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AQA A-level Chemistry paper 2 7405/2 Unofficial Markscheme Watch

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    (Original post by Sapereaude45)
    Yeah, looks good to me.I still don't understand how people got 145mg.I think they may have forgot to subtract the two volumes of gas to find CO2, unless it was a silly error on my part!
    After calculating v in m3 for Co2 then I and others divided by 6 to get m3 or v of the initial reactant P. Then used this to get 145
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    (Original post by Hassankhan2405)
    Did anyone get 870Mg for one of the questions? The Ideal Gas Equation?
    I did but i got so confused no clue if that's right
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    (Original post by emilyvrl)
    Step 1 :
    H2SO4 + HNO3 --> H2NO3 + HSO4

    Step 2 :
    Methylbenzene + HNO3 --> methylnitrobenzene + H2O ( conc H2SO4 catalyst )

    Step 3 :
    MethylNitrobenzene + 6[H] --> methylphenylamime + 2H2O ( Sn/HCl catalysts , room température )

    Okay so that's all I did for the very last question . It makes sense to me but I have no clue if it's right . Any opinions ?

    I done :
    Step 1:
    Free radical sub with chlorine radicals so the methyl group on benzene becomes ch2cl

    Step 2:
    Nucleophillic sub with CN so the Cl is substituted with CN to form a nitrile (because the carbon chain needs to be longer)

    Step 3:
    Reduce the nitrile using LiAlH4 in Ether
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    (Original post by Sapereaude45)
    Yeah, looks good to me.I still don't understand how people got 145mg.I think they may have forgot to subtract the two volumes of gas to find CO2, unless it was a silly error on my part!
    I got 149 mg as I used the value for 155 volume then divided by 5 as the only volume left then did that times 114 (mr of p) then x1000 from g to mg
    Pretty sure that is my error.
    Most people done:
    (105000x335x10^-6)/(8.31x298)
    N=1.42x10^-2
    Then divide by 11 (total number of moles of gaseous products)
    Mass = NxMr
    Mass = 1.29x10^-2 x 114
    Mass= 1.47x10^-1 grams x1000
    Mass = 147mg (3sf)
    I feel like that's right but then again I haven't used the volume of 155 x10^-6 however the various methods that I've used to work it out has given the answer roughly around 147 mg but it could as well be something else
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    (Original post by emilyvrl)
    Step 1 :
    H2SO4 + HNO3 --> H2NO3 + HSO4

    Step 2 :
    Methylbenzene + HNO3 --> methylnitrobenzene + H2O ( conc H2SO4 catalyst )

    Step 3 :
    MethylNitrobenzene + 6[H] --> methylphenylamime + 2H2O ( Sn/HCl catalysts , room température )

    Okay so that's all I did for the very last question . It makes sense to me but I have no clue if it's right . Any opinions ?
    did the exact same thing but its wrong i didnt read the damn question such an easy 5 marks
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    (Original post by tangled23)
    did the exact same thing but its wrong i didnt read the damn question such an easy 5 marks
    If you had seen the structure properly it had no methyl group at the end so something must-have been tested with methyl group hence do cl2 or br2 in if light to get ch2cl which can be reached with KCN and then reduced to amine
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    (Original post by Balthznar)
    I got 149 mg as I used the value for 155 volume then divided by 5 as the only volume left then did that times 114 (mr of p) then x1000 from g to mg
    Pretty sure that is my error.
    Most people done:
    (105000x335x10^-6)/(8.31x298)
    N=1.42x10^-2
    Then divide by 11 (total number of moles of gaseous products)
    Mass = NxMr
    Mass = 1.29x10^-2 x 114
    Mass= 1.47x10^-1 grams x1000
    Mass = 147mg (3sf)
    I feel like that's right but then again I haven't used the volume of 155 x10^-6 however the various methods that I've used to work it out has given the answer roughly around 147 mg but it could as well be something else
    It does make sense but why would you subtract the volumes?The volume lost was the CO2 removed after combustion.I probably being an idiot though.
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    Was the last question anything to do with nitrobenzene?
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    (Original post by Emz99)
    fam you is smart. What unis did you apply too?
    Loool nah man I'm just about surviving the year

    And Birmingham, Newcastle, Leeds, UCL and Manchester lol
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    (Original post by Sapereaude45)
    It does make sense but why would you subtract the volumes?The volume lost was the CO2 removed after combustion.I probably being an idiot though.
    Tbh I don't know why it gave us both volumes as I believe we only hat to use one of them, whether you used the 335 and divided by 11 or used 155 and divided by 5 should theoretically give you the same values but ofcouse they didn't. But like you say I have no idea why you would minus the volumes as that will give you the volume left at which 5H2O was moles of product left.

    335-155=180cm^3
    Use the same method with this new volume and divide by 6 moles
    You get 145mg of P
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    How many marks would I get for getting 15.8 for Ea instead of 50.7 as I thought A was given not lnA. I'm assuming I get 2/4.
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    (Original post by Balthznar)
    Tbh I don't know why it gave us both volumes as I believe we only hat to use one of them, whether you used the 335 and divided by 11 or used 155 and divided by 5 should theoretically give you the same values but ofcouse they didn't. But like you say I have no idea why you would minus the volumes as that will give you the volume left at which 5H2O was moles of product left.

    335-155=180cm^3
    Use the same method with this new volume and divide by 6 moles
    You get 145mg of P
    I did use 180cm^3.I must have made a substitution error.Ah, well maybe 2 marks lost? At least it's all clearcup now
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    (Original post by NiceB8M8)
    How many marks would I get for getting 15.8 for Ea instead of 50.7 as I thought A was given not lnA. I'm assuming I get 2/4.
    Yeah about 2-one for that silly error an one for writing down the incorrect value, assuming your rearanging was correct of course.
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    Btw guys just wondering are the grades based on raw scores only for the new a level or still ums?
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    (Original post by 1anonomous)
    Btw guys just wondering are the grades based on raw scores only for the new a level or still ums?
    Raw grades I believe except for Maths and Further Maths
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    (Original post by brumtown0121)
    Loool nah man I'm just about surviving the year

    And Birmingham, Newcastle, Leeds, UCL and Manchester lol
    What course did you apply to? medicine?
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    (Original post by Sapereaude45)
    Raw grades I believe except for Maths and Further Maths
    Thanks- so what do u think grade boundaries will be like for this paper?
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    (Original post by Hazzab911)
    Yes I did - not sure if its correct though
    Unfortunately the correct answer was 148 mg.did you use that total 330cm3 gas volume.
    They reacted the gas with excess NaOH and i believe it was something like 180cm3 left after that.
    So u needed to do 330 Minus that value left after reaction to work out the volume of CO2.
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    For the 1,3 dinitrobenzene where it asked you for electrophilic substitution, does anyone remember the exact question? Did they ask you to form 1/3 dinitrobenzene from benzene or 1-nitrobenzene?
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    (Original post by 1anonomous)
    Thanks- so what do u think grade boundaries will be like for this paper?
    I think this one was a tiny bit harder than paper one because of all that chromatography and NMR stuff.
    Maybe around:
    75%A*
    65%A
    55%B
    45%C
    What do others think?
 
 
 
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