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    (Original post by Relaxedexams)
    How many marks was that? Damn I said black solid disappears. Totally forgot iodine forms a purple solution with non polar solvents

    Maybe they will mark both since all iodine will not dissolve?

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    I think they'll mark...I had forgotten about that D:
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    How many marks was the iodo butane question and how much do they give the final Mark out of ,is it 100
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    (Original post by sahashuvo)
    Hydrogen Iodide has enough reducing power to reduce Concentrated Sulfuric acid so yield would be lower.
    Oops got that wrong...anyway thanks!!
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    (Original post by Relaxedexams)
    Error x2
    Therefore error is 1.

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    My teacher told me to never multiply by 2 for the new exams cause i did that in my mock n got it wrong . Omg no. Serious like for sure?
    thanx though
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    (Original post by Relaxedexams)
    Yep. That is what I got. % error = 2.15? And you rounded it to 2.2?

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    I got 2.19 something so i kept it to 2s.f. Will i still get the mark?What do u reckon?
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    (Original post by awesomesoccerfan)
    I got 2.19 something so i kept it to 2s.f. Will i still get the mark?What do u reckon?
    Im guessing you used 47 as temperature change? I used temperature change of solution. Either way they will most probably award marks.

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    (Original post by rockstar101)
    My teacher told me to never multiply by 2 for the new exams cause i did that in my mock n got it wrong . Omg no. Serious like for sure?
    thanx though
    You have to take two temperature readings, so there will be 2 errors of 0.5. Total error = 2 (0.5)=1

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    (Original post by Relaxedexams)
    Im guessing you used 47 as temperature change? I used temperature change of solution. Either way they will most probably award marks.

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    I used 45.6(actual difference used during enthalpy change calculation). 1/45.6 x 100 and got 2.19.
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    (Original post by awesomesoccerfan)
    I used 45.6(actual difference used during enthalpy change calculation). 1/45.6 x 100 and got 2.19.
    That is what I did. Maybe I got 2.19 as well

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    When drawing the distillation are we allowed to use a pencil??? :O


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    Yes of course!


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    For the question 'why thiosulfate is used to wash the mixture instead of water', is it because iodobutane does not mix with water so it cannot be washed? If you reckon my answer is wrong, what's your answer?
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    (Original post by MrNevermind)
    For the question 'why thiosulfate is used to wash the mixture instead of water', is it because iodobutane does not mix with water so it cannot be washed? If you reckon my answer is wrong, what's your answer?
    The only places thiosulphate exists in our specs is in reaction of halogens and iodometric titrations (iodine with thiosulpate).
    So to remove unreacted iodine by reduction to iodide ions which dissolves in the aqueous layer and can be removed by separation.
    So answer is adding just water does not dissolve iodine but thiosulphate solution does.

    Always reflect the specification, or is there another answer?

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    Hey do any of you have the question paper like for bio it was posted up. Pls post this one as well. I just want to clarify some question. Thanx in advance can i find it on scribd?
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    What's the empirical formula in the first question ?


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    (Original post by Tamerdakkak)
    What's the empirical formula in the first question ?


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    C3H8O or C3H7OH

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    (Original post by KhawlaM)
    You are probably right. I forgot about the organic solvent, so I wrote instead that the brown color will disappear :s


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    hey alcohol is polar right?? it can form hydrogen bonds with water..when iodine dissolves in polar solvents it gives a brown color. so shouldnt it be brown???
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    (Original post by Relaxedexams)
    You have to take two temperature readings, so there will be 2 errors of 0.5. Total error = 2 (0.5)=1

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    if you take the temperature difference wont the error cancel out? i mean 100-0 is 100 and 101-1 is also a hundred. so even if error was present in the thermometer reading the temperature difference obtained would still be accurate right??
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    What's the answer for the "why do we use dilute sodium thiosulphate solution instead of water?" question??

    AND BTW..i failed in my physics unit3B exam... TT____TT
    I made ONE mistake and it cost my whole ques...I'm crying sooo much nowwww..
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    can any1 pls tell me what to read on chemistry unit 1?
 
 
 
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