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OCR A2 CHEMISTRY F324 and F325- 14th and 22nd June 2016- OFFICIAL THREAD watch

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    (Original post by ReeceM1)
    Most of the time it says ignore Ref to Concentration on the mark scheme. Although I have seen times where it says conc but I'm not sure I've ever seen dilute?

    So when it asks for reagents I just put concentrated and either way it'll normally be right.
    Well you would have to put dilute acid/alkali for the hydrolysis of esters.

    (Original post by tcameron)
    Most of the time they ignore it
    I've only seen when it's required for esters and for the reduction of nitrobenzene - pretty sure you must state concentrated H2SO4 and concentrated HCl for those ones
    Thanks for that, I might as well try and remember the exact conditions for each reaction, just in case.
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    I've worked out the precipitate is Fe(OH)3 but could someone explain how to calculate the gas from density PLEASE
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    (Original post by AqsaMx)
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    I've worked out the precipitate is Fe(OH)3 but could someone explain how to calculate the gas from density PLEASE
    I assume you mean the next question?
    Think about the equation to find the volume of a gas: n=v/24,000 cm3
    Assume 1cm3 = 1=333x10^-3 g
    So that means 24,000cm3 = 1.333x10^-3 x 24,000
    That equals 31.992 gmol^-1
    On the periodic table the molecular mass closet to this value must be O2 (oxygen) which is 32gmol^-1
    So the gas is O2
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    (Original post by tcameron)
    I assume you mean the next question?
    Think about the equation to find the volume of a gas: n=v/24,000 cm3
    Assume 1cm3 = 1=333x10^-3 g
    So that means 24,000cm3 = 1.333x10^-3 x 24,000
    That equals 31.992 gmol^-1
    On the periodic table the molecular mass closet to this value must be O2 (oxygen) which is 32gmol^-1
    So the gas is O2
    But how do we know 1cm3 = 1.333x10-3 and why are you multiplying volume by 24?
    Sorry, I'm really confused
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    Also with the ligand substitution reaction of Cu(H2O)62+ + 4Cl- > [CuCl4]2- + 6H2O

    Why might we observe the formation of a colour other than yellow?
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    (Original post by AqsaMx)
    Also with the ligand substitution reaction of Cu(H2O)62+ + 4Cl- > [CuCl4]2- + 6H2O

    Why might we observe the formation of a colour other than yellow?
    I think it's because the system is in equilibrium and therefore the solution is a mix of the hexaaqua ion (blue) and the tetrachloro ion (yellow) which makes the solution appear a green colour.
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    Oh makes sense! Thank you 😊
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    Could anyone help me with this problem? Sorry for the scruffy writing, but I was trying to include the equations which apply to the problem also, thank you
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    (Original post by AqsaMx)
    But how do we know 1cm3 = 1.333x10-3 and why are you multiplying volume by 24?
    Sorry, I'm really confused
    To find the volume of a gas it occupies 24dm3
    The volume of the gas had density so if a question is about the density of a gas it'll always involve the 24dm3/24000cm3 - just something to remember really, especially since the question said it was measured at room temperature and pressure is a indication of that.
    I can't really explain it well but I think it was that, 1cm3 is the same as gcm-3 of a gas so you make that equal the density then multiple it by 24000
    If it was in gdm-3 then you make it equal to 1dm3 and multiply the density by 24
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    I know VO2 needs to react with something to reform the catalyst, but could anyone help me with what it needs to react with?
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    (Original post by AqsaMx)
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    I know VO2 needs to react with something to reform the catalyst, but could anyone help me with what it needs to react with?
    Second Step: 2VO2 + 0.5O2 --> V2O5
    This cancels the 2VO2 formed in first step, reforms the catalyst and adds the 0.5O2 to form the overall equation,
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    (Original post by Sahil_)
    Second Step: 2VO2 + 0.5O2 --> V2O5
    This cancels the 2VO2 formed in first step, reforms the catalyst and adds the 0.5O2 to form the overall equation,
    But aren't you supposed to form H2SO4 to form the product?
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    Attachment 527681527683
    Hard, redox mole question!!
    Serious help needed guys!
    Attached Images
      
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    (Original post by AqsaMx)
    But aren't you supposed to form H2SO4 to form the product?
    No, SO3 is the product, you are trying to get to the overall equation stated in the question.
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    (Original post by AqsaMx)
    Attachment 527681527683
    Hard, redox mole question!!
    Serious help needed guys!
    Is the answer to part b 2:1 ??


    Posted from TSR Mobile
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    (Original post by AqsaMx)


    Could anyone help me with this problem? Sorry for the scruffy writing, but I was trying to include the equations which apply to the problem also, thank you

    My attempt to your question. Answer ended up to be 40.2 and I assumed X to be calcium.
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    (Original post by suibster)

    My attempt to your question. Answer ended up to be 40.2 and I assumed X to be calcium.
    Thank you so much
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    Could anyone explain (c) (d) and (e)
    And in general explain his fuel cells work.
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    (Original post by Saywhatyoumean)
    Is the answer to part b 2:1 ??


    Posted from TSR Mobile
    Yes it is, I finally worked it out
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    I have a qualitative on identifying transition metals through their reactions
    Could anyone possibly give me advice for it ?
 
 
 
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