OCR Chemistry A 2016 unofficial mark scheme 27/05/16

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    (Original post by adamwall99)
    Yeah I want an answer to that too. I used the Relative Atomic Mass from the question before because the questions were c) i) and ii) so I presumed they were connected, can't remember what I got though but it was 3. something x10-22
    Maybe they did expect us to use the previously calculated value, either way it's a method mark, and they may allow either
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    (Original post by Bosssman)
    Thank you for your input, I'll add to the original
    can you put calculations in spoilers?
    (Original post by Bosssman)
    Maybe they did expect us to use the previously calculated value, either way it's a method mark, and they may allow either
    imo, if they wanted us to use a previous answer they would've said use a previous answer.
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    (Original post by alkaline.)
    can you put calculations in spoilers?
    Sorry I'm not sure how to do that as I'm a new member and I'm on my phone, not a computer, when I'm home I'll see what I can do
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    (Original post by Bosssman)
    Here's my attempt at an unofficial mark scheme, it is for the OCR Chemistry A, new spec, breadth in chemistry paper, really can only put the maths questions down, but if there are written ones I can remember I will put them down. This is only really for comparison of numbers, and general ideas

    Multiple choice:
    BCDACBBDCBCBBCBDDBBD (if anyone happened to store their multiple choice answers on their calculator, please post them below to compare)

    Same number of protons and electrons, different number of neutrons

    Relative atomic mass: 63.62
    No of atoms in 5.00g coin: 3.98 x 10^22 (3sf)
    Percentage error of water removed mass: 1.72%
    Volume of H2SO4 required to neutralise NaOH: 24.8cm^3
    Enthalpy change of reaction: -58.5 kJmol^-1
    Concentration of KI required: 3.3 moldm^-3
    Concentration in equilibrium question: 0.876 moldm^-3

    Homologous series: alkenes
    General formula: CnH2n



    Electron configuration of bromide ion: 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6

    Equilibrium question: The equilibrium position will shift to the right, as the forward reaction is exothermic, in an attempt to reduce the effect of the temperature decrease. The equilibrium position will also shift to the right as there are fewer gas molecules in the products of the forward reaction, in an attempt to reduce the effect of the pressure increase. This may vary to the actual conditions as low temperature reduces rate of reaction, and it's expensive to have a high pressure.

    Ways to reduce percentage uncertainty: use a larger mass of crystals to get larger mass of water removed, reducing % error

    To make sure mass of water removed is correct: reweigh and reheat, repeat until constant mass is achieved

    Halogen precipitate colours: chloride, white; bromide, cream; iodide, yellow

    Last question: step 1 reagent, Br2, step 2 reagent, NaOH

    If anyone remembers the written answers, please post and I'll add them,
    Any incorrect (although I don't think there are) please tell and I'll correct

    Also, post about how you found the exam, as this will give a good idication of grade boundaries
    Alkene to alkane: H2, nickel catalyst, 150 degrees CI put H3PO4 catalyst by mistake but put the other too things, how many marks was it do you rememberAlcohol --> H2SO4 + heat --> alkene^^what question was this
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    (Original post by medicapplicant)
    Alkene to alkane: H2, nickel catalyst, 150 degrees CI put H3PO4 catalyst by mistake but put the other too things, how many marks was it do you rememberAlcohol --> H2SO4 + heat --> alkene^^what question was this
    dw i didn't put 150degrees cause it doesn't even say temp in the textbook I swear.
    that question was right after the nickel catalyst question a diagram

    "BLANK - H2S04 catalyst and heat - THE GIVEN ALKENE - *line going downwards* ANOTHER BLANK"


    (Original post by Bosssman)
    Sorry I'm not sure how to do that as I'm a new member and I'm on my phone, not a computer, when I'm home I'll see what I can do
    kay babe
    [/SPOILER] at the end of what you want to put and
    [SPOILER] at the beginning of what you want to put

    or yh just wait til u get home

    I have a reequest: can you put number of marks after the questions pls?
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    (Original post by alkaline.)
    dw i didn't put 150degrees cause it doesn't even say temp in the textbook I swear.
    that question was right after the nickel catalyst question a diagram

    "BLANK - H2S04 catalyst and heat - THE GIVEN ALKENE - *line going downwards* ANOTHER BLANK"




    kay babe
    [/SPOILER] at the end of what you want to put and
    [SPOILER] at the beginning of what you want to put

    or yh just wait til u get home

    I have a reequest: can you put number of marks after the questions pls?
    I'll try and remember marks
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    (Original post by Bosssman)
    No, you had to put the x 10^22, and also I don't think significant figures was specified in the question
    It was, it said 3 significant figures


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    (Original post by Bosssman)
    Yes it was 24.8, that has been changed
    Do you remember what the question was for the 24.8
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    Anyone tell me how they got 58 or whatever it was for the enthalpy change, I got the 4... KJ then I think I divided it by like 0.174 to get 19?
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    (Original post by SGHD26716)
    Do you remember what the question was for the 24.8
    Calculate the minimum volume of H2SO4 needed to completely react with the NaOH
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    (Original post by connorhill)
    Anyone tell me how they got 58 or whatever it was for the enthalpy change, I got the 4... KJ then I think I divided it by like 0.174 to get 19?
    4.18*100 (mass of solution) * 10.5 (temperature increase) then divide by number of moles calculated, also for this question don't forget there is an independent mark for the negative sign!
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    For the last question is it correct for step 1 to add H2 to create the Alkene then for step 2 add OH- ions?
    Think the first step is wrong but would they credit step 2?
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    (Original post by HarryPrior16)
    For the last question is it correct for step 1 to add H2 to create the Alkene then for step 2 add OH- ions?
    Think the first step is wrong but would they credit step 2?
    Maybe, it's hard to tell how harsh the new spec mark scheme will be
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    Also for the water of crystallisation question was the answer (can't remember the first element so X) XCl3•6H2O
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    (Original post by HarryPrior16)
    Also for the water of crystallisation question was the answer (can't remember the first element so X) XCl3•6H2O
    It was Cr3Cl . 6H2O
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    (Original post by Bosssman)
    It was Cr3Cl . 6H2O
    *******s ahaha
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    (Original post by Bosssman)
    Calculate the minimum volume of H2SO4 needed to completely react with the NaOH
    I know this is unlikely that you remember this but do you know the equation and moles. I just can't remember the answer I wrote if it was right or not.
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    (Original post by SGHD26716)
    I know this is unlikely that you remember this but do you know the equation and moles. I just can't remember the answer I wrote if it was right or not.
    Sorry I can remember the equation but the critical information was the concentration of the solutions which I can't remember, sorry!
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    What do you think the grade boundaries could be? Last years old spec paper F321 was 77% for an A. That would be around 54 marks for an A.
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    (Original post by SGHD26716)
    What do you think the grade boundaries could be? Last years old spec paper F321 was 77% for an A. That would be around 54 marks for an A.
    I reckon around 80% for an A
 
 
 
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