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PV=NkT

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    Sanity Check

    Unit 5 - Specimen Paper Qn2.b - AQA

    Air in a bottle

    V = 3.5 x 10^-4
    P = 99kPa
    T = 291K

    How many moelcules at this temp

    PV = NkT, gets me :

    99,000 x 3.5 x 10^-4 = N x 1.38 x 10^-23 x 291

    Gets me 8.6 x 10^21 molecules

    Mark Scheme says : [they firstly get the number of moles, PV=nRT]

    Which I agree with as 1.43 x 10^-2 moles.

    Then they multiply by 6.022 x 10^-23 to get 8.6 x 10^-21

    ________________________________ ___________

    Surely they are not right are they?
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    they should have multiplied by 6.02x10^23 to get your answer
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    Yet another classic AQA blunder.
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    Ok - I was pretty sure I was right - but this is a new course just started, and as it's Unit 5, there are only two past papers, June 1020 and June 2011. So we have to use their Specimen Paper - and they can't even be bothered to double check that the stuff they churn out is right - surely if it's your job to produce these papers, you'd think they'd check them? - or at least they've had enough time to amend the mark scheme. Bad form.
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    Yeah, they've included an unnecessary '-' sign. The specimen papers are not checked or moderated as nobody has actually sat them as an exam so they're often full of errors that haven't been brought to light.

    As you obviously realised, because molecules are so small there has to be loads of them, rather than a very small fraction of a single molecule.... :rolleyes:
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    (Original post by Charries)
    Ok - I was pretty sure I was right - but this is a new course just started, and as it's Unit 5, there are only two past papers, June 1020 and June 2011. So we have to use their Specimen Paper - and they can't even be bothered to double check that the stuff they churn out is right - surely if it's your job to produce these papers, you'd think they'd check them? - or at least they've had enough time to amend the mark scheme. Bad form.
    I've been on the AQA website and I cannot find the specimen paper . A link would be much appreciated.

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Updated: May 12, 2012
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