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    sorry to interrupt, but does anyone have the specimen mark scheme for this F335 exam? i'm actually not sure if it exists..

    thanks
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    (Original post by I'mBadAtMaths)
    How is everyone finding the course so far? If you've finished the course, how are you revising?

    I've pretty much finished the course, so next week I'll be working through Chemical Storylines. wooooooop.

    How I revise Chemistry:

    - Work through storylines, reading through it and doing the assignments
    - When any Chemical Ideas pop up that it tells you to do in Storylines, I go through them, making notes and then do the questions
    - Read through CGP, and learn the practical techniques (GLC, recrystallisation, etc...)
    - Learn the organic reactions
    - Do all of the past papers

    Seems to work, I'm doing pretty well so far.
    Do we have to know all the practical techniques for F335?
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    (Original post by SmileyGurl13)
    Do we have to know all the practical techniques for F335?
    Yes. Could ask you about any of them.
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    Is anybody able to explain how the ocean acts as a carbon dioxide buffer?

    I've been working through chemical storylines and the revision guide but I still can't quite get my head around it. How would you explain this in a concise way if a question were to come up?
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    (Original post by creme.egg)
    sorry to interrupt, but does anyone have the specimen mark scheme for this F335 exam? i'm actually not sure if it exists..

    thanks
    F335_Specimen Paper.pdf

    Here you go mate and its from page 21 me think.
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    Thank you so much!
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    (Original post by creme.egg)
    Thank you so much!
    no problem
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    Dreading this exam!
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    (Original post by MyJunkIsYou)
    Is anybody able to explain how the ocean acts as a carbon dioxide buffer?

    I've been working through chemical storylines and the revision guide but I still can't quite get my head around it. How would you explain this in a concise way if a question were to come up?
    I doubt we would be asked a question EXACTLY like that. All I think we need to remember is how buffers work and apply it to oceans.

    How buffers work
    Buffers are made from either a weak acid and one of its salt
    The salt completely dissolves in water to create a proton acceptor and an ion

    When a small amount of acid or alkali is added, it reacts with the salt.

    What happens in the ocean

    When CO2 dissolve in the ocean, carbonic acid is made (H2CO3), this then splits into 2H+ and CO3(2-)

    The salt in the ocean in Calcium Carbonate, when this dissolves in water, it creates CO3(2-). This CO3(2-) sweeps up any extra H+

    I hope that made SOME sense
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    (Original post by tkoki1993)
    I doubt we would be asked a question EXACTLY like that. All I think we need to remember is how buffers work and apply it to oceans.

    How buffers work
    Buffers are made from either a weak acid and one of its salt
    The salt completely dissolves in water to create a proton acceptor and an ion

    When a small amount of acid or alkali is added, it reacts with the salt.

    What happens in the ocean

    When CO2 dissolve in the ocean, carbonic acid is made (H2CO3), this then splits into 2H+ and CO3(2-)

    The salt in the ocean in Calcium Carbonate, when this dissolves in water, it creates CO3(2-). This CO3(2-) sweeps up any extra H+

    I hope that made SOME sense
    Am I therefore correct in saying that if small amounts of acid are added to the oceans, then the extra H+ ions react with the CO3 (2-) produced by the salt forming more H2CO3 and hence shifting the equilibrium position to the left. If small amounts of alkali are added then the H2C03 dissociates further producing more 2H+ and CO3(2-) shifting the equilibrium to the left. This helps to maintain the PH of the oceans.
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    What's the specimen paper for?
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    (Original post by SmileyGurl13)
    Do we have to know all the practical techniques for F335?
    Yes. However their prefered questions are on GLC as a practical technique.
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    (Original post by Cinamon)
    Dreading this exam!
    Same. I think I'm dreading it more because there is absolutely no chance for a resit more than anything else.
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    (Original post by limetang)
    Yes. However their prefered questions are on GLC as a practical technique.
    Can they ask to draw any experiments out e.g reflux or distillation?

    Can some one cover all the main experimental techniques we require for this exam?
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    (Original post by ManPowa)
    Can they ask to draw any experiments out e.g reflux or distillation?

    Can some one cover all the main experimental techniques we require for this exam?
    Yes they can and have asked questions about reflux, although to be honest most of the questions on reflux are either a two mark what is it. To which you would say something like: It's a method of heating the reaction mixture with a vertical condenser attatched to prevent loss of product. And the diagrams they may ask you to learn involve drawing and labelling the pear shaped flask the vertical condenser the anti bumping granuels reactants etc.

    Recrystalisation:
    Dissolve in minimum amount of hot solvent.
    Filter to remove insoluble impurities.
    Allow to cool and allow crystals to form.
    Perform vaccum filtration and wash the crystals with the minimum amount of cold solvent.
    Allow to dry.

    Thin layer chromatography: (Mostly in the diagram)
    Draw a chromatography plate with a base line drawn on. Spots of your sample labelled. Solvent front labelled. Draw dots spreading out. Have it in a beaker with the mobile phase bellow the base line. Have the beaker covered.

    GLC:
    Column. High Boiling point liquid. Inert carrier gas. Detector.

    Those are my rough guides to the experimental techniques anyway (not sure I've got them all in)

    DO NOT PANIC about drawing diagrams though. Just make sure you label everything of significance and you will get most of the marks (if not all)
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    (Original post by zahre)
    Am I therefore correct in saying that if small amounts of acid are added to the oceans, then the extra H+ ions react with the CO3 (2-) produced by the salt forming more H2CO3 and hence shifting the equilibrium position to the left. If small amounts of alkali are added then the H2C03 dissociates further producing more 2H+ and CO3(2-) shifting the equilibrium to the left. This helps to maintain the PH of the oceans.
    YUP
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    (Original post by jpurkis1)
    F336?
    37 raw marks out of 45 is 82%...or an A...:confused:
    http://www.ocr.org.uk/download/admin...und_jun_10.pdf
    37 was minimum for an A last year, it seems the grade boundaries are creeping UP year on year, therefore I'm taking it as a B. Not to mention my whole class is being moderated, as there's only ten of us. So the odds are against me getting an A in F336!

    (Original post by Dandan10)
    I think the storylines are pretty useless..........
    There's a decent bit on the buffering effect that the oceans have, apart from that, yeah, pretty useless, especially as even if you did the assignments there's no way to mark them, and my teacher has picked up several mistakes in answers, i just SKIM majorly to the most important bits, the OCR revision guides identifies these bits
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    (Original post by tkoki1993)
    YUP
    Thanks for confirming.
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    I thought the practical techniques were only for F334 I haven't seen them in any past papers for F335 but please correct me if I'm wrong!!
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    I'm bricking it. I think I need 159/210 marks between F335 and F334 (we were advised to take them both in June) to get a B overall which I will need for my firm.

    What the hell can I do?! I've almost finished reading everything in CI for F335, then plan to just do past papers all day every day until the exam. I don't know how I'm going to remember the toolkit either
 
 
 
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