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    (Original post by karsh)
    yepp... all my mates got 10 for no of moles of H2O! anybody with any relevant calculations?!

    ummmm you cant work this out just using maths, i assume you did the titration...

    im going to do some preliminary work next week, can you tell me if you found any problems that i should watch out for?
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    it only says to work out moles of H2O from calculations for method 1... heating, not titration.

    and... i dont know how the calculations doing the titration method... we havnt yet done the experiment, and we are not supposed to at our college!

    so how am i supposed to work it out? with the titration?
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    it is possible with both methods, otherwise what would be the point in planning a titration??

    thermal decomp is easy stuff.

    titration took some thought but all you gotta do is:
    weight some crystals
    dissolve them
    titrate to find molarity na2co3
    find mass na2co3
    find mass water in original cyrstals
    find no. moles water

    you can put the pieces together with that...

    no you arnt MENT to do the experiment, its only a plan. but if you do prelim work you have a better idea of what to do and how to do it.
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    thanks... although that was some help, i wish we did the prelim. we have to give it in on friday.. does anybody have longer than that?
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    i have til the 10th i think. my college doesnt give out the planning until just before the practical.
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    Hmm. Apart from suggesting thousands of repeats, what flaws are people pointing out in Evaluation of thermal decomp and titration? Chemistry's just too darn accurate!!! In the Bio planning I could have written a 1000 words just on how many errors there were in the technique and method!
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    Hmm. Apart from suggesting thousands of repeats, what flaws are people pointing out in Evaluation of thermal decomp and titration? Chemistry's just too darn accurate!!! In the Bio planning I could have written a 1000 words just on how many errors there were in the technique and method!
    ive got a slight idea on some errors:
    here i go,
    Titration nozzle was not flush with the mouth titration tube, this means I think these are when you are meant to run the burrette through with the substance to stop air bubbles making the experiment inaccurate,
    air bubles in the pipette.
    when using the funnel to fill the burette make sure you take it off because it might have an extra drop of woteva you using
    sample contamination
    burette is dirty, wash it out (not with fairy, like sme1 did in the other class
    !!)

    thats all i think of at the top me head!

    any more?
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    Lol! I'll steer well clear of that Fairy then! Thanks
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    only measure mass to 2 decimal places. even if your balance can do 3.
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    Lol! I'll steer well clear of that Fairy then! Thanks
    glad to help someone.

    im suppose to hand mine in on monday the 8th. Not very long.
    can someone please help me in what to write in the introduction.
    i just dont know what to write about it?
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    (Original post by suzukiescudo)
    glad to help someone.

    im suppose to hand mine in on monday the 8th. Not very long.
    can someone please help me in what to write in the introduction.
    i just dont know what to write about it?
    Talk about the bonding between carbonate ion and sodium.. and the bonding between water of crystallisation and sodium carbonate. Research it! Talk about group 1 and trends for melting points.. decomposition.. Go on Wiki!
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    isnt that too much for the research? becuase its only 800 words max!
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    (Original post by karsh)
    isnt that too much for the research? becuase its only 800 words max!
    Probably. But you can describe all of that very briefly. Even mentioning 'key words' gets you your marks. It doesn't have to be much more than a paragraph. Don't ask me.. I always play truant with word limits by putting everything in tables so they don't count it!
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    Talk about the bonding between carbonate ion and sodium.. and the bonding between water of crystallisation and sodium carbonate. Research it! Talk about group 1 and trends for melting points.. decomposition.. Go on Wiki!
    is decomposition, are talking about thermal decomposition?
    water crytallisation? isnt that ice?
    im confused!
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    i did my calculations again and i have found out that i have done it completely wrong!! soB..sob

    someone mentioned its either: Na2Co3.xH2O
    x=10
    x=7

    I have got 10. not8!

    now whos the clever calculation person to check if im right?
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    (Original post by cordelia)
    urm well here are the two perfect methods (we did this experiment for the evaluation and analysis skill) i dont know if it will help but anyways, here we go:

    Method 1:
    1. Using a balance that weighs to two decimal places, weigh a crucible. Add between 1.30 – 1.50 g of hydrated iron II sulphate crystals. Record the masses.
    2. Place the crucible containing the hydrated iron(II) sulphate crystals on the pipe-clay triangle and gently heat for about two minutes. The heating should be carried out in either a fume cupboard or a well-ventilated room.
    3. Allow to cool and weigh the crucible and the iron(II) sulphate.
    4. Repeat steps 2 and 3.
    5. Record all of the masses.
    Method 2: Titration
    1. Weigh as accurately as possible between 2.85 and 3.10 g of hydrated iron(II) sulphate crystals, FeSO4.xH2O. Record the mass and then dissolve the crystals in 50.0 cm3 of 1 mol dm-3 H2SO4(aq) and make up to 250 cm3 in a volumetric flask with distilled water. Invert the volumetric flask several times to ensure that the solution is evenly mixed.
    2. Using a pipette filler, pipette 25.0 cm3 of the solution of iron(II) sulphate into a conical flask and add approximately 20.0 cm3 of the 1 mol dm-3 H2SO4(aq) solution provided.
    3. Titrate the acidified Fe2+(aq) solution with 0.0100 mol dm-3 potassium permanganate, KMnO4(aq), and continue the titration to the normal end-point.
    4. Repeat the titration until you have obtained concordant results
    Method two does NOT apply to the plan. It will just change the FE2 to FE3 check out chemguide.co.uk

    Also beware that 'Wiki' can be edited by people and is not always correct, most of the info can be found in the textbook, look there first!
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    wiki has never proved to be wrong in anything ive ever researched, but your right that you shouldnt just have wiki as your resource. all good science plans should have minimum of 5 sources.
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    (Original post by suzukiescudo)
    i did my calculations again and i have found out that i have done it completely wrong!! soB..sob

    someone mentioned its either: Na2Co3.xH2O
    x=10
    x=7

    I have got 10. not8!

    now whos the clever calculation person to check if im right?
    I have already said this, but how can we check if your calculations are right if you don't explain how you got 8 or 10? My psychic powers aren't that amazing!

    Sodium carbonate does have three known hydrated forms; monohydrate, decahydrate and heptahydrate. (that's 1, 10 and 7)

    Water of crystallisation is not ice, it is the water contained in a crystalline salt. You'll need to read up about this. You won't get all your marks unless you can quote sources of research other than your textbook.. so you might as well just look it up and read about it. It doesn't take long!
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    (Original post by mubarak_elmubarak)
    Method two does NOT apply to the plan. It will just change the FE2 to FE3 check out chemguide.co.uk

    Also beware that 'Wiki' can be edited by people and is not always correct, most of the info can be found in the textbook, look there first!
    Cordelia's prelim practical from college is not going to be exactly the same as the experiment we're meant to design.. but it is helpful as something to mention for prelim work, and there are similarities that can be adapted.

    Wikipedia is screened before people's additions are accepted, and it quotes the resources and the people who submitted the additions at the bottom of each page. Usually its University professors when I've glanced down on the science entries..
    At any rate, OCR wouldn't blame us if the source we use is not entirely reliable.. as long as we're not contradicting what we should know from AS.

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    (Original post by suzukiescudo)
    i did my calculations again and i have found out that i have done it completely wrong!! soB..sob

    someone mentioned its either: Na2Co3.xH2O
    x=10
    x=7

    I have got 10. not8!

    now whos the clever calculation person to check if im right?

    LOL, please PM me your maths. As far as i can see you cant work this out mathematically as you dont know the no. moles of Na2CO3.

    you do the thermal decomp/tritration to work this value out. then you can do the maths.
 
 
 
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