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    Finding unit 5 difficult for aqa
    Particularly the suggest questions of thermodynamics and redox.
    Always get confused between oxidising and reducing agent.


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    (Original post by Bloom77)
    Finding unit 5 difficult for aqa
    Particularly the suggest questions of thermodynamics and redox.
    Always get confused between oxidising and reducing agent.


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    Post the questions that you don't understand...
    An oxidising agent itself gets REDUCED
    A reducing agent itself gets OXIDISED
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    Chemistry exam day after tomorrow(toms bio) need so many prayers. I'm so worried...

    can anyone give me a brief on carbon 13 nmr? its new in our syllabus and ur teacher....... by the way its Alevel
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    (Original post by wb236)
    Hey, wondered if anyone could clear this up for me,

    Going over past papers for Chem6x I've come across drawing graphs for the Iodine clock reaction a few times, usually pretty straightforward, log (1/t) is plotted on the y-axis and Log(volume) on the x-axis, but I noticed in the mark scheme that says a mark is lost if the y-axis is plotted with ascending negative numbers? I'm not sure if the wording is awkward but the y-values for Log91/t) are usually negative, it doesn't seem to make sense to plot them in a descending scale (i.e. negative values getting more negative going up the y-axis),

    Cheers
    I guess going through examiner reports and seeing their so-called perfect answers can help!
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    I remember like this, oxidising agents are elements like OXYgen. Oxygen needs only 2 electrons to gain full shell stability so since it gains it gets reduced. If it gets reduced it oxidises others therefore its an oxidising agent

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    (Original post by wb236)
    Hey, wondered if anyone could clear this up for me,

    Going over past papers for Chem6x I've come across drawing graphs for the Iodine clock reaction a few times, usually pretty straightforward, log (1/t) is plotted on the y-axis and Log(volume) on the x-axis, but I noticed in the mark scheme that says a mark is lost if the y-axis is plotted with ascending negative numbers? I'm not sure if the wording is awkward but the y-values for Log91/t) are usually negative, it doesn't seem to make sense to plot them in a descending scale (i.e. negative values getting more negative going up the y-axis),

    Cheers
    I think that you have to plot the graph with the axis at the top if you see what i mean, so like a normal axis but upside down and then put your negative values on the y axis getting more negative as you go down
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    guys please help
    what happens if a piece if a piece of sodium is added to an alcohol
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    (Original post by A.S.J)
    Chemistry exam day after tomorrow(toms bio) need so many prayers. I'm so worried...

    can anyone give me a brief on carbon 13 nmr? its new in our syllabus and ur teacher....... by the way its Alevel
    AS or A2
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    http://www.thestudentroom.co.uk/show....php?t=4068049
    Help me you geniuses I am dying!!!!!
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    (Original post by Aimen.)
    Well the ideal solvent is the one in which solute dissolves most in hot solution and doesn't dissolve in cold solution at all. Since no solution is ideal, we use the solution in which most solution dissolves most in hot solution and least in cold solution, as in the one with greatest difference in the two solubility values.
    So now in this case, the difference in values of solution 1 is 5 whereas in solution 2 is 7.5 and as solution 2's difference > solution 1's difference so 2 is a better solvent.
    Well i hope it was a helpful explanation
    why must the solvent be hot though?


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    (Original post by Louisss)
    why must the solvent be hot though?


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    Is anyone here doing Chemistry AS Empa? Hoping its not too bad as some papers have been bad!
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    (Original post by djmans)
    AS or A2
    A2
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    (Original post by djmans)
    guys please help
    what happens if a piece if a piece of sodium is added to an alcohol
    Effervescence. Bubbling.
    the OH of alcohol becomes O- Na+
    If only Na solid then H2(g) released.
    If NaOH then H2O.
    Likewise.
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    Anyone got a really hard unit 5 aqa question from any of the exam papers?


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    Can someone help with the last part of this question please, the reaction with oxygen. Thanks!
    It's from the January 2012 AQA paper.
    Name:  ImageUploadedByStudent Room1462709288.608360.jpg
Views: 107
Size:  77.5 KB


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    (Original post by Louisss)
    why must the solvent be hot though?


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    To dissolve the solid for recrystallisation

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    Can someone help me with q9? It's about percentage error, and they've said in the answer that the titre will be 24.4 so you can use that.
    I've forgotten what the formulae for percentage error is ://
    http://filestore.aqa.org.uk/subjects...T-P10-TEST.PDF

    Thanks
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    How do you measure accurately the mass on an insoluble precipitate?

    and

    How can you use a more accurate end point of neutralisation reaction when an indicator is used?
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    (Original post by djmans)
    guys please help
    what happens if a piece if a piece of sodium is added to an alcohol
    hi there!

    according to my ccea revision guide, when sodium metal is added to say ethanol sodium ethoxide is produced and hydrogen.

    2 C2H5OH + 2Na ------------2 C2H5ONa + H2

    The sodium ethoxide produced belongs to a homologous series called "Alkoxides"
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    (Original post by A.S.J)
    Effervescence. Bubbling.
    the OH of alcohol becomes O- Na+
    If only Na solid then H2(g) released.
    If NaOH then H2O.
    Likewise.
    what about sodium carbonate
 
 
 
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