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    Anyone have any tips on unstructured titrations?! Honestly can't do them and they are usually worth 7 marks! Thanks


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    (Original post by fayled)
    That is what I wrote
    oops, lol what a silly billy
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    Concentrated nitric acid is a powerful oxidising agent. Concentrated nitric acid oxidises
    sulphur to sulphuric acid. Nitrogen dioxide and another product are also formed.
    (i) Suggest a balanced equation for this reaction.

    For this question i got the correct reactant and product but the balancing is hard, how would you do it?

    HNO3 + S ---> H2SO4 + NO2 + H20
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    (Original post by otrivine)
    Concentrated nitric acid is a powerful oxidising agent. Concentrated nitric acid oxidises
    sulphur to sulphuric acid. Nitrogen dioxide and another product are also formed.
    (i) Suggest a balanced equation for this reaction.

    For this question i got the correct reactant and product but the balancing is hard, how would you do it?

    HNO3 + S ---> H2SO4 + NO2 + H20
    The water isn't needed, then you can easily balance...
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    (Original post by fayled)
    The water isn't needed, then you can easily balance...
    But mark scheme accepts either hydrogen or h2o
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    (Original post by otrivine)
    But mark scheme accepts either hydrogen or h2o
    How many marks is it worth?
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    (Original post by sapna09)
    Anyone have any tips on unstructured titrations?! Honestly can't do them and they are usually worth 7 marks! Thanks


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    I think apart from the obvious advice of practice lots of questions, I would recommend you just think, what do I definitely know? And build it up from there.

    Don't expect to always be able to just look at the question and know exactly what to do. Sometimes when it's unstructured, you just have a punt, you just use what you have been given. Then you work out what you can do next.

    Normally for example the first step is to work out the number of moles in the average titre they give you. Take it a step at a time then. You might be able to work out a ratio using an equation, and then go on from there.

    Got any specific questions you'd like help with?
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    (Original post by kitkat95)
    How many marks is it worth?
    1 mark
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    (Original post by otrivine)
    1 mark
    Well I got: 6HNO3 + S ---> H2SO4 + 6NO2 +2H2O
    I created two half equations: HNO3 + H+ + e ---> NO2 + H2O
    S + 4H2O ---> H2SO4 + 6H+ + 6e
    Then multiplied the HNO3 equation by 6:
    6HNO3 +6H+ + 6e ---> 6NO2 + 6H2O
    And combined the two equations. But that seems like waaay too much work to do for just one mark so not sure if this is right? I think the final answer is right but there must be a quicker way to do it.
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    (Original post by kitkat95)
    Well I got: 6HNO3 + S ---> H2SO4 + 6NO2 +2H2O
    I created two half equations: HNO3 + H+ + e ---> NO2 + H2O
    S + 4H2O ---> H2SO4 + 6H+ + 6e
    Then multiplied the HNO3 equation by 6:
    6HNO3 +6H+ + 6e ---> 6NO2 + 6H2O
    And combined the two equations. But that seems like waaay too much work to do for just one mark so not sure if this is right? I think the final answer is right but there must be a quicker way to do it.
    I know there is a method involving oxidation numbers but how
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    (Original post by otrivine)
    I know there is a method involving oxidation numbers but how
    The N in HNO3 has an oxidation number of 5 (oxygen is 2- and hydrogen 1+ so (3 x -2)+1= -5 so N=5). And the oxidation number of the N in NO2 is +4 because oxygen is 2- so 2 x -2 = -4 so to balance it out N must be +4.
    This means that the N has to gain an electron (be reduced) so:
    HNO3 + e --> NO2
    Then the oxygen atoms have to balance out so a H2O is added to the products: HNO3 + e ---> NO2 + H2O. Then the hydrogen atoms need to balance so a H+ is added o the reactants to get:
    HNO3 + H+ + e --> NO2 + H2O
    Then do the same process for the S.
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    i hate this exammmmmmmmmmmmmmmmmm
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    Ok, don't forget to finish them.
    Any chemistry genius can answer those questions?
    january 2013 paper F325
    Q1(v) - How to get Cr?
    Q6(a) - The mark schemes says enclosed container what do they mean by that?
    Q7(b)(ii) - How to get these equations?
    Q7(c)(ii) - How to do that?
    Q8(c)(ii) - How do we that?

