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    (Original post by Hamburglar)
    Personally, I just said G = -TS + H. G was plotted on the y axis, and T on the x-axis. The gradient was negative, and the y-intercept represented H. Not sure if it would score 2 marks though

    (Can't do the delta symbol, sorry).
    yh that's what I put, wasn't sure what they wanted lol!
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    (Original post by mulac1)
    ok thanks - can you remember if it was q2 or 3 ..and can you remember which compound?
    It was 3 marks, I think it was Q3
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    (Original post by dizzy17)
    yh that's what I put, wasn't sure what they wanted lol!
    Glad someone agrees

    To be honest I think they might be flexible, as long it is clear that you understand how the equations relate. Maybe one mark for recognising the gradient is negative, and one mark for relating the terms to y=mx+c? Not sure
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    (Original post by mulac1)
    Q1: a) what is the perfect ionic model (1)
    Ions are perfect spheres, only electrostatic attraction/no covalent character
    b) define 'standard enthalpy of lattice dissociation' (2)
    The standard enthalpy change to convert one mole of a solid ionic lattice into its gaseous, constituent ions
    c) Give 2 factors that affect the lattice enthalpy of dissociation (2)
    Size of the ion/ionic radius
    Charge on the ion
    d) calculate the lattice enthalpy of dissociation for AgBr (3)
    +905 kJ mol-1
    e) How would you expect your value to 1d) to differ with that calculated from the PIModel. Explain (2)
    greater;
    as there is additional covalent character/bonding

    tot = 10

    4a) What is the bonding in MgO. How could you prove that MgO has this bonding (3)
    Ionic
    Heat until molten
    Conducts electricity/gives a current when being electrolysed
    b) Why is SiO2 insoluble in water (3)
    large macromolecule
    many, strong covalent bonds
    lots of energy needed to be supplied to break bonds/ enthalpy of solution is very large
    c) What has a higher melting point - SiO2 or P4O10? Explain (3)
    P4O10 is a simple covalent molecule
    Weak VdWs (and dipole-dipole) IM forces
    Less energy needed to be supplied to break VdWs forces
    d) Write an equation to show that MgO is basic (2)
    MgO + 2HCl => MgCl2 + H2O
    e) Write an equation for the reaction of P4O10 with MgO (1)
    P4O10 + 6MgO => 2Mg3(PO4)2
    tot = 12





    5a) why can KCl not be used as a salt bridge (1)
    It is not inert/it reacts with the cell reagents/Cl- oxidized to Cl2 by Cu2+
    b) why do the electrons flow from right to left (2)
    LHS has a higher conc. of Cu2+ / LHS is positive electrode
    Equilibrium Cu2+ + 2e- => Cu lies more to right at the left hand electrode (or converse)
    c) Why does the current fall to zero after some time (1)
    Cu2+ concentration is the same in both half cells
    d) calculate the electrode potential (1)
    -3.05V
    e) Write the equation for the cell when it is being recharged (2)
    LiMnO2 => Li + MnO2
    f) Give one reason why this cell produces CO2 (1)
    CO2 released generating the electricity needed to recharge the cell
    tot = 8

    6a) calculate the frequency of visible light absorbed and state the units (2)
    4.28x10^14 s^-1 or Hz
    b) Why does this compound appear blue (2)
    d-orbital electrons absorb visible light energy and are promoted/excited to a higher energy level;
    we observe the blue colour that is not absorbed;
    c) Red/blue complex. What is the deltaE value of a red solution in comparison with a blue one? (2)
    larger;
    absorbs blue light which is of a higher frequency;
    d) State 3 factors that affect the frequency of visible light absorbed (3)
    change in…
    oxidation state
    ligands
    coordination number
    tot = 9




    7) original colours, final observation, equation for each reaction

    a) [Fe(H2O)6]2+ and [Fe(H2O)6]3+ with sodium carbonate (5 marks)
    [Fe(H2O)6]2+ = pale green solution
    observation = green ppt.
    [Fe(H2O)6]3+ = violet/yellow/brown solution
    observation = brown ppt and effervescence

    [Fe(H2O)6]2+ + CO32- => FeCO3 + 3CO2 + 3H2O
    2[Fe(H2O)6]3+ + 3CO32- => 2[Fe(OH)3(H2O)3] + 3CO2 + 3H2O

    b) [Cu(H2O)6]2+ and [Co(H2O)6]2+ with HCL (4 marks)
    [Cu(H2O)6]2+ = pale blue soln.
    observation = green/yellow soln.

    [Co(H2O)]2+ = pink soln.
    observation = blue solution

    [Cu(H2O)6]2+ + 4Cl- => [CuCl4]2- + 6H2O
    [Co(H2O)6]2+ + 4Cl- => [CoCl4]2- + 6H2O

    c) [Cr(H2O)6]3+ and [Fe(H2O)6]2+ with excess OH- (4 marks)

    [Cr(H2O)6]3+ = green or ruby soln.
    observation = green soln.

    [Fe(H2O)6]2+ = pale green soln.
    observation = green ppt.

