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OCR Chemistry A Exam Thread (Breadth - May 27 2016 and Depth - June 10 2016) watch

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    (Original post by WhyAlwaysMe?!)
    Good idea.

    The boiling points of three liquids, A, B and C are 65, 141, and 80 respectively. Liquid A reacts with liquid B to produce liquid C and water. Distillation of the reaction mixture produces four pure liquids, which are collected as they form in separate beakers. Which beaker (1st, 2nd, 3rd or 4th) would contain water?


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    Is it 3?
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    (Original post by oni176)

    Electrophilic addition and nucleophilic substitution are the only mechanisms that involve curly arrows and any relevant dipoles.
    Is it better to draw the curly arrow from the OH- negative sign or from the lone pair?
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    (Original post by SaltandSugar)
    Is it better to draw the curly arrow from the OH- negative sign or from the lone pair?
    It doesn't matter.
    My teacher draws from the negative sign.
    But I prefer to draw from the lone pair - it makes more sense from the lone pair in my opinion
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    (Original post by harryleavey)
    It doesn't matter.
    My teacher draws from the negative sign.
    But I prefer to draw from the lone pair - it makes more sense from the lone pair in my opinion
    So does everything that has a negative sign have a lone pair then?

    So I can use either in all of the mechanisms?
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    (Original post by SaltandSugar)
    So does everything that has a negative sign have a lone pair then?

    So I can use either in all of the mechanisms?
    It's best to use lone pair as most mark schemes prefer this.
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    (Original post by SaltandSugar)
    So does everything that has a negative sign have a lone pair then?

    So I can use either in all of the mechanisms?
    Not everything with a negative sign has a lone pair, no.
    Nucleophiles must have an electron pair (as they are electron pair donors).
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    i was wondering since the specimen paper and practice paper where much harder than actual paper..what has everyone been getting in them for breadth?
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    Hi does anyone have the F321 and/or F322 (old spec) papers for June 2015 please


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    (Original post by fteam)
    i was wondering since the specimen paper and practice paper where much harder than actual paper..what has everyone been getting in them for breadth?
    How do you know they are harder than the actual paper?
    Are you comparing to the paper we haven't done yet?
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    Specimen paper are specifically produced to be harder and forces students to stretch their thoughts when applying chemistry, you can compare every specimen paper to actual papers they are much different and proof is the physics paper was actually easier than the specimen and practice paper, so i most definitely think they will do the same. Ocr is a business they try keep same number of percentage of students achieving A's B's etc as they don't want schools moving away from the exam board.
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    Alright I've got another multi choice question that I need help on please
    Which reactions is the enthalpy change equal to the bond enthalpy of H-Br?
    A) HBr ---> H + Br
    B) HBr ---> H+ + Br-
    C) HBr ---> 1/2 H2 + 1/2 Br2 (l)
    D) HBr ---> 1/2 H2 + 1/2Br2 (g)

    Thanks 😊
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    (Original post by Farmerjj)
    Alright I've got another multi choice question that I need help on please
    Which reactions is the enthalpy change equal to the bond enthalpy of H-Br?
    A) HBr ---> H + Br
    B) HBr ---> H+ + Br-
    C) HBr ---> 1/2 H2 + 1/2 Br2 (l)
    D) HBr ---> 1/2 H2 + 1/2Br2 (g)

    Thanks 😊
    Is it simply A, i think it's A


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    (Original post by Fish40)
    Is it simply A, i think it's A


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    Ok cheers man
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    (Original post by Farmerjj)
    Ok cheers man
    I might be wrong, I'm guessing, where did you get the question from?


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    (Original post by Fish40)
    I might be wrong, I'm guessing, where did you get the question from?


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    Just from my textbook, it's the OCR Oxford one
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    (Original post by SaltandSugar)
    These?
    Yesss thanks a lot!!


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    what mark out of 70 would i need for a C?
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    anyone?
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    It depends on how people do but I think 38/39 should be good for C based on previous grade boundaries
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    (Original post by Saaranjan)
    It depends on how people do but I think 38/39 should be good for C based on previous grade boundaries
    would u say 30-34 is a C
 
 
 
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