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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 Pataiiii)
    It's because the product of the dehydration reaction is methylpropene, so it must be a branched halogenoalkane.
    Thanks!
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    Wow, the January 2013 paper was ridiculously generous. If only I resat it in January .
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    (Original post by Dejir)
    How is it possible to get 80 out of 100 I just keep getting 70 even marking generously


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    what kinds of things are you getting wrong? you've probably just not understood certain topics so revise them now and go back and see if you can do the questions later.
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    (Original post by needtosucceed=))
    the enthalpy change that occurs when one mole of a compound is formed from its constituent elements in their standard states under standard conditions of 298k and 1atm.

    negged?! seriously..
    Yeah I'm a new member and I don't get why people are negatively rating my explanations to people!
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    (Original post by JimmyA*)
    Wow, the January 2013 paper was ridiculously generous. If only I resat it in January .
    same I wish i did now but I resat f321 in january and I had f324, didn't really wanna have 3 chemistry exams lol.
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    (Original post by Anonymous1717)
    Yeah I'm a new member and I don't get why people are negatively rating my explanations to people!
    jealousy :rolleyes:
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    (Original post by pataiiii)
    it's because the product of the dehydration reaction is methylpropene, so it must be a branched halogenoalkane.
    pataiiii is so fat that he sat on crude oil and it cracked...
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    (Original post by Dejir)
    How is it possible to get 80 out of 100 I just keep getting 70 even marking generously


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    What are your usual mistakes in? Long questions, short one markers or the maths part?
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    What mark out of 100 do you think you need to get 150 UMS ?


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    (Original post by needtosucceed=))
    1) the chlorine can go on any of the carbon atoms as its an unsymmetrical molecule so any carbon it goes on will give a different isomer. theres 8 carbons so 8 isomers

    2) you see the hydrogen atoms on ethane, in radical substitution more than 1 of the hydrogens can get substituted with a bromine atom. so bromoethane could form, 1,2-dibromoethane, 1,1,2-tribromoethane etc. also in the termination step different free radicals can combine to make different molecules eg. h + br = hbr, br + br = br2 etc

    3) this depends on the reaction really, whether the forward is exothermic or endothermic
    main points are
    - high temperate and/or pressure to give a fast rate of reaction
    - but if the forward reaction is exothermic you want a high enough temperature for a fast rate of reaction without compromising yield/shifting the position of equilibrium to the left
    - if theres more moles of gas on the right hand side you want a high enough pressure to give a fast rate of reaction without compromising yield/shifting equilibrium to the left
    Ah okay thank you.
    Just one question. for the first question, why don't you start making branches? Like adding methyl groups and stuff?
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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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    something around 90 most likely
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    (Original post by needtosucceed=))
    OP
    ???????????
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    (Original post by 566)
    Ah okay thank you.
    Just one question. for the first question, why don't you start making branches? Like adding methyl groups and stuff?
    you do/can. if you drew them all out and did that and put the chlorines on all the different carbons etc some would get repeated. you'd be left with 8 unique ones.
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    (Original post by ii-mohsin-ii)
    ???????????
    opening post, 1st post of this thread
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    (Original post by needtosucceed=))
    you do/can. if you drew them all out and did that and put the chlorines on all the different carbons etc some would get repeated. you'd be left with 8 unique ones.
    Ah okay, so if i come upon this kind of question in an exam, do you think I should draw it out and see, because that takes a lot of time, or is the answer always going to be the number of carbon atoms there are?
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    a branched chain is one with alkyl groups right?
    And is ''main hydrocarbon chain'' another way of saying the chain where there's the most carbon atoms?
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    (Original post by 566)
    Ah okay, so if i come upon this kind of question in an exam, do you think I should draw it out and see, because that takes a lot of time, or is the answer always going to be the number of carbon atoms there are?
    best to just count the number of carbons (as long as the compounds unsymmetrical)
    its only gonna be worth 1 mark so no point spending ages on it. but if you've got time left at the end you might as well
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    (Original post by cookiess)
    a branched chain is one with alkyl groups right?
    And is ''main hydrocarbon chain'' another way of saying the chain where there's the most carbon atoms?
    yep branched
    and yep the longest carbon chain
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    (Original post by needtosucceed=))
    best to just count the number of carbons (as long as the compounds unsymmetrical)
    its only gonna be worth 1 mark so no point spending ages on it. but if you've got time left at the end you might as well
    Ok thank you so much!!!
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    Anyone got the jan 2013 paper?
 
 
 
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