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Chemistry Marking Scheme help

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  • 29-08-2014 7:35pm
    #1
    WoolyAbyss
    Registered Users Posts: 98 ✭✭


    I just came back from viewing my script and I think I could have gotten more marks on question 6.

    http://www.examinations.ie/archive/markingschemes/2014/LC022ALP000EV.pdf
    (Page 15)

    I used the incorrect alkane C3H8

    it says if you use an incorrect alkane CnH(2n+2) allow 3 for nC correctly burned.

    I wrote

    3C + 3O2 > 3CO2 DeltaH = -1180.5 KJ

    Should I have gotten the marks for this?


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    #2
    rainbowtrout
    Registered Users Posts: 15,381 ✭✭✭✭rainbowtrout


    WoolyAbyss wrote: »
    I just came back from viewing my script and I think I could have gotten more marks on question 6.

    http://www.examinations.ie/archive/markingschemes/2014/LC022ALP000EV.pdf
    (Page 15)

    I used the incorrect alkane C3H8

    it says if you use an incorrect alkane CnH(2n+2) allow 3 for nC correctly burned.

    I wrote

    3C + 3O2 > 3CO2 DeltaH = -1180.5 KJ

    Should I have gotten the marks for this?

    No.

    They are referring to the third line of the simultaneous equation:

    C4H10 → 4C + 5H2 ΔH = 125.7 kJ

    where nC refers to the number of carbons and (n+1)H2 is the number of hydrogens produced from the alkane.


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