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    yep thanks
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    Grade boundary predictions? Lol why is everyone ignoring my comments x

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    (Original post by mulac1)
    no - the 2nd page of question 8
    Sorry about that my brain is a bit tired and not entirely functioning! its been a busy couple of weeks! again just let me know if you need better copies of any pages or if i still have managed to miss some out... always possible with me
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    what did ppl get for Phosphorus with soduim hydroxide
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    (Original post by alex7892)
    Grade boundary predictions? Lol why is everyone ignoring my comments x

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    A* 78
    A 69
    B 60
    C 52
    So slightly lower much than Jan 13
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    The grade boundaries won't change too much. I remember everyone thinking june 12 was horrific last year and they pretty much stayed the same (and tons of people complained to AQA.
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    ISNT 7a WRONG PPL
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    (Original post by alex7892)
    Grade boundary predictions? Lol why is everyone ignoring my comments x

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    Because nobody knows. And you can't really trust anyone who is not an Aqa examiner.

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    do you think for question 7 they will accept
    [fe(h20)6]2+ + 2NaOH --> Fe(h20)4(OH)2 + 2H20 + 2Na+
    etc.
    I think you were just supposed to put ionic oh-
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    (Original post by esl_94)
    Sorry for the delay - I think these are Questions 6 and 7 Attachment 228381Attachment 228382Attachment 228383Attachment 228384
    Again if I have missed any pages just let me know I seem to have 18 photos on my phone and have put 17 up here but I can't work out which I have missed!

    Cant you just put up the whole paper??
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    What's this question with substance Z (Co(NH3)2 cl2) ?? I don't remember it at all
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    (Original post by naeemkhan12)
    ISNT 7a WRONG PPL
    Yeahh the equation for Fe2+ is completely wrong
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    Isnt question 2(b) 26 kj mol???

    The enthalpy of hydration for the potassium ion is -322 and the dissociation for potassium bromide is +670, calculate the enthalpy of solution of potassium bromide:


    enthalpy of solution = lattice dissociation + sum of hydrations

    +26 = +670 + (-322 x 2)


    am I wrong??
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    (Original post by nimbusquaffle)
    2a) Cl- ion is a smaller ion than Br- so has greater electronegativity. water is polar so contains a ~+ H+ ion. therefore Cl-is more attracted to H2O than Br- so more energy is released when hydration happens
    b) 13kJmol-1
    c) increase in entropy and 1mole ---> 2moles. more disordered. ΔH<tΔS. therefore ΔG<0 nd feasible.
    d) have no idea!

    3a)i at 0K all substances are completely ordered. moles are constant with no vibrations. absolute entropy.
    ii as temperature increases entropy increases, molecules vibrate more violently becoming more disordered
    iii in line with L2
    iv phase change causes a sudden increase in entropy. boiling has a greater increase in entropy than melting so L2 is greater than L1.
    b)i ΔG=ΔH-TΔS can be rearranged to ΔG=-ΔST + ΔH. ΔS is m (gradient) ΔH is the constant c. ΔG is y and T is x. therefore follows the same equation. ΔS is negative due to negative gradient.
    ii as T increases TΔS, because ΔH is constant. as T increases ΔH - TΔS decreases, ΔG decreases.
    iii becomes feasible
    c)i -44.5 Jk-1mol-1
    ii 242 kJmol-1

    hopefully help, correction ma be needed!


    3 part 3, its unfeasible below 500K as G is positive.
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    (Original post by godjohnson)
    What's this question with substance Z (Co(NH3)2 cl2) ?? I don't remember it at all
    It was the one on the back of the paper, you had to calculate the mole ratio of chlorine to Cobalt (which was threene), deduce the structure [CoCl3(NH3)3] and then say why the mole ratio may eb different in practice (no clue).

    Guys do you think they would accept [CoCl3(NH3)] as in all fairness, knowing the coordination number of such a random complex is not on the spec?
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    (Original post by AspiringGenius)
    I found ti quite hard. I know I messed up the qmcDT equation and some of the cobalt chemistry equalling about 10 marks. Although if grade boundaries are low and I did well enough in Chem4 and the EMPA, An A* is achievable (I hope).

    you?
    I thought it was really quite hard too..the calculations were a lot more challenging than those on past papers I think. Especially the very last..I guessed the complex was CoNH34Cl2..lol. But I did get the ratio..I think I've lost all marks on the that delta T equation, I didn't use m I got the cobalt question though. I think I've lost at least 5 from earlier parts of the paper due to poor explanations..so I'm thinking at least 10-15, maybe more hopefully the GBs will be nice and low though..and I'm in the same position - CHEM4 and my ISA went really well, so hopefully this wont pull my UMS down massively. And I need an A*, not so sure what it will be in now though..
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    (Original post by alex7892)
    Grade boundary predictions? Lol why is everyone ignoring my comments x

    Posted from TSR Mobile
    I'm thinking in the range of 77-79 for an A*, 69-71 for an A etc, most probably on the lower side of those as there was a lot of maths that wasn't straightforward

    (Original post by godjohnson)
    What's this question with substance Z (Co(NH3)2 cl2) ?? I don't remember it at all
    Was on the back page..:eek:
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    (Original post by Croydon'Stepper)
    2a, you don't talk about electro negativity as it's not a covalent bond.

    2b I did the correct method, got -7kJmol-1, but I think I ****ed up the actually calculations

    Other than that, got the same as you!
    Which page is this unofficial mark scheme on?
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    (Original post by godjohnson)
    What's this question with substance Z (Co(NH3)2 cl2) ?? I don't remember it at all
    i did exactly the same
    i forgot to turn to the back page
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    (Original post by erniiee)
    Which page is this unofficial mark scheme on?
    Here's what someone posted as the unofficial mark scheme but it incomplete and there some errors.

    "This is nearly complete unofficial markscheme:

    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
    Its not
    [Fe(H2O)6]2+ + CO32- => FeCO3 + 3CO2 + 3H2O is wrong its:

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

    Can somebody finish this off"
 
 
 
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