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    (Original post by Better)
    I Should really get practising then! Cheers.

    Thankfully my Chemistry Teacher has printed out 2 copies of all the past paper booklets for Chem 4 and 5. Printing in my school is so expensive.

    If anyone has access to Chem 4 and 5 Jan 2013 please inbox me! Would be much appreciated!!!
    Funny seeing you here bro! OCR physics AND chemistry. We don't have it easy do we? lol
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    (Original post by zef1995)
    Yeah I may have to! I'm intrigued :P
    It's good that you didn't find it difficult, if we get a paper like that one in the summer that would be great
    That does make sense! Fingers crossed :P
    oh I did at the time haha it was horrible, I died inside, but having done it and looking back it was hard, and more doable than I thought -yes some very hard bits, but most people could have got like 3/6 or 4/6 if you do working and remember the basic principles!
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    (Original post by awilson008)
    Funny seeing you here bro! OCR physics AND chemistry. We don't have it easy do we? lol
    Hahaha! Mate it will pay off in the end !
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    (Original post by awilson008)
    That would be insane! I think I'm gradually getting better after each paper I do, so will have to try my hardest to get near that.

    Anyway yeah I did it as a mock, but not with my class. I just did it at home. I could hardly get it done in the time constraints and some of the questions took me ages to figure out, but it was my first past paper for F325. What about you?
    It certainly would be! That's great to hear, if you're constantly improving that's a good sign

    Ah fair enough, I'm guessing you did it under times conditions and everything? It seems like a good one to do as a mock, as it was a challenging paper and you could practice time pressure too. I know what you mean though, 2 hours sounds like a long time but it goes so fast! At least it was your first paper, there are plenty more papers you can do over time to practice time management, exam technique etc I've done a couple of papers so far (June 10, Jan and June 11, and Jan 13), but I'm hoping to use the 2012 papers as mocks during the half term!

    (Original post by MedMed12)
    oh I did at the time haha it was horrible, I died inside, but having done it and looking back it was hard, and more doable than I thought -yes some very hard bits, but most people could have got like 3/6 or 4/6 if you do working and remember the basic principles!
    Haha, I know what you mean, at the time things usually look worse than they actually are :P I agree with you, it wasn't an easy paper, but if you remember the basic principles you could definitely work through the questions logically Like the lat question, I had no idea how to get the answer but managed to pick up a few marks by using the data given to do some calculations!
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    Hey, guys i'm also resitting this exam, i'm guessing the exam can't be any harder than January's so hoping for the best
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    (Original post by JimmyA*)
    Hey, guys i'm also resitting this exam, i'm guessing the exam can't be any harder than January's so hoping for the best
    Good luck!
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    Thanks, same to you, I made so many stupid mistakes and knowing that only 2 more marks would of got me an A makes it all the worse
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    Has anybody got any "Stretch and Challenge" questions so that I can practice the higher-level questions.
    Jan 13 paper has left me rather worried!
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    (Original post by Gulzar)
    I got 247 but a D in f324 so need to retake and aim for that A
    we can do this!
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    I don't suppose someone could tell me what sodium thiosulphate does to iodine as I've seen it a large portion of questions and I'm still not quite sure what happens that we can observe :-/


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    someone is on a neg hype
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    (Original post by MathsNerd1)
    I don't suppose someone could tell me what sodium thiosulphate does to iodine as I've seen it a large portion of questions and I'm still not quite sure what happens that we can observe :-/


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    I remember seeing it in the textbook. can't remember at the top of my head. Glad you mentioned this, as looks like I'll need to cover it
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    (Original post by MedMed12)
    I remember seeing it in the textbook. can't remember at the top of my head. Glad you mentioned this, as looks like I'll need to cover it
    Yeah, it's came up about 5-6 times already as I've been going through questions from relevant sources according to my teachers anyway, I'll have a look in a minute after marking the mock I've just done for unit 1


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    Can anyone explain to me what happens at which terminal of a hydrogen-oxygen fuel cell when an alkaline electrolyte is used?

    This is what I understand so far of what happens in a fuel cell with an acid electrolyte:
    - At the anode the platinum catalyst splits the H2 into protons and electrons.
    - The H+ crosses the electrolyte membrane, forcing the e- to travel around the circuit to the cathode (creating an electric current).
    - At the cathode, O2 combines with the H+ from the anode and the e- from the circuit to make H2O.

    So, at the anode: H2 --> 2H+ + 2e-
    And at the cathode: 1/2O2 + 2H+ + 2e- --> H2O

    Please please please help me I'm a little confused
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    (Original post by Aliceo)
    Can anyone explain to me what happens at which terminal of a hydrogen-oxygen fuel cell when an alkaline electrolyte is used?

    This is what I understand so far of what happens in a fuel cell with an acid electrolyte:
    - At the anode the platinum catalyst splits the H2 into protons and electrons.
    - The H+ crosses the electrolyte membrane, forcing the e- to travel around the circuit to the cathode (creating an electric current).
    - At the cathode, O2 combines with the H+ from the anode and the e- from the circuit to make H2O.

    So, at the anode: H2 --> 2H+ + 2e-
    And at the cathode: 1/2O2 + 2H+ + 2e- --> H2O

    Please please please help me I'm a little confused
    Do we need to know what happens with an alkaline electrolyte? :-/


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    (Original post by MathsNerd1)
    Do we need to know what happens with an alkaline electrolyte? :-/
    I'm not sure - but in the main OCR chemistry textbook they use an alkaline electrolyte as an example (but I didn't understand the explanation), and in the CGP textbook they use an acid electrolyte (which I understood). So do you think it's okay if we just know one or the other?
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    (Original post by Aliceo)
    I'm not sure - but in the main OCR chemistry textbook they use an alkaline electrolyte as an example (but I didn't understand the explanation), and in the CGP textbook they use an acid electrolyte (which I understood). So do you think it's okay if we just know one or the other?
    Hmm, if its in the textbook I'll say that there's a possibility of it appearing in the exam :-/


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    Also, does anyone have any advice/links that will help me understand how to write ionic equations and full equations? I know this is meant to be really basic stuff, but I still struggle and make little mistakes here and there... And I always seem to guess what state symbols to use! D:
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    (Original post by MathsNerd1)
    Hmm, if its in the textbook I'll say that there's a possibility of it appearing in the exam :-/
    Great... And it just happens to be the one I don't understand! I really like how the CGP book breaks it down and actually explains it, whereas the main textbook just gives the equations and that's it. Suppose I'll just have to memorise them
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    (Original post by Aliceo)
    Also, does anyone have any advice/links that will help me understand how to write ionic equations and full equations? I know this is meant to be really basic stuff, but I still struggle and make little mistakes here and there... And I always seem to guess what state symbols to use! D:
    Okay I've just had a look at the book and it looks like they're both used, the PEM is an acidic one whereas the book is an alkaline one, which if you think about it makes some sense as the OH- ions are passing through instead of the H+ ions that pass through in the acidic one to react with the H+ ions formed at the negative terminal.

    Also I always remember in aq things are represented as ions which then can cancel off if they're spectator ions and solids can't be split into their ions


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