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***2013 LC Chemistry Before/After***

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    #692
    Prodigious
    Closed Accounts Posts: 2,827 ✭✭✭Prodigious


    I got -350 for Kc?


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    #693
    Hamza Malik
    Registered Users Posts: 161 ✭✭Hamza Malik


    RML wrote: »
    For Q6, heat change, did anyone get -412.2?

    Yeah I was just staring the question when I saw 4 heat of formations.

    In the end I got -412 kj mol :P


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    #694
    Copper_pipe
    Registered Users Posts: 11,553 ✭✭✭✭Copper_pipe


    weirdspider wrote: »
    Around 138?

    ya I got that, thought I was wrong as it was very big :p


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    #695
    weirdspider
    Registered Users Posts: 346 ✭✭weirdspider


    For the radiation question did anyone get 1/8 for the last part?


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    #696
    weirdspider
    Registered Users Posts: 346 ✭✭weirdspider


    Prodigious wrote: »
    I got -350 for Kc?

    Kc is never negative though?


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    #697
    Laura229
    Registered Users Posts: 8 ✭Laura229


    What was the reason behing using water as the benzoic solvent?


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    #698
    RML
    Registered Users Posts: 439 ✭✭RML


    Yepp :)


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    #699
    Copper_pipe
    Registered Users Posts: 11,553 ✭✭✭✭Copper_pipe


    Ya I did .5 X .5 X .5 = 1/8


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    #700
    weirdspider
    Registered Users Posts: 346 ✭✭weirdspider


    Copper_pipe wrote: »
    ya I got that, thought I was wrong as it was very big :p

    Well if 2 people got the same then it must be right! Unless we are both wrong :P


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    #701
    Laura229
    Registered Users Posts: 8 ✭Laura229


    Laura229 wrote: »
    What was the reason behing using water as the benzoic solvent?

    As in why:)


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    #702
    ray2012
    Registered Users Posts: 893 ✭✭✭ray2012


    Jaysus I got 138 as well and I was sure I was wrong and thought of changing it..! Glad that other people got the same answer! :)


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    #703
    Copper_pipe
    Registered Users Posts: 11,553 ✭✭✭✭Copper_pipe


    weirdspider wrote: »
    Well if 2 people got the same then it must be right! Unless we are both wrong :P

    Us wrong??? NEVER!


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    #704
    ladymacbeth
    Registered Users Posts: 64 ✭✭ladymacbeth


    What about question 1 calculations, part (f)?
    I multiplied the answer by 5 as the water sample was titrated to 200cm3. Hope this was the right move lol


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    #705
    weirdspider
    Registered Users Posts: 346 ✭✭weirdspider


    Well I was crossing off the questions I got right as we were going along and the only ones I were unsure of the answers were the maths ones. And I'm now presuming they are correct since you guys got them answers too so now I am almost certainly in A1 territory :D


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    #706
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    Laura229 wrote: »
    What was the reason behing using water as the benzoic solvent?

    It is soluble at high temp (removes insoluble impurities such as Carbon) and it is insoluble at low temp (separates it from the soluble impurities)


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    #707
    RML
    Registered Users Posts: 439 ✭✭RML


    ladymacbeth wrote: »
    What about question 1 calculations, part (f)?
    I multiplied the answer by 5 as the water sample was titrated to 200cm3. Hope this was the right move lol

    Where is the 5 coming from?


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    #708
    ladymacbeth
    Registered Users Posts: 64 ✭✭ladymacbeth


    Laura229 wrote: »
    As in why:)
    Laura229 wrote: »
    What was the reason behing using water as the benzoic solvent?

    I said Cyclohexane. :confused:


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    #709
    weirdspider
    Registered Users Posts: 346 ✭✭weirdspider


    Right so
    Kc-138/139
    Fraction of mass left- 1/8
    Ppm O2-7.8(meaning the other calculations were correct)
    pH-11.18 or something?


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    #710
    Kingkumar
    Registered Users Posts: 59 ✭✭Kingkumar


    Laura229 wrote: »
    What was the reason behing using water as the benzoic solvent?

    i said because benzoic acid dissolves in hot water which is important so that we can do filitration and stuff.. and then it's not soluble in cold water so it crystallizes out. i explained it a bit more but thats basically it


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    #711
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    Wait guys, what was wrong with the apparatus in q2? I thought it was that one of the nozzles was the wrong way but I just saw a diagram that was an exact replicate of the one on the examination.
    Please don't tell me it was a lack of wire gauze/ tripod?


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    #712
    ladymacbeth
    Registered Users Posts: 64 ✭✭ladymacbeth


    Delighted when I saw Dissolved Oxygen question as Question 1! But it was tricky enough :P The paper was good but the questions themselves were actually quite tricky


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    #713
    Kingkumar
    Registered Users Posts: 59 ✭✭Kingkumar


    Deleted User wrote: »
    Wait guys, what was wrong with the apparatus in q2? I thought it was that one of the nozzles was the wrong way but I just saw a diagram that was an exact replicate of the one on the examination.
    Please don't tell me it was a lack of wire gauze/ tripod?

    the safety tube wasnt pushed into the water..


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    #714
    xJEx
    Registered Users Posts: 166 ✭✭xJEx


    what were the differences between chem and nuclear reactions?


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    #715
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    weirdspider wrote: »
    Right so
    Kc-138/139
    Fraction of mass left- 1/8
    Ppm O2-7.8(meaning the other calculations were correct)
    pH-11.18 or something?

    All match my answers :)
    And for q6, it was a negative in the hundreds is all I remember.


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    #716
    weirdspider
    Registered Users Posts: 346 ✭✭weirdspider


    Deleted User wrote: »
    Wait guys, what was wrong with the apparatus in q2? I thought it was that one of the nozzles was the wrong way but I just saw a diagram that was an exact replicate of the one on the examination.
    Please don't tell me it was a lack of wire gauze/ tripod?

    I said no steam trap and to remove the heat source to rectify it :/ was unsure of that one!


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    #717
    ladymacbeth
    Registered Users Posts: 64 ✭✭ladymacbeth


    Deleted User wrote: »
    Wait guys, what was wrong with the apparatus in q2? I thought it was that one of the nozzles was the wrong way but I just saw a diagram that was an exact replicate of the one on the examination.
    Please don't tell me it was a lack of wire gauze/ tripod?

    I said the Liebeg Condenser was assembled incorrectly. They never include wire gauze etc in their diagrams anyways


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    #718
    RML
    Registered Users Posts: 439 ✭✭RML


    xJEx wrote: »
    what were the differences between chem and nuclear reactions?

    I talked about the toxic waste produced by nuclear reactions and the expense..


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    #719
    weirdspider
    Registered Users Posts: 346 ✭✭weirdspider


    I'd say about 10% of candidates attempted 2 and 6


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    #720
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    Kingkumar wrote: »
    the safety tube wasnt pushed into the water..

    Damn! In all the diagrams I've ever seen, one nozzle of the liebig condenser points down and one points up. I thought that was the wrong set up.


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    #721
    Prodigious
    Closed Accounts Posts: 2,827 ✭✭✭Prodigious


    RML wrote: »
    I talked about the toxic waste produced by nuclear reactions and the expense..

    chemical reactions do not affect the nucleus


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