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Assign oxidation numbers to each atom in the following combustion reactions and then tell which combustion reaction is?

is most efficient and which combustion reaction is least efficient:

C8 H18 + 17/2 O2 ⇨ 8 CO + 9 H2O

C8 H18 + 9/2 O2 ⇨ 8 C + 9 H2O

C8 H18 + 25/2 O2 ⇨ 8 CO2 + 9 H2O

1 Answer

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  • 2 years ago

    ___________________C8 H18 + (17/2) O2 → 8 CO + 9 H2O

    Oxidation number: __-2.25 +1 ________ 0 ___ +2 -2 __ +1 -2

    ___________________C8 H18 + (9/2) O2 → 8 C + 9 H2O

    Oxidation number: __-2.25 +1 _______ 0 ____ 0 ___ +1 -2

    __________________C8 H18 + (25/2) O2 → 8 CO2 + 9 H2O

    Oxidation number: _-2.25 +1 ________ 0 ____+4 -2 __ +1 -2

    The third reaction is the most efficient because the increase in oxidation number of C is the greatest (from -2.25 to +4).

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