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Chemistry build up and aftermath

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    #152
    Nihilist21
    Registered Users Posts: 131 ✭✭Nihilist21


    smndly wrote: »
    Q11 a v catalyst does not effect the value of Kc... not sure if that right though!
    :pac::pac::pac::pac:

    I said it increases the value for Kc, as it reduces the activation energy and so more ammonia is produced. I'm not 100% sure, but that's what I put down.


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    #153
    Fluorescence
    Moderators, Music Moderators Posts: 8,490 Mod ✭✭✭✭Fluorescence


    smndly wrote: »
    Right-o, heres a couple of my answers for comparison:

    Q.1 e (iii) 32.3% iron in the tablets

    Q8 d - 6% (w/v)

    (c) Relative Mr of neon = 20.19

    Q11 a v catalyst does not effect the value of Kc... not sure if that right though!
    :pac::pac::pac::pac:

    I got something different for the iron thing.... And 60% w/v *facepalm*.... I got the same Mr for Neon and I wrote that for Q11 too


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    #154
    Waaahhh
    Closed Accounts Posts: 55 ✭✭Waaahhh


    smndly wrote: »
    Right-o, heres a couple of my answers for comparison:

    Q.1 e (iii) 32.3% iron in the tablets

    Q4 f - pH of nitric acid = 1.6

    Q6 e - Heat of formation of C4H8 = -10 kj/mol^-1 ??? Bit weird i thought...

    Q8 d - 6% (w/v)

    Q10 (a) moles of chlorine = 1.5 moles

    (c) Relative Mr of neon = 20.19

    Q11 a v catalyst does not effect the value of Kc... not sure if that right though!
    :pac::pac::pac::pac:

    Yeh I got all that!


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    #155
    GA361
    Closed Accounts Posts: 609 ✭✭✭GA361


    smndly wrote: »
    Right-o, heres a couple of my answers for comparison:

    Q.1 e (iii) 32.3% iron in the tablets

    Q4 f - pH of nitric acid = 1.6

    Q6 e - Heat of formation of C4H8 = -10 kj/mol^-1 ??? Bit weird i thought...

    Q8 d - 6% (w/v)

    Q10 (a) moles of chlorine = 1.5 moles

    (c) Relative Mr of neon = 20.19

    Q11 a v catalyst does not effect the value of Kc... not sure if that right though!
    :pac::pac::pac::pac:

    Q1-Yep
    Q4-Yep
    Q6-Yep
    Q8-Yep
    Q10 a-I got 3.Divided the figure by avagadro's constant.Wat u do?
    Q10c-Yep


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    #156
    OxfordComma
    Closed Accounts Posts: 407 ✭✭OxfordComma


    Nihilist21 wrote: »
    I said it increases the value for Kc, as it reduces the activation energy and so more ammonia is produced. I'm not 100% sure, but that's what I put down.


    I thought it said in the book that a catalyst helps equilibrium be achieved more quickly but doesn't affect the overall position of equilibrium??

    These effing post mortems are making me so nervous!:eek:


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    #157
    Des23
    Closed Accounts Posts: 287 ✭✭Des23


    GA361 wrote: »
    But the dilution factor of 100 remains the same. . . . as there is only 25cm in that 2.5L sample

    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


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    #158
    yummy91
    Closed Accounts Posts: 80 ✭✭yummy91


    YAY!!! ITS OVER:D:D:D:D And it was a nice paper aswell,,, soooo happy, and the experiments were really good ones too!!!
    It was my last as well!!! so IM FREE!!!!!:D
    hope it went well for everyone else too:)


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    #159
    smndly
    Registered Users Posts: 215 ✭✭smndly


    1fahy4 wrote: »
    I think I got all of those!! Left out the ****ing units for delta H though:eek:... There goes a few marks...:(

    Id say it will only be one mark. Its not as if they were testing the you on the units because it was in the question. Id say itll be regarded as a slip

    Excellent paper IMO!! :cool:


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    #160
    OxfordComma
    Closed Accounts Posts: 407 ✭✭OxfordComma


    Oh yeah, is the main difference between the flames produced by ethyne and ethene that ethyne's flame is luminous but ethene's isn't??


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    #161
    GA361
    Closed Accounts Posts: 609 ✭✭✭GA361


    For Q5,did anyone else get
    d(i)-6
    d(ii)-10


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    #162
    Nihilist21
    Registered Users Posts: 131 ✭✭Nihilist21


    1fahy4 wrote: »
    I thought it said in the book that a catalyst helps equilibrium be achieved more quickly but doesn't affect the overall position of equilibrium??

    These effing post mortems are making me so nervous!:eek:

    Meh, bugger! Well thankfully that was the extra question I did, so probably wont be counted.


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    #163
    smndly
    Registered Users Posts: 215 ✭✭smndly


    GA361 wrote: »
    Q1-Yep
    Q4-Yep
    Q6-Yep
    Q8-Yep
    Q10 a-I got 3.Divided the figure by avagadro's constant.Wat u do?
    Q10c-Yep

    You have to divide by two aswell i think because its ATOMS of chlorine gas i.e Cl2. If it was molecules of chlorine gas you would just divide by avagadro's constant.... I think


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    #164
    GA361
    Closed Accounts Posts: 609 ✭✭✭GA361


    smndly wrote: »
    You have to divide by two aswell i think because its ATOMS of chlorine gas i.e Cl2. If it was molecules of chlorine gas you would just divide by avagadro's constant.... I think

    Was the question not how many moles of gas were present,as opposed to atoms?


