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    heys


    need sum revision tips and i wnt to kno do any of u kno a site where i can practice all my Ka and pH calculations?
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    Past papers, working through the exercises in the books, and revision guides
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    shud be an easy paper right?

    who else is doin this?????????????
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    Yep I am. Just did the Jan 05, which was quite a good, but at times different and hard, paper.
    Just do all the past papers, and the questions in 'Revise A2 Chemistry for OCR A' if you have it, are quite useful.
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    yeh i think ill jus do all my past papers...does anyone hve any idea wat the last synoptic question cud be on???or is it just anything?
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    (Original post by endeavour)
    Yep I am. Just did the Jan 05, which was quite a good, but at times different and hard, paper.
    Just do all the past papers, and the questions in 'Revise A2 Chemistry for OCR A' if you have it, are quite useful.
    I just did that paper too.. I thought it was quite hard compared to some of the others...

    Btw, for OCR Chemistry unifying, we don't need to "learn our whole AS" do we? Cos it's mainly on the 3 chapters they give us to revise on it, with extra random calculations.. But they won't ask us anything like, erm... atomic radii from foundation wil they???
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    --------------------------------------------------------------------------------

    yeh i think ill jus do all my past papers...does anyone hve any idea wat the last synoptic question cud be on???or is it just anything?
    make sure you can do empirical formula calculations and basic mol. calculations aswell - though i say basic what i mean is they are very long questions you need to know what info and equations to use and when etc etc. All in all you cant gaurentee
    what the synoptic is going to be on i dont think.
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    Bond angles could come up too as well as some organic reactions e.g. oxidation of primary and secondary alcohols so make sure you know oxidising reagents and any obervations
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    (Original post by violet)
    I just did that paper too.. I thought it was quite hard compared to some of the others...

    Btw, for OCR Chemistry unifying, we don't need to "learn our whole AS" do we? Cos it's mainly on the 3 chapters they give us to revise on it, with extra random calculations.. But they won't ask us anything like, erm... atomic radii from foundation wil they???
    its not on any of the papers! i havnt seen jan 05! what kinda stuff is on it? :mad: id like too! just like bits of how har how fast and moles come up dont they! they best not put foundation in anyway!
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    Partial pressure, equilibrium, free radicals, drawing dot and cross diagram of O3 (?!) erm indicators and the drawing a graph for it and then just pH, Kc and the normal stuff.. I think!
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    (Original post by violet)
    Partial pressure, equilibrium, free radicals, drawing dot and cross diagram of O3 (?!) erm indicators and the drawing a graph for it and then just pH, Kc and the normal stuff.. I think!
    gah!! see! its so random stuff they put on it! tommorows will be full of suprises im sure! do you have msn/yahoo or aim violet? pm me it if you do
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    Get OCR papers from here http://www.emailed.org.uk/
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    (Original post by endeavour)
    Get OCR papers from here http://www.emailed.org.uk/
    dude i love you
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    Anyone sitting Chains, Rings and Spectroscopy? Im resiting it from January
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    (Original post by froggymills)
    Anyone sitting Chains, Rings and Spectroscopy? Im resiting it from January
    yeap and me! im gonna bottom out on everything tommorow probably! cause unifying is just too hard! and chains and rings... i doubt ill get more than a D! good luck!
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    Can anyone help?
    i came a cross a question on a past paper- jan2004- question1(!)
    the mark scehem said the gaps were 7.5, and 5 and 5. the question says that the amount of ethanoic acid remaining at the end is 1 mol....

    how the hell did they get that??

    i'm also re-taking chains, rings, spec, i was 3 marks off a B!
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    (Original post by CogitoErgoSum)
    Can anyone help?
    i came a cross a question on a past paper- jan2004- question1(!)
    the mark scehem said the gaps were 7.5, and 5 and 5. the question says that the amount of ethanoic acid remaining at the end is 1 mol....

    how the hell did they get that??

    i'm also re-taking chains, rings, spec, i was 3 marks off a B!
    Jan04 UC q1:
    We're told that "1 mol ethanoic acid remained". So CH3COOH at equilibrium = 1 mol.
    Amount of CH3COOC2H5 at equilibrium = 6 moles (of CH3COOH initially) - 1 mol = 5 moles
    Amount of C2H5OH = 12.5 - 5 = 7.5 moles

    CH3COOC2H52O = 1:1 ratio
    so H2O is also 5 moles.
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    (Original post by endeavour)
    Jan04 UC q1:
    We're told that "1 mol ethanoic acid remained". So CH3COOH at equilibrium = 1 mol.
    Amount of CH3COOC2H5 at equilibrium = 6 moles (of CH3COOH initially) - 1 mol = 5 moles
    Amount of C2H5OH = 12.5 - 5 = 7.5 moles

    CH3COOC2H52O = 1:1 ratio
    so H2O is also 5 moles.
    i'm doomed to just never understand chemistry! why did you take away 5 from 12.5?

    (sorry to be very annoying!)
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    Because you started off with 6mol CH3COOH and at the end there was 1 mol.
    That means that 5 mol reacted.
    And because it's a 1:1 ratio with C2H5OH, that means the same amount must react.
    So if you started off with 12.5mol C2H5OH then you take away 5 that reacted, you get 7.5 mol.

    Hope that helps
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    (Original post by violet)
    Because you started off with 6mol CH3COOH and at the end there was 1 mol.
    That means that 5 mol reacted.
    And because it's a 1:1 ratio with C2H5OH, that means the same amount must react.
    So if you started off with 12.5mol C2H5OH then you take away 5 that reacted, you get 7.5 mol.

    Hope that helps

    ahh! that helps a lot!
    thank you!!

    dont know about my chances for the exam tomorrow, though!!
 
 
 
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