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HL chemistry aftermath

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Comments

  • #92
    EuropeanSon
    Registered Users, Registered Users 2 Posts: 2,819 ✭✭✭EuropeanSon


    chaoticmess wrote: »
    Is that in Chemistry Live? :(
    I only wrote down pH buffer 10.... :(
    Our teacher explicitly told us it was ammonia, and said that another buffer of pH10 would affect the reaction and so shouldn't be used.

    I also remember it because I made the ammonia buffer up myself, and accidentally got a sniff of the ammonia, and the smell damn near blew my head off. Not something I'm likely to forget. :D


  • #93
    chaoticmess
    Closed Accounts Posts: 177 ✭✭chaoticmess


    EuropeanSon wrote: »
    Our teacher explicitly told us it was ammonia, and said that another buffer of pH10 would affect the reaction and so shouldn't be used.

    I also remember it because I made the ammonia buffer up myself, and accidentally got a sniff of the ammonia, and the smell damn near blew my head off. Not something I'm likely to forget. :D

    Oh ok. :( Ours never told us about the ammonia. :( Maybe I'll get half marks...!

    It may have helped if our teacher actually did the experiments with us...... :(


  • #94
    EuropeanSon
    Registered Users, Registered Users 2 Posts: 2,819 ✭✭✭EuropeanSon


    chaoticmess wrote: »
    Oh ok. :( Ours never told us about the ammonia. :( Maybe I'll get half marks...!

    It may have helped if our teacher actually did the experiments with us...... :(
    I know. That's one of the few our teacher did. We were in the labs for, at most, 1 double class per month.

    Most people probably didn't know it, so I'd say it'll marked easy.


  • #95
    zam
    Registered Users, Registered Users 2 Posts: 829 ✭✭✭zam


    EuropeanSon wrote: »
    Our teacher explicitly told us it was ammonia, and said that another buffer of pH10 would affect the reaction and so shouldn't be used.

    I also remember it because I made the ammonia buffer up myself, and accidentally got a sniff of the ammonia, and the smell damn near blew my head off. Not something I'm likely to forget. :D

    Oh dear. I work exclusively from IOE notes and never once was ammonia mentioned. Hopefully it'll be ok :(


  • #96
    chaoticmess
    Closed Accounts Posts: 177 ✭✭chaoticmess


    EuropeanSon wrote: »
    I know. That's one of the few our teacher did. We were in the labs for, at most, 1 double class per month.

    Most people probably didn't know it, so I'd say it'll marked easy.

    Every single one of our classes was in the lab as it's her "room" but she just didn't seem to enthusiastic about anything...! :( And there's nothing worse than a boring chemistry teacher for making you hate a subject...! I like it again now. :) haha!!

    Hopefully they'll mark it easy as I think I messed up the maths part of Q1 by accident.

    What answers did people get for that part??


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  • #97
    klose
    Registered Users Posts: 11,792 ✭✭✭✭klose


    _Exasperated_ wrote: »
    For the "What edta stands for" question they should allocate 1 mark for each correct word lol.

    I got the Tetra Acetic Acid bit right. I just guessed what E and D stood for. :) :cool:


    We had it drilled into us twas simple to learn
    Ethylene diamine tetra acetic acid, simple when you think first 2 parts rhyme haha:)
    It did come up before i think weather it was on old papers or old mock questions not sure,
    As for people wondering where bleach is (looked at it meself) i think predictions for l.c are worth sweet fanny adams from now on haha


  • #98
    klose
    Registered Users Posts: 11,792 ✭✭✭✭klose


    also the buffer solution?
    there was 3 questions on it, one was what is its use in this experiment which is grand to keep it at 10, the other question was what are they generally used for? i hazourded a guess to say keep phs at constant levels??? and the other was what would happen if the wrong type of buffer was used? eh hadent a clue about that now haha:rolleyes: im sure its in the book but just was overlooked by me ah well


  • #99
    hmmmm52
    Closed Accounts Posts: 26 ✭hmmmm52


    what did ye do for q.2 (d)?
    i said 7/8.9 x 100
    but for 12 marks that seemed a bit 2 easy. anyone any ideas?


  • #100
    FordieMUFC
    Closed Accounts Posts: 70 ✭✭FordieMUFC


    mark.oc wrote: »
    You had to take the volume of the container (100 litres) into account, so it was
    ((.75/100)(.75/100)) / (.25/100)
    which is .0225
    never thought of the 100L container... I got that right but couldn't figure out why other people were getting all wrong answers :confused::)
    lc2010 wrote: »
    Yeah you'll get the marks defo!;)
    for saying buffer 10 solution? :eek: aw ****, I thought of that but thought that it was just another way of saying the buffer is used to keep the PH around 10 :( aw well...


  • #101
    SnowPretzel
    Registered Users Posts: 69 ✭✭SnowPretzel


    hmmmm52 wrote: »
    what did ye do for q.2 (d)?
    i said 7/8.9 x 100
    but for 12 marks that seemed a bit 2 easy. anyone any ideas?

    It was a bit more complicated than that to be honest:(. You had to do it the same way you prove things in the ethanal/ethanoic acid experiments , e.g " Show that the sodium dichromate is the limiting factor". How I did it was I got the number of moles present in the glyceryl tristearate. It was .01 I think. Then i multiplied .01 by 3 (from the sodium stearate) and after that I multiplied the .03 by the relative molecular mass of sodium stearate. Then I put the actual yield over the theoretical yield and multiplied by 100... It was around 72% or something!


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  • #102
    Killio9
    Closed Accounts Posts: 48 ✭Killio9


    SnowPretzel wrote: »
    It was a bit more complicated than that to be honest:(. You had to do it the same way you prove things in the ethanal/ethanoic acid experiments , e.g " Show that the sodium dichromate is the limiting factor". How I did it was I got the number of moles present in the glyceryl tristearate. It was .01 I think. Then i multiplied .01 by 3 (from the sodium stearate) and after that I multiplied the .03 by the relative molecular mass of sodium stearate. Then I put the actual yield over the theoretical yield and multiplied by 100... It was around 72% or something!

    yeah i think i got something around that aswell...got the theoretical yield to be 8.82g or something?


  • #103
    SnowPretzel
    Registered Users Posts: 69 ✭✭SnowPretzel


    Killio9 wrote: »
    yeah i think i got something around that aswell...got the theoretical yield to be 8.82g or something?

    Yeah , that sounds familiar!:D


  • #104
    Screwedforlc
    Closed Accounts Posts: 16 ✭Screwedforlc


    What can i say...load of b***x i have done several years exam style and used the marking schemes to see hoe i got on...nothing lower then 80 percent and 85 in the press but won't even get a B


  • #105
    FordieMUFC
    Closed Accounts Posts: 70 ✭✭FordieMUFC


    :(:(:(:(
    Just went over the paper and realised that I never did the preparation of ethene questions in question 9! :( :mad::mad:
    How i left that out I dont know. 9 marks and all... :(:eek:
    seriously annoyed now at that :D
    I f***ing knew that question back to back all year, all the tests for unsaturation etc... and for 9 marks forget to draw a test tube, delivery tube, glass wool with ethanol and aluminium oxide being burned whilst collected in water :(
    serious kick to the balls, that brings my hopes of a B1 waaay down now unfortunately, I though I got around 48/50 in that question and all :mad:


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