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Carbon dioxide output?

  1. Aug 23, 2007 #1
    Carbon dioxide output??

    How would you go about calculating the carbon dioxide output per unit mass and volume for combustion products, i have already calculated the energy outputs per unit mass and volume.

    Many thanks.
     
  2. jcsd
  3. Aug 24, 2007 #2

    Gokul43201

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    Pick an example and show us what you would try.
     
  4. Aug 24, 2007 #3
    for eg. combustion of CH4:
    CH4(g) + 2O2(g) ---> CO2(g) + 2H2O(l)

    enthalpy of combustion: (-393.51) + 2(-241.82) - (-74.81) = -802.34 kj/mol

    energy output per unit mass:
    802.34 x 1000/16(molar mass) = -50146.25 kj/kg

    energy output per unit volume:
    -50146.25 x 0.645(mass density) = -32344.33 kj/m3

    However I have no clue on how to calculate the carbon dioxide output per unit mass and volume, any help would be kindly appreciated.
    Many thanks.
     
  5. Aug 24, 2007 #4

    Gokul43201

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    From the balanced equation, 1 mole of CH4 makes 1 mole of CO2. How much does a mole of CH4 weigh? What about a mole of CO2? And, at STP, what volume does a mole of (ideal) gas occupy.
     
  6. Aug 24, 2007 #5
    1 mole of CO2= 44g
    1 mole of CH4= 16g
    At STP the volume of an ideal gas occupies 0.0224 m3...
     
  7. Aug 24, 2007 #6
    for eg. combustion of CH4:
    CH4(g) + 2O2(g) ---> CO2(g) + 2H2O(l)

    enthalpy of combustion: (-393.51) + 2(-241.82) - (-74.81) = -802.34 kj/mol

    energy output per unit mass:
    802.34 x 1000/16(molar mass) = -50146.25 kj/kg

    energy output per unit volume:
    -50146.25 x 0.645(mass density) = -32344.33 kj/m3

    1 mole of CO2= 44g
    1 mole of CH4= 16g
    At STP the volume of an ideal gas occupies 0.0224 m3...

    the CO2 energy output per mass....
    -802.34 kj/mol divided by 12 g/mol equals 66.86 kj/g

    am i doing the right thing, and how would you calculate the CO2 output per unit volume?

    Many thanks.
     
  8. Aug 24, 2007 #7
    -802.34 kj/mol divided by 12 g/mol equals 66.86 kj/g
    CORRECTION: DIVIDED BY 16G/MOL
     
  9. Aug 25, 2007 #8

    Gokul43201

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    So, the CO2 output (assuming stoichiometric conditions) is:
    44g of CO2 per mole of CH4
    OR
    2.75g of CO2 per g of CH4
    OR
    1 liter of CO2 per liter of CH4...etc.
     
  10. Aug 25, 2007 #9
    however i need to work out the CO2 output per unit mass and volume,
    the units would be kj/kg and kj/m3,correct?

    the CO2 energy output per mass....
    -802.34 kj/mol divided by 12 g/mol equals 66860 kj/kg

    the CO2 energy output per unit volume:
    66860 x 0.645 (CH4 mass density)= 43124.7 kj/m3

    Have i done these calculations properly?
    Thanks.
     
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