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**Chemistry...Before/After

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    #692
    ShaunaMoll
    Registered Users Posts: 15 ✭ShaunaMoll


    It sounds like noone factored in this backwards arrow so they'll hardly mark us hard on it?


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    #693
    RedTexan
    Registered Users Posts: 217 ✭✭RedTexan


    And if you look at the question about the indicator and it's equilibrium, the arrows are in the same way?


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    #694
    leaveiton
    Closed Accounts Posts: 1,778 ✭✭✭leaveiton


    Surely it doesn't make a difference, there's still a forward reaction and a backwards reaction?


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    #695
    finality
    Registered Users Posts: 1,763 ✭✭✭finality


    RedTexan wrote: »
    And if you look at the question about the indicator and it's equilibrium, the arrows are in the same way?

    Exactly, that's what I was saying. That exact indicator equation is in chemistry live with the reactants and products at the same sides, but with the arrows going the normal way. :/


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    #696
    kyle84
    Registered Users Posts: 21 ✭kyle84


    id just stop worrying about it,everyone's probably ok. Any1 else enjoy the water question?


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    #697
    Mista
    Registered Users Posts: 183 ✭✭Mista


    kyle84 wrote: »
    id just stop worrying about it,everyone's probably ok. Any1 else enjoy the water question?

    Yes :D It was fantastic... :D


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    #698
    ivanh
    Closed Accounts Posts: 72 ✭✭ivanh


    ChemHickey wrote: »
    The top arrow was pointing backwards?


    It's bloody equilibrium! :L Of course there are two arrows! :L
    Never mind him, it doesn't matter what way the arrows point - the left hand side of any chemical equation is the reactants and the right is the products!


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    #699
    FaoiSin
    Registered Users Posts: 789 ✭✭✭FaoiSin


    kyle84 wrote: »
    id just stop worrying about it,everyone's probably ok. Any1 else enjoy the water question?

    I enjoyed all of the questions apart from the experiments tbh :D Water was a nice one. Organic was gorgeous. Shorts were nice and simple and Rutherford popped up as expected.


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    #700
    ivanh
    Closed Accounts Posts: 72 ✭✭ivanh


    What did ye say for the structural isomers?

    I said Propanone and Propanoic acid cause if you count all the C's H's and O's they have the same number of each :D


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    #701
    ivanh
    Closed Accounts Posts: 72 ✭✭ivanh


    What did ye say for the structural isomers?

    I said Propanone and Propanoic acid cause if you count all the C's H's and O's they have the same number of each :D


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    #702
    kyle84
    Registered Users Posts: 21 ✭kyle84


    Mista wrote: »
    Yes :D It was fantastic... :D
    thought there was a good mix of chemistry there,but of anions gettin in :)


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    #703
    leaveiton
    Closed Accounts Posts: 1,778 ✭✭✭leaveiton


    ivanh wrote: »
    What did ye say for the structural isomers?

    I said Propanone and Propanoic acid cause if you count all the C's H's and O's they have the same number of each :D

    Propanone and propanoic acid aren't isomers I don't think. I said propanone and propanal.


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    #704
    kyle84
    Registered Users Posts: 21 ✭kyle84


    ya its propanone propanal


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    #705
    Mista
    Registered Users Posts: 183 ✭✭Mista


    kyle84 wrote: »
    thought there was a good mix of chemistry there,but of anions gettin in :)

    I didn't get the chlorine bit.. I just said use a colourometer :L


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    #706
    ChemHickey
    Closed Accounts Posts: 3,479 ✭✭✭ChemHickey


    ivanh wrote: »
    What did ye say for the structural isomers?

    I said Propanone and Propanoic acid cause if you count all the C's H's and O's they have the same number of each :D

    Propanoic acid has an extra O no? I think so anyway.

    C2H5COCH2 = propanone

    C2H5COOH = propanoic acid.


    I may be wrong. Did them in my head.


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    #707
    partyatmygaff
    Registered Users Posts: 10,992 ✭✭✭✭partyatmygaff


    ivanh wrote: »
    What did ye say for the structural isomers?

    I said Propanone and Propanoic acid cause if you count all the C's H's and O's they have the same number of each :D
    They're not isomers unfortunately.

    Leaving aside the carbon backbone, there's an extra oxygen atom in a carboxylic acid.


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    #708
    ei.sderob
    Closed Accounts Posts: 108 ✭✭ei.sderob


    ChemHickey wrote: »
    Propanoic acid has an extra O no? I think so anyway.

    C2H5COCH2 = propanone

    C2H5COOH = propanoic acid.


    I may be wrong. Did them in my head.

    Nah, you're right. I used propanone and propanal myself. Haven't seen a question like that in the exam papers though. 1 test left!!!


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    #709
    ei.sderob
    Closed Accounts Posts: 108 ✭✭ei.sderob


    Apologies for the double post. Partyatmygaff, are you looking to going into lab work after graduation or sort of a behind the counter pharmacist role? I'm soooooooo undecided between Process and Pharmacy now lol. Need to make some sort of a decision soon.


