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Chemistry build up and aftermath

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    #182
    CptnRed
    Closed Accounts Posts: 7 ✭CptnRed


    I got -10 too, I thought i was wrong but i also nearly left it at +10.
    I did crap in question 1 but happy enough with the rest of it, hoping for an a2/b1 if i hadnt have left it until the night before to study i cuda got an a1 no bother, I'm a fool!


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    #183
    JSK 252
    Registered Users Posts: 1,257 ✭✭✭JSK 252


    Des23 wrote: »
    Yeah maybe, the way I saw it was that:
    The BOD you got was 5.1.
    But that is for 2.5 liters
    divide 5.1 by 2.5 = 2.04 ppm in a liter.
    multiply by dilution factor of 100
    ppm = 204

    The dilution was factor was carried out PRIOR to measuring the BOD of the sample(s).

    Check pg275 of chemistry live for an example.


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    #184
    aine-maire
    Closed Accounts Posts: 456 ✭✭aine-maire


    :) <I'm so happy!

    Got all the answers that seem to be repeating on this thread... Also had loooads of time, so I did 10 questions (kinda stupid I know but whatever...)

    Q3 was beautiful! Did the 3 experiments anyway,lovely questions I thought, didn't miss bleach one bit :D


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    #185
    JSK 252
    Registered Users Posts: 1,257 ✭✭✭JSK 252


    aine-maire wrote: »
    :) <I'm so happy!

    Got all the answers that seem to be repeating on this thread... Also had loooads of time, so I did 10 questions (kinda stupid I know but whatever...)

    Q3 was beautiful! Did the 3 experiments anyway,lovely questions I thought, didn't miss bleach one bit :D

    Bleach lives on to fight another day!:)


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    #186
    eoins2345
    Closed Accounts Posts: 154 ✭✭eoins2345


    where is the rates of reactions experiment in chemistry live or is it there at all?


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    #187
    aine-maire
    Closed Accounts Posts: 456 ✭✭aine-maire


    I didn't do that question, but I think it's mentioned under heterogenous catalysis, no?


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    #188
    Des23
    Closed Accounts Posts: 287 ✭✭Des23


    JSK 252 wrote: »
    The dilution was factor was carried out PRIOR to measuring the BOD of the sample(s).

    Check pg275 of chemistry live for an example.

    Yeah I think I've seen where I went wrong now, I was saying that the values of ppm were for 2.5 litres, but by definition ppm is mg/L, ****, I had it right the first time but went back and changed it. :mad:

    Oh well, I did 10 questions anyway..


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    #189
    Idjit
    Registered Users Posts: 853 ✭✭✭Idjit


    i did ordinary level chem. I was sooo nervous when i went in and i had almost crossed chem off as a subject to count for points..but now i think i at least got a b3!Amazing! all that study and crammin paid off!:D


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    #190
    mikeglee
    Closed Accounts Posts: 127 ✭✭mikeglee


    I wanna kill chemsitry


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    #191
    ayumi
    Registered Users Posts: 676 ✭✭✭ayumi


    that chemistry paper was much better,it looks straight forward and no tricky parts,if you study you will get a B1 or A2
    for a higher level paper its better then other years


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    #192
    OxfordComma
    Closed Accounts Posts: 407 ✭✭OxfordComma


    eoins2345 wrote: »
    where is the rates of reactions experiment in chemistry live or is it there at all?


    It's on pg.223... I hadn't even studied that example but I vaguely remembered the fact that the wire glowed... God knows how I managed to recall that. It looked strange but it was one of the easiest questions in section b once you got your head around it!


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    #193
    Piste
    Registered Users Posts: 11,440 ✭✭✭✭Piste


    Chemistry was really nice I thought, I got most of the answers people seem to be saying, especially for the maths bits which I thought might be a bit dodge. I got 1.5 for the moles of chlorine, I think I multiplied the no of atoms by 2 to get the no of molecules, then used that no to find the moles. Or something.

    For the KMnO4 question about why you should use the solution immediately, I said cos it decomposes in the presence of sunlight, but it was a bit of a guess.

    For the ways in which hydrocarbons are tinkered around with in the oil refinery I said polymerisation...is that right?


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    #194
    Fringe
    Registered Users Posts: 1,082 ✭✭✭Fringe


    1fahy4 wrote: »
    It's on pg.223... I hadn't even studied that example but I vaguely remembered the fact that the wire glowed... God knows how I managed to recall that. It looked strange but it was one of the easiest questions in section b once you got your head around it!

    Yeah same! Don't remember that experiment at all except for the picture on the page with the glowing spring thing. That was all that popped into my head. I said the platinum glows an orangey bright colour. We did plenty of iodine snakes, cobalt chlorides and dust explosions but our teacher never did that one. What did people say the products were? I assumed that methanol reacts with oxygen to form CO2 and H2O.


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    #195
    OxfordComma
    Closed Accounts Posts: 407 ✭✭OxfordComma


    Fringe wrote: »
    Yeah same! Don't remember that experiment at all except for the picture on the page with the glowing spring thing. That was all that popped into my head. I said the platinum glows an orangey bright colour. We did plenty of iodine snakes, cobalt chlorides and dust explosions but our teacher never did that one. What did people say the products were? I assumed that methanol reacts with oxygen to form CO2 and H2O.


    Because it said it was being oxidised, I went the route of
    alcohol -->aldehyde -->carboxylic acid, like the oxidation of ethanol...

