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

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    #752
    Laura229
    Registered Users Posts: 8 ✭Laura229


    Surely that alone wasnt worth 9 marks though?


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    #753
    lizardspock
    Registered Users Posts: 46 ✭lizardspock


    There was a pretty bad reaction to the paper from my class, although I thought it was fair enough to be honest. Really hoping I've done enough to secure the A1... Did 10 questions but just kinda found there was a part to most questions which could have the potential to be a bit vague in the marking scheme or parts with just a general sting in them! :/ fingers crossed!


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    #754
    comeclosa
    Registered Users Posts: 112 ✭✭comeclosa


    Corrosive for the hazard, yes? :P


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    #755
    SecondMan
    Registered Users Posts: 236 ✭✭SecondMan


    comeclosa wrote: »
    Corrosive for the hazard, yes? :P

    Yes. I drew a hand that resembled a side-view of a rabbit's head.


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    #756
    Hamza Malik
    Registered Users Posts: 161 ✭✭Hamza Malik


    comeclosa wrote: »
    Corrosive for the hazard, yes? :P

    Yeah I drew the picture of the test tube leaking on to a hand with a dead fish in the background :D


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    #757
    ladymacbeth
    Registered Users Posts: 64 ✭✭ladymacbeth


    IMG_0671.JPG

    Already hitting me that I was wrong. :(


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    #758
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    ladymacbeth wrote: »
    IMG_0671.JPG

    Already hitting me that I was wrong. :(

    Is n1 not = 2 and n2 = 1??


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    #759
    _LilyRose_
    Registered Users Posts: 211 ✭✭_LilyRose_


    ladymacbeth wrote: »
    IMG_0671.JPG

    Already hitting me that I was wrong. :(

    But isn't the ratio of the iodine to thiosulfate 1:4?


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    #760
    ladymacbeth
    Registered Users Posts: 64 ✭✭ladymacbeth


    Deleted User wrote: »
    Is n1 not = 2 and n2 = 1??

    :eek:

    FUUUUUU*****

    Ok. Lesson learned. This is what happens when everything depends on this subject and you're stress levels are at an all time high. This is what happens when you don't read a question properly.

    I will remain calm and not shred my exam paper into pieces in frustration. :mad:


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    #761
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    _LilyRose_ wrote: »
    But isn't the ratio of the iodine to thiosulfate 1:4?

    Nope.
    Iodine to Thiosulfate
    1 : 2

    Oxygen to Iodine
    1 : 2

    Therefore
    Oxygen to Thiosulfate
    1 : 4


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    #762
    _LilyRose_
    Registered Users Posts: 211 ✭✭_LilyRose_


    Deleted User wrote: »
    Nope.
    Iodine to Thiosulfate
    1 : 2

    Oxygen to Iodine
    1 : 2

    Therefore
    Oxygen to Thiosulfate
    1 : 4

    Ah yes.








    F************


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    #763
    Laura229
    Registered Users Posts: 8 ✭Laura229


    For the ammonia reaction was it wrong to say high pressure and low temperature?


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    #764
    ladymacbeth
    Registered Users Posts: 64 ✭✭ladymacbeth


    _LilyRose_ wrote: »
    Ah yes.








    F************




    hahahaha i'm not alone.
    I'm literally so angry I'm laughing it off.
    hahahaha... wtf???!!


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    #765
    _LilyRose_
    Registered Users Posts: 211 ✭✭_LilyRose_


    ladymacbeth wrote: »
    hahahaha i'm not alone.
    I'm literally so angry I'm laughing it off.
    hahahaha... wtf???!!

    When I looked at my book like two minutes before the exam I had 1:4 highlighted for the winkler calculations I'm soooooo annoyed at myself now lololololol!


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    #766
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    Laura229 wrote: »
    For the ammonia reaction was it wrong to say high pressure and low temperature?

    Which question was this?


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    #767
    xJEx
    Registered Users Posts: 166 ✭✭xJEx


    Laura229 wrote: »
    For the ammonia reaction was it wrong to say high pressure and low temperature?

    I was gonna do that but then I figured it wasnt that since it was a rates not equil. Q ... pus a low temperature increases yield of ammonia but actualy slows down the rate :/

    i said increased concentrations and temperature


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    #768
    xJEx
    Registered Users Posts: 166 ✭✭xJEx


    What answers did people get for Q3? I got .075 moles, then 4.347 for heat change and 57.96 for heat of reaction


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    #769
    ladymacbeth
    Registered Users Posts: 64 ✭✭ladymacbeth


    _LilyRose_ wrote: »
    When I looked at my book like two minutes before the exam I had 1:4 highlighted for the winkler calculations I'm soooooo annoyed at myself now lololololol!