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    #710
    ChemHickey
    Closed Accounts Posts: 3,479 ✭✭✭ChemHickey


    ei.sderob wrote: »
    ChemHickey wrote: »
    Propanoic acid has an extra O no? I think so anyway.

    C2H5COCH2 = propanone

    C2H5COOH = propanoic acid.


    I may be wrong. Did them in my head.

    Nah, you're right. I used propanone and propanal myself. Haven't seen a question like that in the exam papers though. 1 test left!!!

    Same here! It was a good question though!

    yep, I've one too! MUSIC! =e hopefully all will go well! =I


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    #711
    ei.sderob
    Closed Accounts Posts: 108 ✭✭ei.sderob


    ChemHickey wrote: »
    Same here! It was a good question though!

    yep, I've one too! MUSIC! =e hopefully all will go well! =I

    The excitement is well and truly building! All year I've had all the books I've needed to study layed out on my study desk and after each exam I've slowly started taking each book away, now only one book remains....it's going to be the most awesome sight when that table is bare.


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    #712
    ChemHickey
    Closed Accounts Posts: 3,479 ✭✭✭ChemHickey


    ei.sderob wrote: »
    ChemHickey wrote: »
    Same here! It was a good question though!

    yep, I've one too! MUSIC! =e hopefully all will go well! =I

    The excitement is well and truly building! All year I've had all the books I've needed to study layed out on my study desk and after each exam I've slowly started taking each book away, now only one book remains....it's going to be the most awesome sight when that table is bare.

    Haha, there is about 4 knee high columns of books in my room. We're almost there! =7


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    #713
    ei.sderob
    Closed Accounts Posts: 108 ✭✭ei.sderob


    ChemHickey wrote: »
    Haha, there is about 4 knee high columns of books in my room. We're almost there! =7

    I've sort of made a fort out of mine:D I can't wait to just procrastinate the whole summer and just not take advantage of the weather at all!


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    #714
    FaoiSin
    Registered Users Posts: 789 ✭✭✭FaoiSin


    Personally not looking forward to tidying the books. All in a massive pile in the corner of the room :pac:


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    #715
    reznov
    Registered Users Posts: 921 ✭✭✭reznov


    I'm reserving my books in case of repeating. :pac:


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    #716
    FaoiSin
    Registered Users Posts: 789 ✭✭✭FaoiSin


    reznov wrote: »
    I'm reserving my books in case of repeating. :pac:

    Stay optimistic reznov :P


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    #717
    reznov
    Registered Users Posts: 921 ✭✭✭reznov


    YeaaahFaoiSin wrote: »
    Stay optimistic reznov :P

    Chem was grand. :P Most of my subjects were except English and Maths. The ones I had to nail!

    It'll be grand. :cool:


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    #718
    Tankosaur
    Registered Users Posts: 102 ✭✭Tankosaur


    ShaunaMoll wrote: »
    Ugh, that's the first time i've ever seen the top arrow pointing backwards! Would they really be that mean? Could be a missprint?...please let it be a missprint..

    The question stated that the tri iodide ions were the products when iodide ions mixed with iodine so tri iodide was on the top for the calculation of kc.

    That value should be right, in this context.


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    #719
    FaoiSin
    Registered Users Posts: 789 ✭✭✭FaoiSin


    reznov wrote: »
    Chem was grand. :P Most of my subjects were except English and Maths. The ones I had to nail!

    It'll be grand. :cool:

    Yeah English and Maths were my worst also. Probably won't have to count English if I do well in Ag :) Chemistry was lovely


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    #720
    Tankosaur
    Registered Users Posts: 102 ✭✭Tankosaur


    finality wrote: »
    I don't think you're supposed to multiply by 2. Is this question 1? You're told it's a 0.05 molar solution - that's 0.05 moles per litre. It doesn't matter that you've only made 500cm^3 of it as it's still a 0.05 molar solution.

    Even if you got the moles per litre wrong, you'd still get the marks for the grams per litre provided your work for that part of the question was correct.

    The na2co3 is 0.05 M/ 500 cm^3 so the titration value you get for hcl most also be M/500cm^3 which came to 0.12 or summit like that.

    But the question asked for M/L so you must multiply by 2 and it comes to 0.24 Moles/litre


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    #721
    Liveforrugby
    Registered Users Posts: 343 ✭✭Liveforrugby


    finality wrote: »
    Some guy was saying that because the top arrow was pointing backwards you had to reverse the reaction and invert Kc. I disagree but he seemed quite adamant about it (and patronising).

    I don't know what patronising is but it sounds mean.

    As for Kc, that's the answer, I'm sorry if you didn't get it.

    It's the whole point of arrows, they indicate what the FORWARD reaction is, in the diagram going from left to right they gave you the backward reaction.

    That's the whole reason kc inverse was even discussed in chemistry live. If you didn't get it, hard luck, but don't bag me just because I told you that it was a bit of a trick question

    And I said you had to reverse the reaction OR inverse the Kc


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