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    (Original post by Gulzar)
    Mistake....Co(OH)2 is a blue precipitate
    Thought it went blue/green then pink.
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    (Original post by eggfriedrice)
    Thought it went blue/green then pink.
    starts off a pink solution then forms a blue precipitate. then it turns beige in air.
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    (Original post by needtosucceed=))
    starts off a pink solution then forms a blue precipitate. then it turns beige in air.
    Ah. So the revision guide is wrong?
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    (Original post by eggfriedrice)
    Ah. So the revision guide is wrong?
    does it say a green precipitate is formed?!
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    (Original post by needtosucceed=))
    does it say a green precipitate is formed?!
    No, it says it goes blue/green then pink :s I'm confused now. I looked online and different sources say pink, blue or brown. -_-
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    (Original post by eggfriedrice)
    No, it says it goes blue/green then pink :s I'm confused now. I looked online and different sources say pink, blue or brown. -_-
    cgp revision guide?
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    (Original post by needtosucceed=))
    cgp revision guide?
    No, OCR.

    http://www.amazon.co.uk/dp/043558374..._df_0435583743
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    (Original post by eggfriedrice)
    Thought it went blue/green then pink.
    It goes from pink to form a blue precipitate as already stated. The textbook actually says this in a little table if you look at page 207


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    (Original post by sidmanny)
    Hi there's a question which I'd love some help with -
    In drinking water the OH- concentration is 100 times greater than the H+ concentration. What is the pH of this drinking water?

    The answer is 8 but I don't understand how you get there, any help please?
    Hi, I was thinking about this question. First I got out the ionic product of water equation, rearranged, got 16 (assuming Kw is 1 x 10^(-14) at 25'C).

    So not right. Now I think, well actually, what is it actually asking? In water, you can't have OH- conc. being 100 times more than the H+ conc. Otherwise it's not water, it's OH- ions dissolved in water. H2O dissociates to H+ + OH-, that's why it's neutral.

    So I did finally get 8, but I needed a-level maths ability, manipulating logs to get there. I doubt that'd ever be in the exam. I'll show you now if you like.

    [OH-] = 100 x [H+] (given in the question)
    therefore pOH = -log (100 x [H+])

    pH = 14 - pOH

    therefore
    -log[H+] = 14 - (-log (100 x [H+]))
    -log[H+] = 14 + log(100[H+])
    -log[H+] = 14 + 2 + log[H+] (log laws)
    -2log[H+] = 16
    -log[H+] = 8
    pH = 8
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    (Original post by MathsNerd1)
    It goes from pink to form a blue precipitate as already stated. The textbook actually says this in a little table if you look at page 207


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    Aha that's true. Must be a misprint in the revision guide. -_-
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    (Original post by eggfriedrice)
    Aha that's true. Must be a misprint in the revision guide. -_-
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    Yeah that looks like a misprint alright, which book is this exactly?


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    In Fuel cells, is it always the case that the hydrogen (or hydrogen fuel) is oxidised?
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    (Original post by MathsNerd1)
    Yeah that looks like a misprint alright, which book is this exactly?


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    This one.
    It's the one that goes with the text book.
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    (Original post by eggfriedrice)
    This one.


    It's the one that goes with the text book.
    I see, I have the CGP one which isn't too bad really, better get back to revision now


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    A question guys;
    If you're asked to sketch a concentration against time graph, will the bottom end of the end touch the x axis or just tend towards it?
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    Is Cr (VI) orange and Cr (III) yellow? If so do we need to know this, it's cropped up in the really old papers before but I'm confused. I always thought Cr (III) was green
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    (Original post by MathsNerd1)
    Well there was clearly no need for this comment, if you didn't care then why even reply to my message? It's not like i asked for someone to reply to it. Now I'm going to civil about this and just move on, next time please have some respect and be polite when posting comments.


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    You posted it on a forum so yes, you probably did expect a reply and you got one.

    (Original post by Better)
    Would love to meet someone like you in person. No one is ever as confident in person as they are on the internet.

    Do you even lift bro?

    But let's just keep focused on the Chemistry the exam is in 2 days. Please just try to stop making arrogant remarks every time someone says something you've done it like 5x already.

    With a family of people in Medicine your Arrogance was probably why you didn't get into Medical School; so please, stop being a douche.
    I'm sure you have and will get great grades, but you're probably best off doing Biomedical Science - a subject with careers which require less human contact.
    I'd be confident enough to confront you.
    Actually, the reasons which didnt get in: 1)Not enough extra cirrculuar interests. 2) Time management.
    So stfu.
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    Anyone can work out the number of moles of O2 in:
    Jan 2011: 7(a)(i)?
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    (Original post by DudeBoy)
    It's good man, make sure you get it right in the exam
    yeah i get all that but what does the hydrogen electrode actually look like when you draw it out?
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    (Original post by JP.)
    Is Cr (VI) orange and Cr (III) yellow? If so do we need to know this, it's cropped up in the really old papers before but I'm confused. I always thought Cr (III) was green
    (cr207)2- is orange and cr3+ is green
    Its in f324. So id probably remember them
 
 
 
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