    So should it have been 1:4?
    Or 2:1 as was suggested in the equation?


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    #770
    _LilyRose_
    Registered Users Posts: 211 ✭✭_LilyRose_


    ladymacbeth wrote: »
    So should it have been 1:4?
    Or 2:1 as was suggested in the equation?

    I honestly have no idea! Most people here and that I talked to got different to me but I suppose we'll have to wait to view the papers if we have to haha!


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    #771
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    ladymacbeth wrote: »
    So should it have been 1:4?
    Or 2:1 as was suggested in the equation?

    I worked with 2:1 for the calculation as we needed the concentration of iodine for the question

    Then it asked to work with O2 so I halved the molarity of the iodine. (as 2 moles are liberated for every 1 mole O2)
    And then used this figure for the rest of the calculations :)


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    #772
    Glee_GG
    Registered Users Posts: 522 ✭✭✭Glee_GG


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

    Gas I said "the flask appear to be hovering mid-air so you should put a tripod and gauze underneath" :L Its still true though even if I know they would have used it, they didn't put it in the picture!


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    #773
    SecondMan
    Registered Users Posts: 236 ✭✭SecondMan


    xJEx wrote: »
    I was gonna do that but then I figured it wasnt that since it was a rates not equil. Q ... pus a low temperature increases yield of ammonia but actualy slows down the rate :/

    i said increased concentrations and temperature

    Increased pressure would work too as it would cause an increase in collisions.


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    #774
    Kingkumar
    Registered Users Posts: 59 ✭✭Kingkumar


    Glee_GG wrote: »
    Gas I said "the flask appear to be hovering mid-air so you should put a tripod and gauze underneath" :L Its still true though even if I know they would have used it, they didn't put it in the picture!

    hahaha i was going to put that as well :D


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    #775
    xJEx
    Registered Users Posts: 166 ✭✭xJEx


    SecondMan wrote: »
    Increased pressure would work too as it would cause an increase in collisions.

    Yeah but low temperature wouldn't. It's kind of a messed up question cause temperature would speed it up but it would decrease the yield of ammonia and theyre asking how to speed up the reaction of ''the production of ammonia''


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    #776
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    xJEx wrote: »
    Yeah but low temperature wouldn't. It's kind of a messed up question cause temperature would speed it up but it would decrease the yield of ammonia and theyre asking how to speed up the reaction of ''the production of ammonia''

    For production of Ammonia.
    By Le Chatalier, the ideal conditions are high pressure and low temperature.
    High pressures are expensive to maintain and increase risk of explosion. A compromise pressure of 200 atmospheres is used.
    For temperature; if it was too low, the reaction would be too slow and actually slow down production. A compromise temperature of 500 degrees celsius is used.


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    #777
    xJEx
    Registered Users Posts: 166 ✭✭xJEx


    Deleted User wrote: »
    For production of Ammonia.
    By Le Chatalier, the ideal conditions are high pressure and low temperature.
    High pressures are expensive to maintain and increase risk of explosion. A compromise pressure of 200 atmospheres is used.
    For temperature; if it was too low, the reaction would be too slow and actually slow down production. A compromise temperature of 500 degrees celsius is used.

    Yeah I know but it was a rates question not a equilibrium


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    #778
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    xJEx wrote: »
    Yeah I know but it was a rates question not a equilibrium

    Sorry I just saw someone mention ammonia production.

    For what speeds up rate of reaction.

    1. Nature of reactants (are they both ionic or covalent) didn't apply to question
    2. Temperature of reaction
    3. Concentration of reactants
    4. Particle size didn't apply
    5. Presence of a catalyst


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    #779
    0mega
    Registered Users Posts: 850 ✭✭✭0mega


    xJEx wrote: »
    What answers did people get for Q3? I got .075 moles, then 4.347 for heat change and 57.96 for heat of reaction

    Same here but should it have been -57.96 for heat of reaction as it was exothermic and produced heat?


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    #780
    Jackobyte
    Registered Users Posts: 6,321 ✭✭✭Jackobyte


    Glee_GG wrote: »
    Gas I said "the flask appear to be hovering mid-air so you should put a tripod and gauze underneath" :L Its still true though even if I know they would have used it, they didn't put it in the picture!
    I said they had no water in with their cloves. :P The diagram definitely had more than one flaw so they'll have to be generous with the marking scheme on it.


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    #781
    [Deleted User]
    Posts: 0 ✭ [Deleted User]


    0mega wrote: »
    Same here but should it have been -57.96 for heat of reaction as it was exothermic and produced heat?

    Can I ask how you got the heat change? I had never done a question where the two initial temps were different so I added them both and divided by 2 but I'm guessing that was wrong?


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