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    Does anyone know what the highest grade boundaries for Chem 5 has been?
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    (Original post by Aethrell)
    Nah, I'm probably wrong lol

    just thought that if the left cell had say -0.3V and the right was 0.3V, the E would be 0.6V. Doubling both would give E as 1.2V

    Guessing there's some majorly wrong chemistry there though
    You don't double them. That's the point. E values aren't about the speed of the reaction, I believe

    Only similar thing I can think of is effect of catalyst on KC... speeds up reaction equally both ways= no effect. Doesn't double it
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    (Original post by hello2you)
    Does anyone know what the highest grade boundaries for Chem 5 has been?
    I just looked for june12-june 15 and highest was 84 last year. I reckon it'll be higher than that though this year.
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    (Original post by zombaldia)
    You don't double them. That's the point. E values aren't about the speed of the reaction, I believe

    Only similar thing I can think of is effect of catalyst on KC... speeds up reaction equally both ways= no effect. Doesn't double it
    Fair enough, was counting it as a dead mark anyway.

    Do you know why a higher pressure of oxygen shifted the fuel cell equilibrium is they weren't all in gaseous state?
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    (Original post by Charco63)
    Attachment 555006
    I put phase boundaries at both ends of the representation of a cell like this example in the picture 😭😭 will I lose the marks for that question?
    That's what i did? One was soIid and the other was aqueous so sure that's what it wouId be.
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    (Original post by palacefloor)
    That's what i did? One was soIid and the other was aqueous so sure that's what it wouId be.
    theyre not needed at the end
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    (Original post by Azzer11)
    I got - 67.5 because I halved my values beforehand as 2 moles of product were being formed. Standard enthalpy of formation by definition is the formation of 1 mole of a compound.

    Posted from TSR Mobile
    Units for dH are kJmol-1 so you wouldnt halve it as the value is a per molar value, also, you wouldn't halve dS because entropy change would actually be the same regardless of moles because quantity (in terms of molar quantity) is not a unit when determining entropy change for a reaction.
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    (Original post by Sniperdon227)
    theyre not needed at the end
    I don't think i incIuded the end Iines but not entireIy sure. Is it considered fuIIy wrong or couId the examiner just ignore it?
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    (Original post by rosslegg)
    Units for dH are kJmol-1 so you wouldnt halve it as the value is a per molar value, also, you wouldn't halve dS because entropy change would actually be the same regardless of moles because quantity (in terms of molar quantity) is not a unit when determining entropy change for a reaction.
    I think the case has been closed on this one.
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    (Original post by rosslegg)
    Units for dH are kJmol-1 so you wouldnt halve it as the value is a per molar value, also, you wouldn't halve dS because entropy change would actually be the same regardless of moles because quantity (in terms of molar quantity) is not a unit when determining entropy change for a reaction.

    Whats your take on this then........?

    Can someone clarify how many marks I would get for using; SO2+ 0.5O2 --> SO3 , in each question involving;
    Enthalpy: My answer was half the correct (0) marks/2
    Entropy: Since using the SO2+ 0.5O2 --> SO3 equation my entropy was also half (0 or 2 ? as follow through of error in eq) marks/2
    Gibbs: My answer was calculated using the half the correct values (follow through based on previous answers) marks/3


    Am I awarded 3/7 or 5/7 ?
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    (Original post by Azzer11)
    I think the case has been closed on this one.
    What was the consensus?
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    Is there an unofficial mark scheme or shall I try and start one? I wrote down how many marks the overall questions were worth each and I remember about 50% of it but with help it could be full.
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    (Original post by Aethrell)
    What was the consensus?
    The division of the molar ratio in the equation by 2 was the wrong method. It will most likely result in the loss of 2/3 marks.
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    (Original post by mgill17)
    Is there an unofficial mark scheme or shall I try and start one? I wrote down how many marks the overall questions were worth each and I remember about 50% of it but with help it could be full.
    Someone has already made one.

    http://www.thestudentroom.co.uk/show....php?t=4180942
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    (Original post by hello2you)
    Someone has already made one.

    http://www.thestudentroom.co.uk/show....php?t=4180942
    Great! Thanks!
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    i got -134953 Jmol-1 for delta G, is this okay?
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    i put p4o10 instead of P will i still get a mark??
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    Slighty late but when calculating Delta S and Delta H i divided by 2 is that wrong ?
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    (Original post by irendeep)
    Slighty late but when calculating Delta S and Delta H i divided by 2 is that wrong ?
    Yes. You can read the previous posts for the full explanation why
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    Can someone explain why does the E.M.F increase with pressure please? Thank you.
 
 
 
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