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Edexcel A2 Chemistry 6ch04/05 JUNE 2015 watch

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    (Original post by veniceswan)
    Can somebody please explain this question
    4.70=4.80+log(CH3COO-)
    -0.1=log(CH3COO-)
    e^-0.1=(CH3COO-)
    0.9048={CH3COO-}
    then I found the moles and mass, but the mark scheme says {CH3COO-}=0.794
    Please can somebody correct me
    Attachment 424309
    conc of acid- 1 (from question)
    H+ conc- 10^-4.7
    Ka- 1.7x10-5
    sub all of this values into Ka expression and arrange to get the conc of the salt to be 0.8520...
    moles of salt- 0.8520..x500/1000=0.42600...
    mass of salt- 0.42600...x82= 34.9g
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    (Original post by MoHoosen9167)
    You'd lose marks for not showing that you're inputting a concentration, even if it is say for instance 075/v in your Kc expression. Also, the units may cancel out, but they may not in which case you need to show you're inputting concentration units (moldm-3)
    Alright so if they haven't given me a volume, I put it over V in the Kc expression?
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    Can anyone remember which paper that massive 7-marker NMR Question was in??
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    (Original post by frozo123)
    Alright so if they haven't given me a volume, I put it over V in the Kc expression?
    Yup!
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    (Original post by mohoosen9167)
    if your reactants and products have an "aq" state symbol (apart from water, obv) then you exclude water from the kc calculation. If water is being formed, say for instance in esterification (assuming you're using dry reagents), then you include water in the kc calculation. Hope that's helped!

    Reflux: http://what-when-how.com/wp-content/...703_thumb1.png

    and distilling: http://upload.wikimedia.org/wikipedi...aratus.svg.png
    thank you knew i could always count on you

    Edit: was meant to be all caps but ok then tsr
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    (Original post by MoHoosen9167)
    Yup!
    alrightt, hopefully there's quite a bit of acid/base chemistry
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    (Original post by ArielHaeems)
    I'd draw an electric heater rather than a bunsen burner for each of them, don't think it matters though. Also, determining when H2O is the solvent, I'm not exactly sure
    thank you!!
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    (Original post by MoHoosen9167)
    If your reactants and products have an "aq" state symbol (apart from water, obv) then you exclude water from the Kc calculation. If water is being formed, say for instance in esterification (assuming you're using dry reagents), then you include water in the Kc calculation. Hope that's helped!

    Reflux: http://what-when-how.com/wp-content/...703_thumb1.png

    and Distilling: http://upload.wikimedia.org/wikipedi...aratus.svg.png
    Hang on, stupid Q. Is water only excluded when it is in reactant? What if all is aq and it is formed? Still excluded?

    And also same for Kp? or not? confused now lol
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    (Original post by Nautic4l)
    Can anyone remember which paper that massive 7-marker NMR Question was in??
    there is a 6 marker in jan 2010 and 5 marker in jan 2015
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    (Original post by frozo123)
    alrightt, hopefully there's quite a bit of acid/base chemistry
    Kc and Kp calculations only
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    (Original post by MoHoosen9167)
    Kc and Kp calculations only
    lol I don't like the section C ones
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    (Original post by Maham88)
    there is a 6 marker in jan 2010 and 5 marker in jan 2015
    Noo there's a 7-marker but in papers after Jan 11? anyoneeee?
    I closed my tab ffs lol
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    http://qualifications.pearson.com/co...e_20100127.pdf

    Okay so if someone can explain 26b I would be so so grateful.

    For X, I know the hextet is next to CH5, singlet adj to C with no H, quintet next to CH4 and so on and same for Y

    My question is HOW ON EARTH do I put it all together? If you could explain in steps that'd be great

    Thank you
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    (Original post by Nautic4l)
    Hang on, stupid Q. Is water only excluded when it is in reactant? What if all is aq and it is formed? Still excluded?

    And also same for Kp? or not? confused now lol
    If water is a reactant, but not a solvent, then it has to appear.

    CH3COOCH2CH3(l) + H2O(l) ---> CH3CH2COOH(l) + CH3CH2OH(l)

    If water is gaseous (either produced as steam or in Kp) then it has to appear.

    CH4(g) + H2O(g) ---> CO(g) + 3H2(g)

    If water is a reactant or product, but also the solvent, then it does not appear.

    Cr2O7(2-) (aq) + H2O(l) ---> 2CrO4(2-) (aq) + 2H+(aq)

    Edit: Wrong species on the RHS of the final equation whoops.
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    (Original post by MoHoosen9167)
    If water is a reactant, but not a solvent, then it has to appear.

    CH3COOCH2CH3(l) + H2O(l) ---> CH3CH2COOH(l) + CH3CH2OH(l)

    If water is gaseous (either produced as steam or in Kp) then it has to appear.

    CH4(g) + H2O(g) ---> CO(g) + 3H2(g)

    If water is a reactant or product, but also the solvent, then it does not appear.

    Cr2O7(2-) (aq) + H2O(l) ---> 2Cr2O7(2-) (aq) + 2H+(aq)
    Perfect thank you. Can you help me with the NMR question I linked please? lol
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    (Original post by Nautic4l)
    Perfect thank you. Can you help me with the NMR question I linked please? lol
    Having a go of it now!
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    (Original post by Nautic4l)
    Perfect thank you. Can you help me with the NMR question I linked please? lol
    I've edited the final equation because the Dichromate on the RHS should be a Chromate!
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    (Original post by MoHoosen9167)
    Having a go of it now!
    Thank you so much
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    Good luck everyone!


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    (Original post by Nautic4l)
    Can anyone remember which paper that massive 7-marker NMR Question was in??

    Jan 2013 last question
 
 
 
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