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OCR A Chemistry F322 Chains, Energy and Resources Thu 19 Jan 2012 watch

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    (Original post by faz_341)
    what was the emperical formula for a cycloalkane with 6 carbons then? is it not Ch2
    it is
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    (Original post by Eternal Rest)
    Also, what did people get for the CFCs being hydrolysed question?

    I put it doesn't have hydrogen so it can't make hydrogen bonding, is that right?
    Yepppppp!
    No O-H bonds so can't form H bonds with H20 molecules!
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    (Original post by Tyles)
    it is
    Woo!
    did anyone get 431.5 for bond enathlp of hcl?
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    (Original post by Conal09)
    What did anyone get for the Sulfuric acid percentage yield question?? I got 94% but really had no idea...
    Yuuppp! Got the same.
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    (Original post by maryam.asmari)
    Yepppppp!
    No O-H bonds so can't form H bonds with H20 molecules!
    i put no oh group in molecule so cant bond hydrogen bond with water dyu think id get the mark?
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    (Original post by faz_341)
    Woo!
    did anyone get 431.5 for bond enathlp of hcl?
    I got +584, but I'm probably wrong lol.

    Can you tell me how you worked it out please?
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    (Original post by Eternal Rest)
    Oh yeah, what did people get for the empirical formula question?
    I got C6H12 but wasn't too sure. :/
    Doesn't empirical formula mean simplest? I put CH2
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    The sulfuric % yield IS 94% but im sure they will accept 93%
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    (Original post by maryam.asmari)
    Doesn't empirical formula mean simplest? I put CH2
    I put CH2 at first but I thought it's impossible for one carbon atom to be cyclic.
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    (Original post by faz_341)
    i put no oh group in molecule so cant bond hydrogen bond with water dyu think id get the mark?
    I think you should do! Unless they penalize you on 'Hydrogen bonding'. Don't think they would do. But it came up on a past paper and it did say H bonding, because that's the whole point of the OH to bind with H in H20 . Hopefully they don't penalize you though.
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    (Original post by Eternal Rest)
    I got +584, but I'm probably wrong lol.

    Can you tell me how you worked it out please?
    679 + ? = -184
    so ? equals 862
    since there is 2hcl divide by two = 431.5
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    (Original post by faz_341)
    Woo!
    did anyone get 431.5 for bond enathlp of hcl?
    correct.

    Always work backwards to check your result..

    431.5 x 2 = 863
    863 - 184 = 679

    679 was the total of the reactants.
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    (Original post by Eternal Rest)
    I put CH2 at first but I thought it's impossible for one carbon atom to be cyclic.
    I'm don't know anymore. I'm pretty sure it is CH2. They DIDN'T* say 'make sure the empirical formula is also cyclical'. It's just the simplest whole number ratio.?
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    (Original post by Tyles)
    correct.

    Always work backwards to check your result..

    431.5 x 2 = 863
    863 - 184 = 679

    679 was the total of the reactants.
    did you get -134 kjmol-1 for the answer on the mg thing one?
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    empiracal is simplest whole number ratio so its CH2
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    (Original post by faz_341)
    679 + ? = -184
    so ? equals 862
    since there is 2hcl divide by two = 431.5
    I added Cl2 and H2, then took 184 from the total.

    Then I divided the answer by 2, and got +584.

    I've probably got it wrong lol.
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    (Original post by otrivine)
    did you get -134 kjmol-1 for the answer on the mg thing one?
    yes i did -2.68/0.02 i think
    what i founbd weird fore this was it said answer must be in 3 sig fig and answer was already in 3sigfig
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    (Original post by faz_341)
    yes i did -2.68/0.02 i think
    what i founbd weird fore this was it said answer must be in 3 sig fig and answer was already in 3sigfig
    exacly hahaha and did you get for part a ) 2.6753 something cause i did the 50+0.05 ? and for the question on suggest why cfc banned but still there are i wrote of planes release cfcs and cars when release exhaust fume contains cfc?
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    can you say for the bit about why cfcs dont hydrolise with water, because of the polarity of the c-f and c-cl bonds, repel the OH?!?!?!
    and for the energy question where you had to work out the Q = MxcxdeltaT, and then work out the number of moles(which was 0.02).. and then the next question you had to divide Kj/moles..did you times your answer by two? because in the jan 2011 paper, it was a similar question and you had to times by 2
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    I got CH2. I thought this was a well balanced paper compared to previous ones. No 10 markers!
 
 
 

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