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    3 exams left. I can almost taste the freedom. We can do this.
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    (Original post by alongcamelucy)
    How is everyone learning all the transition metal colours / substitution reactions etc? Any tips?
    I'm just staring at a piece of paper with them all on and hoping they go in.

    I'm trying to make little things to help me like
    Copper is mostly blue
    Fe2+ is always green
    CoCO3 it's like CoCO chanel, which is girly so pink
    For Co3+ it's brown/dark brown
    For all of Cr3+ it's green except for NH3 which is purple. Idk why but I always think NH3 sounds posh and like purple is a regal colour. Idek why
    Cr6+ is orange/yellow and like in the map I've drawn they're at the top like the sun, then Cr2+ is at the bottom which is blue like the sea

    After typing this out I have realised how ****ing weird I am
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    Thank you!
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    Hey guys pretty confused on 7bii of the jan 11 paper, were told h202 is reduced to OH- ions, therefore the cr3+ ions have been oxidised to cr+6 but i dont understand how you find the 2nd half equation, is it because you balance the 3e-s on the right first to deal with the oxidation state change then balance the charges by adding OH- to the left then the h2o's on the right?


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    (Original post by poopnoddy)
    Hey guys pretty confused on 7bii of the jan 11 paper, were told h202 is reduced to OH- ions, therefore the cr3+ ions have been oxidised to cr+6 but i dont understand how you find the 2nd half equation, is it because you balance the 3e-s on the right first to deal with the oxidation state change then balance the charges by adding OH- to the left then the h2o's on the right?


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    Not sure which half equation you're on about, but I'd just do it like this

    H2O2 + 2e- \rightarrow 2OH-
    [Cr(OH)6]3- \rightarrow CrO42- + 2H2O + 2H+ + 3e-

    Then combine them:
    2[Cr(OH)6]3- + 3H2O2 \rightarrow 2CrO42- + 4H2O + 4H+ + 6OH-

    The four H+ ions combine with four of the OH- ions, meaning the equation can be simplified to:
    2[Cr(OH)6]3- + 3H2O2 \rightarrow 2CrO42- + 8H2O + 2OH-
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    I keep reading Cu/Co/Cr wrong in practice questions and getting them mixed up. Time to call it a day with revision I think.
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    You know for the june 2012 calculation...I'm getting more than 100%
    I'm going to cry
    K bye
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    (Original post by loknath)
    You know for the june 2012 calculation...I'm getting more than 100%
    I'm going to cry
    K bye
    I think the answer is right though, it was an examiner's cockup. Or something like that. Either way a lot of people were WTFing at that last year.
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    (Original post by loknath)
    You know for the june 2012 calculation...I'm getting more than 100%
    I'm going to cry
    K bye
    Your ratio from part i is probably wrong. The mark scheme says a ratio of 3:7 or 2:5 can give an answer of more than 100%. You still get full marks for part ii though because its error carried forward
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    (Original post by failingatm)
    I think the answer is right though, it was an examiner's cockup. Or something like that. Either way a lot of people were WTFing at that last year.
    No the right answer was 93.4% but they do accept loads of different answers so you could be right about some sort of cockup :confused:
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    (Original post by crc290)
    No the right answer was 93.4% but they do accept loads of different answers so you could be right about some sort of cockup :confused:
    Ahh right. Well I just remember people coming out of the exam all going on about the answer being more than 100%

    I know last years paper wasnt very popular after the exam
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    (Original post by failingatm)
    Ahh right. Well I just remember people coming out of the exam all going on about the answer being more than 100%

    I know last years paper wasnt very popular after the exam
    It was a weird question. I've never seen one on any other past paper where you have to combine 3 half equations, so I guess the examiners were giving people the benefit of the doubt
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    (Original post by crc290)
    It was a weird question. I've never seen one on any other past paper where you have to combine 3 half equations, so I guess the examiners were giving people the benefit of the doubt

    I HAD A 2:5 RATIO
    NO JOKE THIS IS THE HAPPIEST IVE BEEN ALL DAY
    high on coffee sorry
    I think I just ate dog treat no it was a chocolate button
    I'm going mental. Dayum.
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    (Original post by loknath)
    I HAD A 2:5 RATIO
    NO JOKE THIS IS THE HAPPIEST IVE BEEN ALL DAY
    high on coffee sorry
    I think I just ate dog treat no it was a chocolate button
    I'm going mental. Dayum.
    :laugh:

    Well I bet you're glad you'd only lose 1 mark and not 6

    The actual ratio is 3:5 though...
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    (Original post by crc290)
    :laugh:

    Well I bet you're glad you'd only lose 1 mark and not 6

    The actual ratio is 3:5 though...
    I'm confused? What's with the 2:5 thing? Is it do do with carry over marks? I.E you only lose the accuracy mark? Because I don't see where the ****-up is
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    (Original post by frogs r everywhere)
    3 exams left. I can almost taste the freedom. We can do this.
    what exams have you done already and how did they go?
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    (Original post by loknath)
    You know for the june 2012 calculation...I'm getting more than 100%
    I'm going to cry
    K bye
    Aqa made an error on that paper. Do not use the mole ratio they provide. It's 3:5, not 3:7.
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    Anyone else struggling to focus on chem with bio coming up?
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    (Original post by Chris-69)
    I'm confused? What's with the 2:5 thing? Is it do do with carry over marks? I.E you only lose the accuracy mark? Because I don't see where the ****-up is
    Aqa cocked up. They provided an incorrect mole ratio. Cause they are so clever they did not bother to check.
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    (Original post by SexyAndIKnowIt.)
    Do we have to know about silver/ silver chloride, calomel, zinc/ carbon and lithium ion electrodes or do we just have to know them as examples of whatever.
    If so - what are they all used for,, don't know anything on the above 4 electrodes so if we have to know anything about them, I would appreciate some guidance thanks x
    You might have already got your answer but in my notes I have this section (attached also):

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