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Edexcel A2 Chemistry Exams -6CH04 (14th June) and 6CH05 (22nd June) Discussion Thread Watch

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    (Original post by Rahatara Sadique)
    Hi, would appreciate if anyone helps me in this question.

    10 cm3 of a gaseous hydrocarbon was mixed with excess oxygen and ignited. The gas volumes were measured at room temperature and pressure before and after combustion and it was found that the total gas volume contracted by 20 cm3. Given that combustion was complete, the formula of the hydrocarbon was:

    A C4H4
    B C4H6
    C C4H8
    D C4H10 The answer is A
    Everyone's fav MCQ
    20cm3 contracted because water condensed as it was carried out at room temp
    10cm3 of the hydrocarbon therefore produced 20cm3 of water. Water has 2 H atoms per molecule so from the hydrocarbon : water ratio you know that a mole of the hydrocarbon produces two moles of water, which means a mole of the hydrocarbon has four moles of H atoms.
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    (Original post by C0balt)
    Yeah I wondered too when I did that paper. I got the right answer without 10*40 thing iirc though. Which paper was this?
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    It's the June 2014 paper - q 21
    I keep on getting 0.293 rather than 0.0293 for the concentration
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    (Original post by C0balt)
    I love how this thread is so populated now that it's the night before the exam
    Yeah but experience it while we can , since most of us will be going to Uni in September/October (hopefully no one needs to resit the year since there will be the new spec to learn).

    Gotta lov' a propah communi'y work'n togeVa.
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    (Original post by Wunderbarr)
    Perhaps it may be better to say all zwitterions have a pH of 7, due to the overall neutral charge?

    And then alanine at pH 7 should just be its zwitterion? That would be my "guess" (unfortunately it's just that).
    Ah okay haha thanks anyways

    Lol I just marked my paper...Got 57/90...Let's check the grade boundaries...

    LOL I was only 4 marks off an A...that paper was crazy. If ours is like that tomorrow...gg.
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    (Original post by C0balt)
    Yeah I wondered too when I did that paper. I got the right answer without 10*40 thing iirc though. Which paper was this?
    x 10 is to find the moles in 250 and x 40 is the volume ( divide by 25/1000 is same as multiplying by 40)
    I think
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    got 2 hours to learn copper and chromium chemistry... should i take a 50/50 risk and learn one really well or learn both less well? anyone have any predictions on whether it will come up or which one will come up?
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    (Original post by Wunderbarr)
    Yeah but experience it while we can , since most of us will be going to Uni in September/October (hopefully no one needs to resit the year since there will be the new spec to learn).

    Gotta lov' a propah communi'y work'n togeVa.
    oh god won't there be a legacy paper?
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    (Original post by Don Pedro K.)
    June 14 :/ I did crap in this one lol...



    Ahhh okay thanks !
    (Original post by the-anonymous-me)
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    It's the June 2014 paper - q 21
    I keep on getting 0.293 rather than 0.0293 for the concentration
    Well I really have no idea what the 40 is about but what I did is

    3.99*10^-3*3/2=5.98*10^-3
    5.98*10^-3*10=0.0598
    0.0598/(25/1000)=2.39
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    (Original post by ramadeen)
    x 10 is to find the moles in 250 and x 40 is the volume ( divide by 25/1000 is same as multiplying by 40)
    I think
    Oh my God that makes sense, so that's basically what I did but Edexcel being so vague lmao
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    (Original post by C0balt)
    Well I really have no idea what the 40 is about but what I did is

    3.99*10^-3*3/2=5.98*10^-3
    5.98*10^-3*10=0.0598
    0.0598/(25/1000)=2.39
    See what I don't get is, why do we need to multiply by 10 if Q and the sample of R's volumes are 25cm^3 anyway?

    Btw what mark did you get in this paper?

    (Original post by ramadeen)
    x 10 is to find the moles in 250 and x 40 is the volume ( divide by 25/1000 is same as multiplying by 40)
    I think
    Ah that makes sense haha
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    Why did I think it was acceptable to learn the whole of Chemistry unit 5, the night before the exam... Idk but I am screwed.
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    (Original post by C0balt)
    Oh my God that makes sense, so that's basically what I did but Edexcel being so vague lmao
    same, i didn't do it like that. who does x 40 anyways lol
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    [QUOTE=Don Pedro K.;65992405]See what I don't get is, why do we need to multiply by 10 if Q and the sample of R's volumes are 25cm^3 anyway?

    Btw what mark did you get in this paper?

    i got 70 on that paper, i've done some of the questions before though. I don't know what to do now, i wanna do another paper but also i wanna revise some things i don't remember I'M PANICKING
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    (Original post by Don Pedro K.)
    See what I don't get is, why do we need to multiply by 10 if Q and the sample of R's volumes are 25cm^3 anyway?

    Btw what mark did you get in this paper?



    Ah that makes sense haha
    (Original post by C0balt)
    Well I really have no idea what the 40 is about but what I did is

    3.99*10^-3*3/2=5.98*10^-3
    5.98*10^-3*10=0.0598
    0.0598/(25/1000)=2.39
    The answer isn't 2.39 though

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    [QUOTE=ramadeen;65992531]
    (Original post by Don Pedro K.)
    See what I don't get is, why do we need to multiply by 10 if Q and the sample of R's volumes are 25cm^3 anyway?

    Btw what mark did you get in this paper?

    i got 70 on that paper, i've done some of the questions before though. I don't know what to do now, i wanna do another paper but also i wanna revise some things i don't remember I'M PANICKING
    Wow nice one!
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    How many past papers do you people do? Ive done maybe 6/7.... hope its enough....for a challenge I'd recommend june 2014 the original paper that got replaced.
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    (Original post by Don Pedro K.)
    See what I don't get is, why do we need to multiply by 10 if Q and the sample of R's volumes are 25cm^3 anyway?

    Btw what mark did you get in this paper?



    Ah that makes sense haha
    Got 78, that paper was difficult.
    Original was 25 but was then diluted to 250cm3. The 25 used for titration was therefore also the diluted version (10 times more dilute than original).
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    (Original post by the-anonymous-me)
    The answer isn't 2.39 though

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    Uh it appears to be 2.39 to my eyes?
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    (Original post by C0balt)
    Got 78, that paper was difficult.
    Original was 25 but was then diluted to 250cm3. The 25 used for titration was therefore also the diluted version (10 times more dilute than original).
    what the heck o.O 78....on that evil paper? You're sorted lol.
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    (Original post by Supermanxxxxxx)
    Attachment 554519
    I can't figure any of these out


    Posted from TSR Mobile
    For the first part you know that 36.82% of TO2 is Oxygen. Therefore 32 must be 36.82% of the total RFM. So you can do 32/0.3682 to calculate the Total RFM = 84.9. Then it's a simple subtraction 84.9 - 32 = RFM of T. You get 54.9 which is Manganese!
 
 
 
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