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OCR Chemistry F322~ 4th June 2013~ AS Chemistry watch

  • View Poll Results: How did you find the exam
    Hard A= 72
    42
    15.22%
    It was okay A= 76
    99
    35.87%
    Easy A= 79
    75
    27.17%
    Very Easy A=82
    60
    21.74%

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    (Original post by kingmango)
    Anyone got the jan 2013 paper?
    opening post.
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    Could they ask about preparing an ester? Page 155 on OCR endorsed book
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    (Original post by Saif95)
    Could they ask about preparing an ester? Page 155 on OCR endorsed book
    all they'd ask is how to make one. so acid + alcohol and conditions of reflux and an acid catalyst.
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    guys anyone know the june 2009 grade boundaries?
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    (Original post by Kitnimohabbathai)
    guys anyone know the june 2009 grade boundaries?
    its at the end of the mark scheme for that paper
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    (Original post by Anonymous1717)
    Thanks!
    No problem.
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    Predictions anyone? 😊


    Posted from TSR Mobile
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    I don't know if this is really obvious but when you do the Q=mcat equation how do you know if you get it in j or kj? also, can it ever be negative?
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    Help needed!
    H(2) + Cl(2) --> Cl(2) enthalpy change= -418 kJ mol^(-1)

    bond enthalpy for H-H is +436 and for Cl-Cl is +243

    work out the bond enthalpy for H-Cl?
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    (Original post by chasdfghjk)
    I don't know if this is really obvious but when you do the Q=mcat equation how do you know if you get it in j or kj? also, can it ever be negative?
    It is in joules as the units of the heat capacity of water is in J g-1 K-1. It will not be negative, you need to decide if it is negative or not based on whether the temperatuere increases or decreases.
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    (Original post by chasdfghjk)
    I don't know if this is really obvious but when you do the Q=mcat equation how do you know if you get it in j or kj? also, can it ever be negative?
    the units for q are joules, therefore your answer will automatically be in joules. they always ask for it in kj so divide your answer by 1000.
    you cant have a negative energy, you can only have negative enthalpy changes, theyre different things so only give a negative sign when it asks for an enthalpy change (only if the temperatures gone up though)
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    (Original post by chasdfghjk)
    I don't know if this is really obvious but when you do the Q=mcat equation how do you know if you get it in j or kj? also, can it ever be negative?
    no it will never be negative for the q=mcat because you can't have a negative mass value and when you divide the q=mcat by 1000 you always get it in KJ when you dont divide it by 1000 you will always get in J

    Hope this helped
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    (Original post by ChestnutHero)
    What mark out of 100 do you think you need to get 150 UMS ?


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    94/100 usually

    https://www.whatdotheyknow.com/reque...ogy_a?unfold=1


    may get higher as students are more prepared apparently due to more past papers available..
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    (Original post by rosie66)
    Help needed!
    H(2) + Cl(2) --> Cl(2) enthalpy change= -418 kJ mol^(-1)

    bond enthalpy for H-H is +436 and for Cl-Cl is +243

    work out the bond enthalpy for H-Cl?

    ? The enthalpy change for H2 + CL2 -> CL2 is 0 kJ mol-1
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    (Original post by rosie66)
    Help needed!
    H(2) + Cl(2) --> Cl(2) enthalpy change= -418 kJ mol^(-1)

    bond enthalpy for H-H is +436 and for Cl-Cl is +243

    work out the bond enthalpy for H-Cl?

    are you sure you copied the equation down write?
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    how many UMS would you get with 95 raw mars?
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    (Original post by tanja55)
    are you sure you copied the equation down write?
    yeah sorry.... H(2) + Cl(2) --> 2HCl

    sorry
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    (Original post by tanja55)
    how many UMS would you get with 95 raw mars?
    100 usually
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    (Original post by tanja55)
    are you sure you copied the equation down write?
    your english is killing me
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    Doing q2 ii of june 11 paper

    I said heat under reflux as the reaction conditions, but mark scheme says:

    distil --> Guidance: Reflux CONs distil mark

    what does the CON mean?
 
 
 
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