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** Chemistry 2017

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  • 15-06-2017 3:36pm
    #1
    Registered Users Posts: 946 ✭✭✭


    Does anyone here do chemistry? Do you know is this experiment still on the course? I can't find it in the book. It's 2007 Q2. A sample of ethanoic acid (CH3COOH) was prepared by the oxidation of ethanol using the apparatus shown.


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  • Registered Users Posts: 157 ✭✭gavinoontheweb


    daraghwal wrote: »
    Does anyone here do chemistry? Do you know is this experiment still on the course? I can't find it in the book. It's 2007 Q2. A sample of ethanoic acid (CH3COOH) was prepared by the oxidation of ethanol using the apparatus shown.


    Latest changes to LC Chem in here, http://www.gillmacmillan.ie/AcuCustom/Sitename/DAM/060/LSMS_Chemistry_Changes_to_the_Experimental_Work.pdf
    Hoping for Iron/Bleach, Soap/Eugenol, Volatile Liquid on experiments


  • Registered Users Posts: 244 ✭✭hasdanta


    daraghwal wrote: »
    Does anyone here do chemistry? Do you know is this experiment still on the course? I can't find it in the book. It's 2007 Q2. A sample of ethanoic acid (CH3COOH) was prepared by the oxidation of ethanol using the apparatus shown.

    It's not on the course anymore.


  • Registered Users Posts: 746 ✭✭✭Mr Rhode Island Red


    daraghwal wrote: »
    Does anyone here do chemistry? Do you know is this experiment still on the course? I can't find it in the book. It's 2007 Q2. A sample of ethanoic acid (CH3COOH) was prepared by the oxidation of ethanol using the apparatus shown.

    As far as I know anything involving chromates and dichromates was taken off the course. We don't have to know the preparation of ethanoic acid but we do have to know it's properties.


  • Registered Users Posts: 22 Skodaa


    I was pretty good at Chemistry during 5th year mainly because of the teacher but that teacher took a teaching job in Dubai for 6th year and the replacement hasn't be great so I really fell off, does anyone have good topics to look over for the exam? please and thanks


  • Registered Users Posts: 646 ✭✭✭i am awsome


    Atomic Theory & Organic make up half (or even more) of the exam, focus on those. Q1 - study the experiments, pretty much guaranteed 50marks Q2 - study organic experiments, also guaranteed 50 marks. Q4 - short Q's, know your definitions (eg: Le Chatelier's Principal, v. frequent)


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  • Registered Users Posts: 946 ✭✭✭daraghwal


    Q5 is always atomic theory, Q6 is always fuels and heats of reactions mixed with a bit of organic. You're almost guaranteed a bit on water and then the reaction schemes almost always come up too.


  • Registered Users Posts: 22 Skodaa


    does anyone have the DEB chemistry pre marking schemes? or answers mostly correct?


  • Registered Users Posts: 85 ✭✭Ponguin


    Skodaa wrote: »
    does anyone have the DEB chemistry pre marking schemes? or answers mostly correct?

    Not sure whether mine is DEB or Examcraft, it has volatile liquids and iron tablets I think?


  • Registered Users Posts: 157 ✭✭gavinoontheweb


    ethbr2mech1.GIF
    ethhclmech.GIF
    Does anyone know if diagrams like these are suitable for the mechanism of ionic addition, I'm fairly certain it will come up tomorrow?


  • Registered Users Posts: 205 ✭✭thetalker


    seems alright, make sure to have explanations and a heading for each.

    Anyone revising for any specific exp? I don't actually know a lot of them (poor teacher) and was hoping to focus on a few.
    So far I've done the iron tablet, clove oil, ethene and ehtyne, the bleach one, volatile liquid, oh and water hardness.

    Any other biggies people imagine?


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  • Registered Users Posts: 946 ✭✭✭daraghwal


    thetalker wrote: »
    seems alright, make sure to have explanations and a heading for each.

    Anyone revising for any specific exp? I don't actually know a lot of them (poor teacher) and was hoping to focus on a few.
    So far I've done the iron tablet, clove oil, ethene and ehtyne, the bleach one, volatile liquid, oh and water hardness.