    June 2012
    3(c)(ii) - How to do that?

    Jan 2011:
    7(a)(i) - How to get moles of O2

    June 2010:
    6(e) - How do I find C?
    7(b) - Why in the mark schemes they times the concentration of H2O2 by 34
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    anyone want to explain part 3e on Jan 11 ? I know its 2 marks but I just don't understand it
    Also with the dicarboxylate on the previous page how did you know the diagram? I haven't come across it figured its a circular as of the cyclo but just messed up the O groups -didn't realise there were 2 double bonds
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    Re-doing Past Papers is making me feel really good.

    Thanks again whoever uploaded that video on Titrations! I really just didn't understand the AS Theory Well Enough before but now I do!

    My Current Marks are (isolated under timed conditions - Funtry how do you get through the papers so fast - it still takes me about 1hr45)
    Specimen Paper: 86/100 (re-done - Thank you Funtry for Clearing up Errors)
    June 2010: 91/100 (re-done)
    Jan 2011: 86/100 (First time round, not re-doing)

    Then I've got June-11 to mark which I did yesterday

    Then today I'm re-doing Jan 12, Jun 12, and doing some Chem 4 and Physics 4/5 Prep!!!
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    (Original post by MedMed12)
    anyone want to explain part 3e on Jan 11 ? I know its 2 marks but I just don't understand it
    Also with the dicarboxylate on the previous page how did you know the diagram? I haven't come across it figured its a circular as of the cyclo but just messed up the O groups -didn't realise there were 2 double bonds

    Yes that was a nasty question, literally you have to apply your knowledge regarding the cis and trans platin, but instead of the simple NH3 and Cl , they want you to put a dicarboxylate ion
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    (Original post by otrivine)
    Yes that was a nasty question, literally you have to apply your knowledge regarding the cis and trans platin, but instead of the simple NH3 and Cl , they want you to put a dicarboxylate ion
    oh no I figured that I just meant I didnt know how to work out the structure of dicarboxylate so tried to intelligently guess (didnt know there were double bonds)
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    (Original post by Namod)
    Ok, don't forget to finish them.
    Any chemistry genius can answer those questions?
    january 2013 paper F325
    Q1(v) - How to get Cr?
    Q6(a) - The mark schemes says enclosed container what do they mean by that?
    Q7(b)(ii) - How to get these equations?
    Q7(c)(ii) - How to do that?
    Q8(c)(ii) - How do we that?

    June 2012
    3(c)(ii) - How to do that?

    Jan 2011:
    7(a)(i) - How to get moles of O2

    June 2010:
    6(e) - How do I find C?
    7(b) - Why in the mark schemes they times the concentration of H2O2 by 34
    For the first on your list, you are given the average mass of one atom. Now if you multiply this by the Avogadro constant you will get the average mass of one mole (i.e the molas mass). Then use the periodic table.

    For the second, the hydrogen gas has to be put in through a container otherwise it would escape. Like this:
    http://www.4college.co.uk/a/ss/cell6.gif
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    (Original post by MedMed12)
    oh no I figured that I just meant I didnt know how to work out the structure of dicarboxylate so tried to intelligently guess (didnt know there were double bonds)
    I think the structure would have been similar to the ethanoate ion?


    Who neg rep you?
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    (Original post by otrivine)
    I think the structure would have been similar to the ethanoate ion?


    Who neg rep you?
    hmm thats a true point! I guess it one of the A*/synoptic questions seeing as its only 2 marks but I because I got the structure wrong I wasn't sure if I'd lose the second mark when drawing it in replacement of cl- in the platin but I took it away just incase/

    I don't know meh nevermind
 
 
 
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