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    (Original post by INeedToRevise)
    Hmm, I liked the June 2010 paper and that was pretty low boundaries like 71 for an A. I think something like that would be good.

    Dont even mention F324 haha :sad:. I'm gonna have to cram like crazy on wednesday evening and thursday.
    Same here, i really liked June 2010, whereas Jan 2011 :grumble:. As long as theres no big marker on a calculation, but knowing my luck there probably will be . I havent looked at it since easter if im honest, im putting it off cus' i think i'll do ok on that one, but hey i might just end up crying the night before :sigh:.
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    This has probably been asked on here 100 times, but does anyone have the A2 exam cafe answers from the book? Our school doesnt give us the cds
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    (Original post by blush.ox)
    Same here, i really liked June 2010, whereas Jan 2011 :grumble:. As long as theres no big marker on a calculation, but knowing my luck there probably will be . I havent looked at it since easter if im honest, im putting it off cus' i think i'll do ok on that one, but hey i might just end up crying the night before :sigh:.
    I haven't done Jan 2011 yet. Leaving it as a proper mock once I feel as ready as I could ever be. I heard its really bad, grade boundaries were very low as well.
    I don't mind calculations on rates/energy. Its just the moles and redox stuff I get messed up on. Just gonna do loads of questions I guess. I've been working through this huge past paper booklet. 72 questions out of 126 :boring: Gonna move on to some biology now.
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    I need some general help with noticing what state symbols to use for equations >< . FOr example, there was a question which asked me to write down the full and ionic equations for some acid-base reactions, including:
    1) Hydrochloric acid and solid calcium carbonate
    2) Nitric acid and magnesium oxide

    1) Easy enough, acid is obviously (aq) and CaCO3 was stated as (s).
    2) Acid is (aq) but they didn't actually 'state' the state for Magnesium Oxide, so it got me there.. I took a guess that it was solid, but how do I know for sure? If it were aqueous I would have had the entire answer wrong!
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    (Original post by ViralRiver)
    I need some general help with noticing what state symbols to use for equations >< . FOr example, there was a question which asked me to write down the full and ionic equations for some acid-base reactions, including:
    1) Hydrochloric acid and solid calcium carbonate
    2) Nitric acid and magnesium oxide

    1) Easy enough, acid is obviously (aq) and CaCO3 was stated as (s).
    2) Acid is (aq) but they didn't actually 'state' the state for Magnesium Oxide, so it got me there.. I took a guess that it was solid, but how do I know for sure? If it were aqueous I would have had the entire answer wrong!
    According to my text book, Magnesium Solid reacts with the nitric acid to give Mg(NO3)2 + H20. I'm not entirely sure whether it works for all acid base reactions. I'm thinking a wrong state symbol wouldn't be worth more than a mark, so it wouldnt be absolutely the end of the world. If that helps.
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    I hate fuel cells with a passion, its just lots of remembering -.-
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    struggled with chemistry for the 2 years and always just scrapped my A. Why am I finding this one easy????? anyone else? I feel like I'm missing something
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    (Original post by jbrown42)
    This has probably been asked on here 100 times, but does anyone have the A2 exam cafe answers from the book? Our school doesnt give us the cds
    RES12_chem_book_answers.pdf:
    Your file of 1.89 MB bytes exceeds the forum's limit of 976.6 KB for this filetype.

    blast
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    does anyone have the jan 2010 f325 ocr past paper and mark scheme ?
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    when do you not need to use a platinum catalyst?
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    can someone also explain to me ionic size and charge for lattice enthalpies with examples please?
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    (Original post by INeedToRevise)
    Hmm, I liked the June 2010 paper and that was pretty low boundaries like 71 for an A. I think something like that would be good.