    Any other biggies people imagine?

    Soap?


  • Registered Users Posts: 205 ✭✭thetalker


    Looks like the iron tablet and ethene/ethyne came up so that was grand.
    What did people get for the Kc value and that question on the acids. Wasn't too sure on those.


  • Registered Users Posts: 85 ✭✭Ponguin


    thetalker wrote: »
    Looks like the iron tablet and ethene/ethyne came up so that was grand.
    What did people get for the Kc value and that question on the acids. Wasn't too sure on those.

    Think I got around 0.732 mol/l of product in reaction vessel for the Kc one!


  • Registered Users Posts: 205 ✭✭thetalker


    Same! But a friend pointed out you have 2 moles on the right so maybe you had to multiply that by two?


  • Registered Users Posts: 85 ✭✭dorado99


    Did anyone else use the factor formula, then discarded negative value and use the positive value?


  • Registered Users Posts: 85 ✭✭Ponguin


    No I think that's accounted for when you use the equilibrium constant formula as the [No2] or whatever was squared, I hope


  • Registered Users Posts: 85 ✭✭Ponguin


    dorado99 wrote: »
    Did anyone else use the factor formula, then discarded negative value and use the positive value?

    Yeah I used the -b


  • Registered Users Posts: 85 ✭✭dorado99


    i got x/20 for product which was squared to get x^2/400 then 1-x for thereactant. So put that into kc you have a variable ^2


  • Registered Users Posts: 7,054 ✭✭✭wanderer100


    Ponguin wrote: »
    Yeah I used the -b

    Yeah so did I


  • Registered Users Posts: 946 ✭✭✭daraghwal


    I got this? Is that not right?


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  • Registered Users Posts: 205 ✭✭thetalker


    dorado99 wrote: »
    i got x/20 for product which was squared to get x^2/400 then 1-x for thereactant. So put that into kc you have a variable ^2

    Why x/20?


  • Registered Users Posts: 205 ✭✭thetalker


    daraghwal wrote: »
    I got this? Is that not right?

    0.1 is what you put in, at equilibrium it will be 0.1-x as in whatever it loses and turns into the product


  • Registered Users Posts: 85 ✭✭Ponguin


    My formula was X^2 +2X -2 =0 so whatever the positive root is of that I got


  • Registered Users Posts: 85 ✭✭dorado99


    thetalker wrote: »
    Why x/20?

    the Ec value was X/2 /10 . Since there is a 2 in front of the product , the change in equilibrium and in turn at equilibrium the value is x/2 . Then divide it by the number of litres which is 10. So 0.5x/10 is x/20.


  • Registered Users Posts: 1,316 ✭✭✭Consonata


    thetalker wrote:
    0.1 is what you put in, at equilibrium it will be 0.1-x as in whatever it loses and turns into the product

    Was it not be 1 - x at equilibrium and then divided by 10 to get 0.1 - 0.1x


  • Registered Users Posts: 746 ✭✭✭Mr Rhode Island Red


    Anybody get 32 for the relative molecular mass of the volatile liquid in question 10?

    Not a bad paper, thought Q4 was fierce tricky compared to how straightforward it normally is.


  • Registered Users Posts: 85 ✭✭dorado99


    Did you guys get a positive number in hundreds (+100s) for Hess' calculation?


  • Registered Users Posts: 205 ✭✭thetalker


    Anybody get 32 for the relative molecular mass of the volatile liquid in question 10?

    Not a bad paper, thought Q4 was fierce tricky compared to how straightforward it normally is.
    I got something around that yeah

    First 6 questions were nice, the other two Q9 and Q10 for me, were a bit trickier.


  • Registered Users Posts: 85 ✭✭Ponguin


    Not a bad paper, thought Q4 was fierce tricky compared to how straightforward it normally is.
    Yeah usually I do all the short questions with hardly any bother but today only did 9 I think, some of them like the eugenol one looked fairly tricky at first glance but turned out to be okay in the end :)


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  • Registered Users Posts: 83 ✭✭Manufan123


    dorado99 wrote: »
    Did you guys get a positive number in hundreds (+100s) for Hess' calculation?

    Yes around 180 rings a bell


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