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    (Original post by popo111)
    What about if your teachers refuse to give it to you yet and you have completed all past papers?
    Shank them fam
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    (Original post by drandy76)
    Carbonate ion is composed of two elements


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    So does that mean you have to work out the lattice enthalpy for the carbonate ion first?
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    Can anyone explain the last question on the Jan 2012 f325 paper please!!
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    Can anyone explain the last question on the Jan 2012 f325 paper please!!
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    (Original post by AqsaMx)
    Can anyone explain the last question on the Jan 2012 f325 paper please!!
    Electrode potential for potassium manganate is more positive than in chlorine, so the manganate ions will react with chlorine. The electrode potential in potassium dichromate is more negative than chlorine. Look at the information on page 20.
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    (Original post by rory58824)
    Electrode potential for potassium manganate is more positive than in chlorine, so the manganate ions will react with chlorine. The electrode potential in potassium dichromate is more negative than chlorine. Look at the information on page 20.
    But it says the titration is done between Cr2O7 and Fe2+ so I thought you would say MnO4- has a more positive electrode potential than Fe? I don't get why it mentions Cl
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    Using the redox systems in Table.1 construct an equation for a reaction between acidified dichromate and CHOOH

    But the table has two CHOOH, how do you know which one to choose? Name:  image.jpg
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    (Original post by AqsaMx)
    But it says the titration is done between Cr2O7 and Fe2+ so I thought you would say MnO4- has a more positive electrode potential than Fe? I don't get why it mentions Cl
    Excess HCl is used (stage 1), so as a result MnO4- would react with the chloride ions.
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    Why does the equation here have to involve OH- ions??
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    (Original post by rory58824)
    Excess HCl is used (stage 1), so as a result MnO4- would react with the chloride ions.
    Thank you so much
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    (Original post by AqsaMx)
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    Why does the equation here have to involve OH- ions??
    It probably says somewhere in the stem of the question something to do with the reaction occurring in alkaline conditions/resulting in an alkaline solution. Edit: and the hydroxide ions are included to balance the equation.

    But your answer to the question above is not correct by the way. Equilibrium does shift to the RHS but that is because carbon dioxide reacts with water to produce carbonic acid. The carbonic acid reacts with the hydroxide ions therefore decreases the concentration of hydroxide so equilibrium shifts to the right to counteract the change.
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    (Original post by AqsaMx)
    Using the redox systems in Table.1 construct an equation for a reaction between acidified dichromate and CHOOH

    But the table has two CHOOH, how do you know which one to choose? Name:  image.jpg
Views: 146
Size:  238.7 KB
    It says reaction between CHOOH and acidified dichromate, meaning:

    Acidified dichromate + HCOOH..

    how do we get that? Well using the anticlockwise rule, we need the hcooh to be on the right hand side of the equation so use the first equation with hcooh
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    How is everyone feeling about the two exams?? After last years papers, I reckon f324 will be slightly easier and f325 marginally harder
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    (Original post by ReeceM1)
    It probably says somewhere in the stem of the question something to do with the reaction occurring in alkaline conditions/resulting in an alkaline solution. Edit: and the hydroxide ions are included to balance the equation.

    But your answer to the question above is not correct by the way. Equilibrium does shift to the RHS but that is because carbon dioxide reacts with water to produce carbonic acid. The carbonic acid reacts with the hydroxide ions therefore decreases the concentration of hydroxide so equilibrium shifts to the right to counteract the change.
    Yeah I know, these questions were answered months ago when I didn't know the content well
    Thank you
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    (Original post by zirak46)
    It says reaction between CHOOH and acidified dichromate, meaning:

    Acidified dichromate + HCOOH..

    how do we get that? Well using the anticlockwise rule, we need the hcooh to be on the right hand side of the equation so use the first equation with hcooh
    Thank you so much
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    (Original post by Heisenberg___)
    How is everyone feeling about the two exams?? After last years papers, I reckon f324 will be slightly easier and f325 marginally harder
    Oh great. Pls f325 dont be hard.
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    Fingers crossed OCR gives us 2 easy papers as they're probably focusing on their new spec.
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    (Original post by rory58824)
    Fingers crossed OCR gives us 2 easy papers as they're probably focusing on their new spec.
    I believe papers are made some years in advance....

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    There was a question on electrode potentials in a paper. I can't remember it exactly but it said in alkaline conditions OH- reacted with H+ shifting equilibrium to the other side because the removal of H+ ions made the electrode potential more negative?
    Does anyone know why this is or is it just something we should know?
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    (Original post by AqsaMx)
    There was a question on electrode potentials in a paper. I can't remember it exactly but it said in alkaline conditions OH- reacted with H+ shifting equilibrium to the other side because the removal of H+ ions made the electrode potential more negative?
    Does anyone know why this is or is it just something we should know?
    I think its if H+ was in the product side of equilibrium and the concentration of it is decreased, the equilibirium will shift to the left to conpensate and reduce EP doing so.
    If H+ was on right and it decreased in concentration, the EP will increase
 
 
 
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