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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 MacroniCheese)
    Good stuff! You should be good to go by next Wednesday
    Looool I hope so XD Won't stop me from worrying myself like crazy though hahaha
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    Hey guys, anybody got any tips on EXAM TECHNIQUE?? Im so sussed by it, I just cant seem to hack that understanding of what it is and how to master it whelp.
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    samb1234 Ayman! Can someone explain why the reaction on the right occurs by addition?

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    (Original post by keres)
    15 cm3 of a gaseous hydrocarbon requires 90 cm3 of oxygen for completecombustion, both volumes being measured at 15􀁱C and 1 atm. The formula of thehydrocarbon is

    A C4H6
    B C4H8
    C C4H10
    D impossible to calculate without knowing the molar volume of gases underthese conditions.

    Guys how do you do this? Please help
    (Original post by keres)
    15 cm3 of a gaseous hydrocarbon requires 90 cm3 of oxygen for completecombustion, both volumes being measured at 15􀁱C and 1 atm. The formula of thehydrocarbon is

    A C4H6
    B C4H8
    C C4H10
    D impossible to calculate without knowing the molar volume of gases underthese conditions.

    Guys how do you do this? Please help
    Anyone? :') x
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    (Original post by Don Pedro K.)
    samb1234 Ayman! Can someone explain why the reaction on the right occurs by addition?

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    It's because benzene needs to undergo substitution reactions because the delocalised ring of electrons needs to be maintained for stability - however with cyclohexa1-3 diene, there is no delocalised ring structure. it is comprised of 3 double bonds, and double bonds can undergo addition reactions.
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    (Original post by keres)
    It's because benzene needs to undergo substitution reactions because the delocalised ring of electrons needs to be maintained for stability - however with cyclohexa1-3 diene, there is no delocalised ring structure. it is comprised of 3 double bonds, and double bonds can undergo addition reactions.
    Ahhh of course! Thank you !
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    (Original post by keres)
    Anyone? :' x
    What's the answer for this?
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    (Original post by sabahshahed294)
    What's the answer for this?
    B x
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    (Original post by keres)
    B x
    I did it like this:-
    We have the volume of the hydrocarbon and oxygen given to us(gaseous volumes) so I used the equation, moles=volume/molar volume and found the moles of both the hydrocarbon and oxygen which had a ratio of 1:6. As this is a complete combustion, we know the products are gonna be Carbon Dioxide and Water. So, I just wrote the equation using the molar ratio I calculated:-

    CxHy + 6O2----> 4CO2+4H20.

    There are total 12 oxygen atoms so to balance them, I wrote 4 CO2 and 4H20.
    This means that carbon:hydrogen ratio is 1:2 hence 4:8 in this case which is why you get C4H8 as the answer(B)
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    (Original post by MacroniCheese)
    Good stuff! You should be good to go by next Wednesday
    You know you're on TSR when 'good to go' = 120 ums. xD
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    (Original post by Don Pedro K.)
    samb1234 Ayman! Can someone explain why the reaction on the right occurs by addition?

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    It's an alkene
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    Anyone know if anyone got anywhere with putting together an unofficial mark scheme?
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    Hey - what compound do diazonium ions decompose to when heated above 10oC? Was on a past paper but I've forgotten!
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    (Original post by gabby07)
    Hey - what compound do diazonium ions decompose to when heated above 10oC? Was on a past paper but I've forgotten!
    phenol
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    (Original post by samb1234)
    phenol
    Have you tried June 2013 (R)?
    • Thread Starter
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    (Original post by Don Pedro K.)
    Have you tried June 2013 (R)?
    not yet only done june 2013 so far
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    (Original post by samb1234)
    not yet only done june 2013 so far
    Okay haha
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    How come the answer is C here? I thought it'd be A as the electrodes are the same metals as those in solution?

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    (Original post by Peppercrunch)
    How come the answer is C here? I thought it'd be A as the electrodes are the same metals as those in solution?

    if you put iron you'd set up potential of Fe/Fe2+ and Fe/Fe3+
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    (Original post by Peppercrunch)
    How come the answer is C here? I thought it'd be A as the electrodes are the same metals as those in solution?

    If you look at the beaker on the right, you can see that the solution contains a mixture of FeSO4 (Fe2+ ions) and Fe2(SO4)3 (Fe3+) ions. Hence, there is no metal iron involved. The electrode is therefore made out of platinum, which is kind of the convention.
 
 
 
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