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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 Hardworker?)
    Some help please,
    do we need to know specific polymers and their uses, if so which ones?
    Just Choloroethne to make PVC
    AND
    Tetrafluoroethene to make PTFE
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    (Original post by TheFootyKing19)
    Ooooops yeah! Mis read functional group somewhere!

    Define Hess's Law
    Hess's Law states that if a reaction can take place by more than one route and the initial and final conditions are the same, the total enthalpy change is the same for each route.
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    (Original post by Hardworker?)
    Some help please,
    do we need to know specific polymers and their uses, if so which ones?
    Not necessarily, I am sure...
    They'll be put in light context - Chemistry normally is examined very specific to the specification...
    That's awesome for us!



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    (Original post by F95)
    ohh okay thankyou!! is that the case for all questions like this? or just for this particular q?
    All questions like this, although they're usually nice and give whole numbers, but decimals do trip people up so watch out
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    (Original post by Chemistry95)
    I'm doing this as a resit, and im just saying if anybody does do badly once you do A2 then you come back to this it's so much easier so if you do bad this year just resit it next june and you'll most likely do so much better
    Why is A2 harder? What is harder about it? I'm debating about whether to drop chemistry or not. I don't need it for uni as I wanna do maths.
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    (Original post by needtosucceed=))
    I hope that makes sense

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    (Original post by elliebennett)
    Hey,
    basically you have to kind of form an algebraic equation.

    So you know the overall enthalpy change = -184
    and you H-H bond = 463
    and Cl-Cl bond = 246
    but you wanna find out 2HCl
    soo.. H-H + Cl-Cl --> 2HCl = -184

    463 + 246 --> 2HCl = -184
    463 + 246 = 679,
    so you have work out what you would have take from 679 to make the overall enthalpy change = -184, (basically work out the difference)
    so 679 - 863 = -184, so you know that 2HCl must = 863

    however the question asks for just HCl, so you just divide 2HCl = 863/2 = 431.5!
    Thank you guys soooo much!!!
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    (Original post by iamvick)
    Hess's Law states that if a reaction can take place by more than one route and the initial and final conditions are the same, the total enthalpy change is the same for each route.
    Top!

    State environmental concerns over:
    HCl (1)
    CO (2)
    NO (2)

    State the uses of methanol (2)
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    (Original post by GeneralOJB)
    Why is A2 harder? What is harder about it? I'm debating about whether to drop chemistry or not. I don't need it for uni as I wanna do maths.
    a2 is a progression from AS, therefore naturally its harder..the concepts arent as straight forward as they are at AS and the exams can trip you up. its interesting though
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    Also about question 5 b on jan 2012 is there a typo?? or just me?
    • Thread Starter
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    (Original post by TheFootyKing19)
    Top!

    State environmental concerns over:
    HCl (1)
    CO (2)
    NO (2)

    State the uses of methanol (2)
    Can produce acid rain, or react with buildings
    Is toxic and reduces the amount of oxygen going in your body
    Low level ozone, photochemical smog

    Petrol additive
    For Feedstock




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    (Original post by TheFootyKing19)
    Top!

    State environmental concerns over:
    HCl (1)
    CO (2)
    NO (2)

    State the uses of methanol (2)
    sorry im just gonna butt in..

    - corrosive and toxic
    - toxic, reduces the ability of the blood to carry oxygen
    - forms photochemical smog and low level ozone
    - petrol additive, making esters, methylated spirits (i think?)


    define average bond enthalpy (2)
    why would the value for enthalpy change be different when using average bond enthalpy 1)
    why is international cooperation important (3)
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    what are the definitions guaranteed to get maximum marks for:
    Enthalpy change of reaction/ formation and combustion?
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    If anyone can be bothered, try these:

    Define average bond Enthalpy (2)
    Define standard Enthalpy change of reaction (2)
    State standard conditions (1)
    State the test and colour change for Alkane and Alkene (3)
    How can you make Butylpentanoate, state the conditions and give an equation (5)
    How does an increase in concentration increase the rate of reaction? (2)
    State two features of E/Z isomerism? (2)
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    (Original post by SAS18)
    Also about question 5 b on jan 2012 is there a typo?? or just me?
    what word? seems fine to me
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    (Original post by TheFootyKing19)
    If anyone can be bothered, try these:

    Define average bond Enthalpy (2)
    Define standard Enthalpy change of reaction (2)
    State standard conditions (1)
    State the test and colour change for Alkane and Alkene (3)
    How can you make Butylpentanoate, state the conditions and give an equation (5)
    How does an increase in concentration increase the rate of reaction? (2)
    State two features of E/Z isomerism? (2)
    the average enthalpy change when one mole of gaseous covalent bonds are broken
    the enthalpy change that occurs in the molar quantities expressed in a chemical equation under standard conditions
    298k and 1atm
    alkene - br2 would decolourise it, alkane - it would stay brown
    butan-1-ol + pentanoic acid. conc h2so4 + reflux. cba to write the equation lol
    more particles per unit volume therefore more successful/frequent collisions
    c=c, restricted rotation and each carbon bonded to 2 different atoms/groups of atoms
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    (Original post by needtosucceed=))
    what word? seems fine to me
    could you tell me how to do it please?
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    (Original post by SAS18)
    could you tell me how to do it please?
    use the equation actual/theoretical x100

    ignore the tonnes, just use grams

    work out the moles of each one then divide one by the other.
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    (Original post by GeneralOJB)
    Why is A2 harder? What is harder about it? I'm debating about whether to drop chemistry or not. I don't need it for uni as I wanna do maths.
    To be honest if your good at maths you'll find it easy as most people struggle with Unit 5 as it's lots of calculations. It is harder but alot more interesting. If you dropped chemistry what would your subjects be?
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    What is the best way to revise module 4?


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