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    2marks for equation !



    (Original post by FireBLue97)
    Lets get this straight
    1 mark for equation 2:5 ratio
    2nd mark for no of moles of Mno4- 0.02x(26.4/1000)
    3rd mark for finding moles of C2o4- using the ratio 0.00132
    4th mark for x10 to find in original 250 cm3
    5th mark for x by 88 Mr of C2O4 to get 1.16 as this is specifically for the total C2o4 present before titre so up to this point definitely right
    6th mark for the Mr of C2o4 which is 88
    7th mark for dividing by 2.29 or something then times 100% to get the percentage as 50.7
    Here are the official 7 marks for this question as both the 50.7 and 94.4% answers concern C2o4 pressent in the original sample 94.4 gives 8 marks whilst this is a 7 marker so why isnt this paper out of 101 dalmations
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    (Original post by palacefloor)
    Was there a question about advantage and disadvantage?? I don't remember that at aII?
    It was the last question of the fuel cell one! 'What is the main environmental advantage of fuel cells' or something
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    How many marks do you reckon I'll lose for not dividing the enthalpy/entropy equation by 2? I think there were 6 marks available, not sure. The question with SO2 and SO3

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    (Original post by chloeabeki)
    Would I lose marks for not having my coordinate bonds as arrows? I drew them like normal covalent bonds and now I'm kicking myself!
    I've only seem them award marks in the past for arrows when they ask you to 'show the bonding' in the complex - I can't remember if they did.

    You might be OK though.

    (Original post by Ginpls)
    It was the last question of the fuel cell one! 'What is the main environmental advantage of fuel cells' or something
    I said they don't need to be electrically recharged but apparently it's that they don't produce CO2

    However the last part of that question was about them not being carbon-neutral.
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    (Original post by Fibsy)
    How many marks do you reckon I'll lose for not dividing the enthalpy/entropy equation by 2? I think there were 6 marks available, not sure

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    We don't know for sure if you do or don't, BUT the main consent is that you DO NOT.

    Regardless, it would be a mark lost for each calculation from that equation (so -2 marks) since Gibbs uses error carried forward.
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    http://www.thestudentroom.co.uk/show....php?t=4180942
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    (Original post by Suits101)

    I said they don't need to be electrically recharged but apparently it's that they don't produce CO2

    However the last part of that question was about them not being carbon-neutral.
    My bad, meant second to last question*
    Yeah its either acid rain or no co2 emission as the question said 'environmental advantages'
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    Guys for the Lattice dissociation question did you have to times the 90 which was atomisation of K by 2??
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    If my reaction was endothermic do I get follow through marks for correct explanation?
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    (Original post by Ginpls)
    My bad, meant second to last question*
    Yeah its either acid rain or no co2 emission as the question said 'environmental advantages'
    Last question is referring combustion of fossil fuels releasing CO2

    (Original post by Anam)
    Guys for the Lattice dissociation question did you have to times the 90 which was atomisation of K by 2??
    Yes.
    (Original post by emma_1111)
    If my reaction was endothermic do I get follow through marks for correct explanation?
    Normally do
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    You know what I think there was another one of AQAs infamous typos the question was supposed to say standard enthalpy and instead they put enthalpy by accident so it means that this question will probably be free marks for everyone who has either put the 135 or the 62.5 hopefully
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    (Original post by Suits101)
    Last question is referring combustion of fossil fuels releasing CO2



    Yes.

    Normally do
    (Original post by Suits101)
    Last question is referring combustion of fossil fuels releasing CO2



    Yes.

    Normally do
    Is that all you had to do? I got 1910kjmol-1 or something
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    (Original post by FireBLue97)
    You know what I think there was another one of AQAs infamous typos the question was supposed to say standard enthalpy and instead they put enthalpy by accident so it means that this question will probably be free marks for everyone who has either put the 135 or the 62.5 hopefully
    You think or know? Haha.
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    (Original post by Anam)
    Is that all you had to do? I got 1910kjmol-1 or something
    Multiply atomisation and ionisation enthalpies of K by 2
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    (Original post by gh2)
    Ahh fair enough i do see :/. However for the reaction you had 2 moles of SO2/SO3, therefore when you do the eqtn, in terms of units, a 'KJ mol-1' is multiplied by 'mol' (the 2 as there are 2 moles of SO3/SO2) therefore delta H is in KJ but for one mole you divid by 2 again to get KJ mol-1? sorry for complex stuff
    Sorry that's not how to derive units in equations, coefficients are completely irrelevant in this and all cases when it comes to units so it is still kJ mol-1

    I only realise that people quoting 'you have to divide by two' were referring to an example of the standard enthalpy of formation
    Yes, if it was the standard enthalpy of formation of course you would divide by two, but it's not. It's delta H reaction, and so actually dividing by 2 is incorrect, because frankly it's wrong. There's only one value for delta G of this reaction, I don't see any reason for AQA to accept an incorrect value. Plus, for any complaining that they worded it weirdly, there is no logical chemistry argument to justify dividing by 2
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    (Original post by User2334541)
    Yeah, just realised that I made a tiny mistake, forgot to remove 4s first due to lower energy compared to the 3d... :/
    Pretty sure its 3d5 cuz in that state theres one electron in each orbital and it means its in its most stable form
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    Can someone please explain to me why the emf would increase if pressure of oxygen increases? Thanks!
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    (Original post by Suits101)
    Multiply atomisation and ionisation enthalpies of K by 2
    I only multipled the 90 by 2 how many marks lost?
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    (Original post by Anam)
    I only multipled the 90 by 2 how many marks lost?
    It was only 2 marks.

    Maybe both? One if you're lucky because cycle was given.
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    Why a small pellet of vanadium used?
 
 
 
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