    [Cr(H2O)6]3+ + 6OH- => [Cr(OH)6]3- + 6H2O
    [Fe(H2O)6] + 2OH- => [Fe(OH)2(H2O)4] + 2H2O

    d) [Al(H2O)6]3+ and [Ag(H2O)2]+ with excess NH3 (4 marks)
    [Al(H2O)6]3+ = colourless soln.
    observation = white precipitate

    [Ag(H2O)2]+ = colourless soln.
    observation = colourless soln/no visible change

    [Al(H2O)6]3+ + 3NH3 => [Al(OH)3(H2O)3] + 3NH4+
    [Ag(H2O)2]+ + 2NH3 => [Al(NH3)2]+ + 2H2O

    tot = 17

    8a) ethanal can be oxidised to ethanoic acid by O2. Explain why Co2+ ions can increase the rate of this oxidation. Write 2 equations showing how Co2+ does this. (4 marks)

    provides alternative mechanism/route with a lower Ea;
    as has variable oxidation states;

    2Co3+ + CH3CHO + H2O -> 2Co2+ + CH3COOH + 2H+
    4Co2+ + O2 + 4H+ -> 4Co3+ + 2H2O

    or multiples;;

    b) [Co(H2O)6] reacts with an excess of ethane-1,2-diamine. Write an equation for this reaction and explain why ethane-1,2-diamine is the more stable complex (3 marks)

    more moles of products than reactants
    Increase in disorder
    Entropy change large and positive

    [Co(H2O)6
    c) Draw the complex ion. (3 marks)

    arrows showing coordinate bonds from N atom to Co;
    octahedral arrangement;
    2+ charge;

    d) Cobalt ratio question (5 marks)
    3:1
    [Co(NH3)6]3+
    don’t know :P

    tot = 15

    [Fe(H2O)6]2+ + CO32- => FeCO3 + 3CO2 + 3H2O is wrong its:

    [Fe(H2O)6]2+ + CO32- => FeCO3 + 6H2O
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    (Original post by Hamburglar)
    Personally, I just said G = -TS + H. G was plotted on the y axis, and T on the x-axis. The gradient was negative, and the y-intercept represented H. Not sure if it would score 2 marks though

    (Can't do the delta symbol, sorry).
    But you could say all of that if the graph was a curve... I'm pretty sure they wanted some reference to the constant gradient and why.
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    (Original post by mulac1)
    yes - I didn put that in the exam ... I'm not perfect - cannot believe I was negged for that it took me ages!
    Lmfaooo haters. Bro I think you're doing a great job.
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    (Original post by mulac1)
    yes - I did put that in the exam ... I'm not perfect - cannot believe I was negged for that it took me ages!
    I didn't neg you lol..i will now though
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    (Original post by dizzy17)
    I said gradient is= to negative entropy
    Thats right!
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    The reaction was P4O10 with NaOH, not with MgO!!!!
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    (Original post by Hamburglar)
    It's just from experience that a lot of people find a paper really difficult, and boundaries don't tend to shift as much as people would think. Just don't want anyone to get their hopes up of the boundaries being super low or anything, I'm only expecting 2-3 marks of a drop Of course, I'd be happy to be wrong
    Ok. I see where you are coming from. I thought AQA had a policy of not taking into consideration how tough the paper was compared to previous ones when setting the grade boundaries. How do boards set grade boundaries?


    I would be over the moon if the boundaries are lower as both the AQA biology and Chem paper were not only bizzare but tougher than the past papers we have done. Pray that the boundaries are low as that is the only hope for us.
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    yes it was - haha I'm actually glad at that ... I thought I'd got it wrong in the exam, but in fact I've just forgotten it now..
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    (Original post by Kutie Karen)
    Ok. I see where you are coming from. I thought AQA had a policy of not taking into consideration how tough the paper was compared to previous ones when setting the grade boundaries. How do boards set grade boundaries?


    I would be over the moon if the boundaries are lower as both the AQA biology and Chem paper were not only bizzare but tougher than the past papers we have done. Pray that the boundaries are low as that is the only hope for us.

    Read this short section it will make it clearer for you:


    http://www.aqa.org.uk/news-and-polic...deo-transcript
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    How do exam boards set grade boundaries?
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    (Original post by tomj2013)
    what did people put about the y=mx+c question ? i put temp was gradient and it symbolised a negative correlation , thus negative gradient which it refers to in the equation??
    Surely deltaS was the gradient? Temperature was across the x axis
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    (Original post by Anshul91)
    Read this short section it will make it clearer for you:


    http://www.aqa.org.uk/news-and-polic...deo-transcript

    Thanks. that is great. I will read it when I feel a bit less stressed. A positive thumbs up for you for your help.
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    I think they will be somewhere in between June12 and Jan13:

    cap = 90
    A* = 82
    A = 74
    B = 66
    C = 58
    D = 50
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    (Original post by Kutie Karen)
    Thanks. that is great. I will read it when I feel a bit less stressed. A positive thumbs up for you for your help.

    no prob, basically says they get sent to external teacher who marks it by following the mark scheme. Their marking is cross checked. They then send it off to an independent panel who compare previous results, this sitting results and then decide what the boundaries should be. So if we all did bad then the boundaries should hopefully be lower.
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    can somebody draw this out c) Draw the complex ion. (3 marks)

    arrows showing coordinate bonds from N atom to Co;
    octahedral arrangement;
    2+ charge;
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    (Original post by khalidpatel)
    can somebody draw this out c) Draw the complex ion. (3 marks)

    arrows showing coordinate bonds from N atom to Co;
    octahedral arrangement;
    2+ charge;

    Its the one on the right, with a 2+ charge and its missed off the ch2 and also its NH2 but you get the idea...


    http://chemwiki.ucdavis.edu/@api/dek...ral_cobalt.png
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    (Original post by Anshul91)
    Its the one on the right, with a 2+ charge and its missed off the ch2 and also its NH2 but you get the idea...


    http://chemwiki.ucdavis.edu/@api/dek...ral_cobalt.png
    It says service temporarily unavailable
 
 
 
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