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    Na2S2O3.5H2HO How do you work out the oxidation number of sulphur in this question Please help!:confused:
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    also how do you work out the oxidation number of nitrogen in cu(no3)2????
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    (Original post by Kitnimohabbathai)
    guys help!!!!!!! question 3di from the may 2010 paper!?!! table on ionisation energies for aluminium...which ionisation energies represent removing electron from s subshell???? still have four past papers left
    I know that it is 2 and 3. But dont know why SOrry
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    I just dont seem to understand the roman numeral stuff....im gonna die if it comes up
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    (Original post by Freddy-Francis)
    I know that it is 2 and 3. But dont know why SOrry
    lol yeah the answers say either 2 and 3 or 10 and 11 but why??!?!?!
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    (Original post by Freddy-Francis)
    Same
    The roman numerals are simply the oxidation number of any element in the compound that can have varying oxidation numbers/ is not fixed such as oxygen or metals such as magnesium.
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    (Original post by Kitnimohabbathai)
    also how do you work out the oxidation number of nitrogen in cu(no3)2????
    Cu(NO3)2
    Take Brackets out

    CuN2O6
    Now do it.
    So O = -12
    Cu = +2
    Therefore N = 5
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    (Original post by Geronimo!)
    Na2S2O3.5H2HO How do you work out the oxidation number of sulphur in this question Please help!:confused:
    are you sure its 5H2H0? and not 5H20?
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    (Original post by Sara_A)
    I just dont seem to understand the roman numeral stuff....im gonna die if it comes up
    If you give me an example of a question you don't understand i could help?
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    how do you know copper is +2?
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    hey guys can someone please post the january 2013 paper and markscheme?
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    Study Helper
    Whose feeling prepared for this exam? I'm aiming for about 55+ in this one


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    (Original post by Kitnimohabbathai)
    are you sure its 5H2H0? and not 5H20?
    Na2S2O3

    O = -2 -2 -2 = -6
    Na = +1 +1 = +2
    Therefore S = +2 +2

    Sulphur = +2
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    (Original post by Kitnimohabbathai)
    how do you know copper is +2?
    Good question. I read it somewhere :P
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    (Original post by aa05)
    hey guys can someone please post the january 2013 paper and markscheme?
    Check back on page 2 or 8 i think. There is Markscheme and Question paper
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    Right time to start past papers :P
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    I managed to get a copy of the biology paper on tuesday, hopefully I'll get my hands on this chemistry paper tomorrow
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    (Original post by Freddy-Francis)
    Check back on page 2 or 8 i think. There is Markscheme and Question paper
    i can't find it on page 2 and there's no page 8 :P
    do you mind posting it
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    (Original post by Kitnimohabbathai)
    also how do you work out the oxidation number of nitrogen in cu(no3)2????

    (Original post by Freddy-Francis)
    Cu = +2
    Nitrogen is in the 5th group and so forms a 5+ ion. Copper has a variable oxidation state (along with the other transition metals) so don't rely on it always being 2+
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    • (Original post by Kitnimohabbathai)
      are you sure its 5H2H0? and not 5H20?

    yeh your right!
    its Na2S2O3 . 5H2O
 
 
 
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