    So I said the products were methanal and methanoic acid. I'm probably wrong:(


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    #196
    Aisling(",)
    Registered Users Posts: 6,393 ✭✭✭Aisling(",)


    its done
    i dont care anymore
    yay


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    #197
    wexhurdler
    Closed Accounts Posts: 83 ✭✭wexhurdler


    Piste wrote: »

    For the ways in which hydrocarbons are tinkered around with in the oil refinery I said polymerisation...is that right?

    you could be right mate.. I said reforming and isomerisation..

    its was a fair paper.. delighted that salts and anions tests came up..

    was really hoping for an A1 made a few stupid mistakes nd probably was a few marks short but hey who knows...

    last exam:D delighted:D Q6 c.... speaking of whiskey....:P:pac:


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    #198
    Col Man
    Registered Users Posts: 92 ✭✭Col Man


    An alternative explanation (unnecessary, but err me) is that it was 5.1 ppm used, so that's in one litre (5.1 mg/L). We had 2.5 litres, so that's 12.75 mg. So that's 12.75 mg / 25cm^3, cos that's how much of the original sample we had. Which is 510 mg / litre of the original sample, so 510 ppm. Good times


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    #199
    Nihilist21
    Registered Users Posts: 131 ✭✭Nihilist21


    Fringe wrote: »
    What did people say the products were? I assumed that methanol reacts with oxygen to form CO2 and H2O.

    I said the products were CO2 and H2 (as I think I recall that thats why the platinum glows), however I could be completely wrong.


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    #200
    GA361
    Closed Accounts Posts: 609 ✭✭✭GA361


    wexhurdler wrote: »
    you could be right mate.. I said reforming and isomerisation..

    its was a fair paper.. delighted that salts and anions tests came up..

    was really hoping for an A1 made a few stupid mistakes nd probably was a few marks short but hey who knows...

    last exam:D delighted:D Q6 c.... speaking of whiskey....:P:pac:

    I said reforming and isomerisation too . . .

    Ha ha about the whiskey,wouldn't mind a bit of Southern Comfort now ha ha :D


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    #201
    smndly
    Registered Users Posts: 217 ✭✭smndly


    GA361 wrote: »
    I said reforming and isomerisation too . . .

    Ha ha about the whiskey,wouldn't mind a bit of Southern Comfort now ha ha :D

    Sorry to rain on the parade but isomerisation is a type of reforming. The answer for the question i think is: isomerisation and dehydrocyclicisation (making the hydrocarbons ring shaped). Reforming is an umbrella term for these although they may still give marks for it.


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    #202
    eoins2345
    Closed Accounts Posts: 154 ✭✭eoins2345


    Nihilist21 wrote: »
    I said the products were CO2 and H2 (as I think I recall that thats why the platinum glows), however I could be completely wrong.

    http://www2.uni-siegen.de/~pci/versuche/english/methanol.html


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    #203
    Col Man
    Registered Users Posts: 92 ✭✭Col Man


    smndly wrote: »
    Sorry to rain on the parade but isomerisation is a type of reforming. The answer for the question i think is: isomerisation and dehydrocyclicisation (making the hydrocarbons ring shaped). Reforming is an umbrella term for these although they may still give marks for it.


    No, reforming is dehydrocyclisation, it's not an umbrella term. So you were right with your answers, and they were also right, because they were the same answers! Oh good times.


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    #204
    OxfordComma
    Closed Accounts Posts: 407 ✭✭OxfordComma


    Reforming is the same as dehydrocyclisation. Check the textbook...


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    #205
    not bakunin
    Registered Users Posts: 265 ✭✭not bakunin


    went in.............raped the paper..............came out.

    the deed is done. yes.


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    #206
    sponge-97
    Closed Accounts Posts: 25 ✭sponge-97


    Oh god who cares! It's done! It's was thoug enough, but just because it's chemistry. Other than that, nice enough paper! I think most people saw the flame and anion tests were like "What the-? OHHHH? " And then it was a breeze!


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    #207
    Homicidal_jesus
    Closed Accounts Posts: 529 ✭✭✭Homicidal_jesus


    oh what a sweet paper!!!short questions were easy have they ever used safety symbols before?..strange how the used 2 experiments for each q in 2 and 3 but happy its over and done with...P.A.R.T.Y


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    #208
    Adriatic
    Registered Users Posts: 484 ✭✭Adriatic


    YAY I'm finished, all I liked were the experiments in higher level but I just want to scrape a pass to get by.


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    #209
    JSK 252
    Registered Users Posts: 1,257 ✭✭✭JSK 252


    1fahy4 wrote: »
    Reforming is the same as dehydrocyclisation. Check the textbook...

    You could also say the addition of oxygenates. Basically all the ways the octane number of a fuel is increased.


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    #210
    Occono
    Registered Users Posts: 1,093 ✭✭✭Occono


    I'm finally done too. Wish I had finished with something I'm better at. Don't know how to celebrate, I'm an Introvert so probably just play games and DVDs...

    Have to sort out my CAO though now, I have four course marked but I should probably add a good few more while there's time.


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    #211
    Col Man
    Registered Users Posts: 92 ✭✭Col Man


    Homicidal_jesus wrote: »
    short questions were easy have they ever used safety symbols before?


    Well, 2008:

    "Hydrogen peroxide solution is an oxidising reagent. Draw or describe the warning symbol put on a container of hydrogen peroxide solution to indicate this hazard."

    So I guess yeah?


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