and with D it goes to completion?
    Did you mention steamy white fumes of HCl?

    For that question i mentioned equilibrium rather than completion and H2O rather than HCl
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    (Original post by C0balt)
    I think you will
    what about fumes of hcl gas evolved?
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    (Original post by Whizbox)
    Did you mention steamy white fumes of HCl?

    For that question i mentioned equilibrium rather than completion and H2O rather than HCl
    No I just said steamy white fumes :/ I mean I knew it was HCl but...xD Do you get steamy white fumes in the other one?
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    (Original post by pumelman82)
    I think I got the titration curve question right. What if the mark scheme for this paper says DO NOT MARK for that question because people are calling in saying it was against the spec? I may have lost 6 marks because people are protesting about a question they couldn't do, but edexcel gave you enough information to do it??? What do you think they'll do?
    I hope they mark it because that twill lower the gb lol. Anyway I think it was a fair question because they didn't just throw an empty graph paper at us and told us to draw a curve for diprotic, but they gave us loads of clues - such as telling as that two moles of OH- is required to neutralise one mole of H2S, the values of two Ka (and if you knew about half neutralisation point you'd know what points to plot), initial pH, telling us to indicate equivalence pointS (implying that there was more than one)...
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    (Original post by Don Pedro K.)
    No I just said steamy white fumes :/ I mean I knew it was HCl but...xD Do you get steamy white fumes in the other one?
    I don't think you would get steamy fumes in the other one, but it depends on what the mark scheme says, you may get it
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    (Original post by ilovecake123)
    what about fumes of hcl gas evolved?
    I think you'll get a mark for that. I hope so anyway i just said HCl gas forms for D but not for the acid lol
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    For how you know the acid is in excess I wrote that the salt (or whatever it was) stops precipitating out of the solution. I also wrote that you can add Sodium Carbonate and you'll observe effervescence and fizzing. Would this get the mark?
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    (Original post by C0balt)
    I hope they mark it because that twill lower the gb lol. Anyway I think it was a fair question because they didn't just throw an empty graph paper at us and told us to draw a curve for diprotic, but they gave us loads of clues - such as telling as that two moles of OH- is required to neutralise one mole of H2S, the values of two Ka (and if you knew about half neutralisation point you'd know what points to plot), initial pH, telling us to indicate equivalence pointS (implying that there was more than one)...
    The two vertical regions were at 25cm3 and 50cm3 right?
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    (Original post by C0balt)
    I think you'll get a mark for that. I hope so anyway i just said HCl gas forms for D but not for the acid lol
    same
    you know to the titration curve what do you think the point break down will be? and did you do a vertical region at 50cm3?
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    (Original post by Whizbox)
    I don't think you would get steamy fumes in the other one, but it depends on what the mark scheme says, you may get it
    Hope so lol
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    (Original post by Whizbox)
    The two vertical regions were at 25cm3 and 50cm3 right?
    yeah
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    (Original post by C0balt)
    I hope they mark it because that twill lower the gb lol. Anyway I think it was a fair question because they didn't just throw an empty graph paper at us and told us to draw a curve for diprotic, but they gave us loads of clues - such as telling as that two moles of OH- is required to neutralise one mole of H2S, the values of two Ka (and if you knew about half neutralisation point you'd know what points to plot), initial pH, telling us to indicate equivalence pointS (implying that there was more than one)...
    Exactly.... I felt that paper could have been a lot worse. Yes they asked unusual stuff but you weren't completely in the dark about how to answer stuff. They gave more than enough clues.
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    (Original post by Science&Despair)
    Im thinking 66 for an A grade
    I pray to god that is the case!!
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    Anyone got an unofficial mark scheme going??
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    (Original post by ilovecake123)
    same
    you know to the titration curve what do you think the point break down will be? and did you do a vertical region at 50cm3?
    how many marks was that curve?
    I think points to look out for are
    - vertical sections at 25 and 50
    - start at pH 1.5
    - end at pH 12-13
    - pH 1.9 (iirc) at 12.5cm3
    - pH 7.2 (iirc) at 37.5cm3
    - general shape
    - marking equivalence points at middle of vertical sections
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    (Original post by C0balt)
    how many marks was that curve?
    I think points to look out for are
    - vertical sections at 25 and 50
    - start at pH 1.5
    - end at pH 12-13
    - pH 1.9 (iirc) at 12.5cm3
    - pH 7.2 (iirc) at 37.5cm3
    - general shape
    - marking equivalence points at middle of vertical sections
    It was 5 marks
 
 
 
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