    Dont even mention F324 haha :sad:. I'm gonna have to cram like crazy on wednesday evening and thursday.
    Haha i'll join you with the cramming!!!! I have psychology on the 21st so spending the 6 days doing psychology. done absolutely nothing 'cos im too traumatized about biology and chemistry.. after 21st its major cramming! Ive done benzene (first topic).. quite proud.
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    (Original post by Rosi M)
    Haha i'll join you with the cramming!!!! I have psychology on the 21st so spending the 6 days doing psychology. done absolutely nothing 'cos im too traumatized about biology and chemistry.. after 21st its major cramming! Ive done benzene (first topic).. quite proud.
    Yeah, I have psychology on the 21st as well, thats going to be cramming as well except I have biology the next day :cry2: so the evening of the 21st is definitely gonna be cramming for biology. After that its all chemistry.
    Thats good I should do that. I quite like benzene haha
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    (Original post by volvicstar)
    when do you not need to use a platinum catalyst?
    when there is no metal eg. the half cell sn4+/sn2+ needs platinum electrode otherwise it cannot complete the circuit to produce a voltage however Cu2+/Cu doesn't need a platinum electrode as you can simply connect the circuit up the copper.
    (Original post by volvicstar)
    can someone also explain to me ionic size and charge for lattice enthalpies with examples please?
    To put it simply:

    A larger charge = larger lattice enthalpy as the electrostatic attraction will be stronger. eg AlCl3 will have a greater lattice enthalpy than MgCl2 as the charge on Al is 3+ compared to Mg which is 2+


    Smaller size = larger lattice enthalpy as the ions are closer together so they exert a greater force.

    eg. MgCl2 will have a greater lattice enthalpy than MgBr2 since the Br ion is much larger

    hope this helps.

    EDIT: why the negs? :confused:
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    Hi,

    I was working through a pack of questions from my teacher on unit 2. The question was from jan 2009 trends and patterns (old spec) past paper and I'm not sure if she has accidently included it or if my answer is wrong for a reason:

    The question is: Explain why magenesium carbonate decomposes at a much lower temp than barium carbonate.

    My observation is that magnesium and barium have the same ionic charge but barium has a greater ionic radius than magnesium and therefore the electrostatic attraction between oppositely charged ions in the magnesium is greater as the ionic radius is smaller so ions pack closer together.

    Therefore I would think that you would need more energy, and hence a higher temperature to break down the ionic lattice which is stronger (magnesium) and not less temperature as the question suggests.

    Is this just a case of an old question including concepts that we don't need to know about or am I making an error.
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    (Original post by hiyarearl)
    Hi,

    I was working through a pack of questions from my teacher on unit 2. The question was from jan 2009 trends and patterns (old spec) past paper and I'm not sure if she has accidently included it or if my answer is wrong for a reason:

    The question is: Explain why magenesium carbonate decomposes at a much lower temp than barium carbonate.

    My observation is that magnesium and barium have the same ionic charge but barium has a greater ionic radius than magnesium and therefore the electrostatic attraction between oppositely charged ions in the magnesium is greater as the ionic radius is smaller so ions pack closer together.

    Therefore I would think that you would need more energy, and hence a higher temperature to break down the ionic lattice which is stronger (magnesium) and not less temperature as the question suggests.

    Is this just a case of an old question including concepts that we don't need to know about or am I making an error.
    I hope we don't need to know that either it comes up loads in the legacy spec and I don't really understand it , check this out it helps a bit.
    http://www.chemguide.co.uk/inorganic...thermstab.html
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    (Original post by Killmepls)
    I hope we don't need to know that either it comes up loads in the legacy spec and I don't really understand it , check this out it helps a bit.
    http://www.chemguide.co.uk/inorganic...thermstab.html
    Ah right so it's mainly an old-spec thing, fair enough. I doubt we'll need to know it because it isn't in the text book.
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    Just marked the specimen paper... Hate it with a passion! This paper is so finicky with the wording. I guess I just have to learn to read the effing question!!
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    (Original post by student777)
    Just marked the specimen paper... Hate it with a passion! This paper is so finicky with the wording. I guess I just have to learn to read the effing question!!
    There are so many mistakes in the specimen paper. And our paper is not going to be like that at all. There is hardly any application in that paper. :sigh:
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    (Original post by INeedToRevise)
    There are so many mistakes in the specimen paper. And our paper is not going to be like that at all. There is hardly any application in that paper. :sigh:
    past papers are useful...but it is better to know your textbook content inside out...applying your knowledge to the questions is what they're mostly basing the A2 papers upon...although the calculations are pretty much so relevant from the old papers!
 
 
 
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