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Homework Help: Calculate the oxidation number of carbon

  1. Jun 13, 2008 #1
    1. The problem statement, all variables and given/known data

    C6H12O6[tex]\rightarrow[/tex] 3CO2 + 3CH4 [tex]\Delta[/tex]H = -132 kJmol-1

    C6H12O6[tex]\rightarrow[/tex] 2CO2 + 2C2H5OH [tex]\Delta[/tex]H = -68 kJmol-1

    1. Calculate the oxidation number of carbon in each of the products of the first reaction.

    2. Comment on the relative advantages and disadvantages of these 2 types of fermentation as sources of fuel from glucose.

    2. Relevant equations

    3. The attempt at a solution

    1. i found carbon to be at an oxidation state of +4 in the products of the first reaction.

    2. the first reaction releases more energy than the second one. it is more exothermic.

    the second part contains 3 marks, so i think i need 2 more points, but i can't find anything more.

  2. jcsd
  3. Jun 15, 2008 #2
    Well I guess a disadvantage would be the production of CO2 everytime you break down glucose. So while it does release more energy it releases more CO2 as well.
  4. Jun 16, 2008 #3


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    Your first answer is incomplete. There are two products...

    In the first reaction, you have a mixture of two gases and you will have to separate them unless you want to use the methane contaminated with CO2. In the second reaction, the products are dissolved in the broth (beer?) and must be distilled to be purified. Which process do you think is easier?

    What advantage/disadvantage is there for a process that liberates more energy in the production of one of these fuels? Is that energy available for power production or is it wasted in the production of the fuel?
  5. Jun 17, 2008 #4
    i think that if the process producing the fuel liberates more energy, then on oxidation of the fuel, less energy will be liberated.

    and, i think it is easier to separate the methane from CO2 (maybe cooling the mixture to make the CO2 solidify?!) than taking the ethanol out of the broth.

    i had in mind that it was that energy released from the above reactions that were used, and not the energy from the further oxidation of methane or ethanol. :-S

    but what you say makes much more sense. thnks
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