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    #165
    CallMeDoctor
    Closed Accounts Posts: 48 ✭CallMeDoctor


    1fahy4 wrote: »
    Oh yeah, is the main difference between the flames produced by ethyne and ethene that ethyne's flame is luminous but ethene's isn't??

    I said ethyne had a sooty flame and ethene had a luminous flame?
    Think i got my A1:pac:

    Did ye say oxidising for the flame symbol?


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    #166
    Dmullar
    Closed Accounts Posts: 67 ✭✭Dmullar


    smndly wrote: »
    You have to divide by two aswell i think because its ATOMS of chlorine gas i.e Cl2. If it was molecules of chlorine gas you would just divide by avagadro's constant.... I think


    Yeah thats what I did... hope its right!


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    #167
    galway.gaa
    Closed Accounts Posts: 145 ✭✭galway.gaa


    in q1 why was it necessary to standardise the solutoin immeditly and what was the reagent used?
    why are iron tablets prescribed?


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    #168
    galway.gaa
    Closed Accounts Posts: 145 ✭✭galway.gaa


    CallMeDoctor wrote: »
    I said ethyne had a sooty flame and ethene had a luminous flame?
    Think i got my A1:pac:

    Did ye say oxidising for the flame symbol?
    whats the difference sooty or luminious? i wrote sooty


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    #169
    QueenOfLeon
    Closed Accounts Posts: 5,109 ✭✭✭QueenOfLeon


    galway.gaa wrote: »
    in q1 why was it necessary to standardise the solutoin immeditly and what was the reagent used?
    why are iron tablets prescribed?

    Emm, i said ammonium iron (ii) sulfate for the reagent, and anaemia for the reason they're prescribed. Dunno what the other one was tho...made a guess at it but i havent heard what the answer was...


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    #170
    galway.gaa
    Closed Accounts Posts: 145 ✭✭galway.gaa


    Anne-Marie!! wrote: »
    Emm, i said ammonium iron (ii) sulfate for the reagent, and anaemia for the reason they're prescribed. Dunno what the other one was tho...made a guess at it but i havent heard what the answer was...
    thats what i said too


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    #171
    Des23
    Closed Accounts Posts: 287 ✭✭Des23


    I think it was that KMnO4 decomposes in sunlight so it has to be used immediately, that was the only explanation I could think of... it was a nasty one though..


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    #172
    smndly
    Registered Users Posts: 215 ✭✭smndly


    Des23 wrote: »
    I think it was that KMnO4 decomposes in sunlight so it has to be used immediately, that was the only explanation I could think of... it was a nasty one though..

    Yea i said that too and i also said that if you left the solution too long some water would evaporate which would change the concentration of the solution. Although if you were smart you'd just put on a lid :P


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    #173
    GA361
    Closed Accounts Posts: 609 ✭✭✭GA361


    Anne-Marie!! wrote: »
    Emm, i said ammonium iron (ii) sulfate for the reagent, and anaemia for the reason they're prescribed. Dunno what the other one was tho...made a guess at it but i havent heard what the answer was...

    I did the same thing . . . . except I said ferrous ammonium sulfate:o . . . .They should both be acceptable . . .
    Like ye,I didn't get the other part
    For Qc did ye write 'to prevent Fe2+ being oxidised to Fe3+
    and for Qd was it 'to supply the H+ions?


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    #174
    Crystler
    Closed Accounts Posts: 120 ✭✭Crystler


    Just me or was that just not the most beautiful chemistry paper ever?


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    #175
    JSK 252
    Registered Users Posts: 1,257 ✭✭✭JSK 252


    GA361 wrote: »
    Was the question not how many moles of gas were present,as opposed to atoms?

    Exactly.


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    #176
    JSK 252
    Registered Users Posts: 1,257 ✭✭✭JSK 252


    GA361 wrote: »
    I did the same thing . . . . except I said ferrous ammonium sulfate:o . . . .They should both be acceptable . . .
    Like ye,I didn't get the other part
    For Qc did ye write 'to prevent Fe2+ being oxidised to Fe3+
    and for Qd was it 'to supply the H+ions?

    Also to allow full oxidation of the mn7+ to the Mn 2+ state. Otherwise a brown percipitate of Mn02 would have been formed.


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    #177
    JSK 252
    Registered Users Posts: 1,257 ✭✭✭JSK 252


    eoins2345 wrote: »
    Just wondering did ye get 32.03% for the the percentage by mass of iron in the tablets?
    -10 for the heat of formation ting?
    BOD of 510?
    In q10a did ye get 3 moles and in 10c 2.19?

    I got all those:)


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    #178
    GA361
    Closed Accounts Posts: 609 ✭✭✭GA361


    JSK 252 wrote: »
    Also to allow full oxidation of the mn7+ to the Mn 2+ state. Otherwise a brown percipitate of Mn02 would have been formed.

    Yeah I said about the brown prec too . . .


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    #179
    Polarity
    Registered Users Posts: 62 ✭✭Polarity


    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

    That's exactly what I did, hope it's right.

    For heat i also got -10 kj.. though i had that wrong til I looked on here. :P

    ****ed up the iron calulation.

    Got 6% for vinegar.


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    #180
    eoins2345
    Closed Accounts Posts: 154 ✭✭eoins2345


    awesome:)


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    #181
    eoins2345
    Closed Accounts Posts: 154 ✭✭eoins2345


    awesome!:)think chemistry is a subject you could really get an A in if ya applied yourself!


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