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G of CO2 per kWh from burning methane

  1. Jun 24, 2010 #1
    http://europe.theoildrum.com/node/6638" [Broken] has a chart that claims that the burning of methane yields 360 g of CO2 per kWh of energy released. I decided to check that, but I'm not getting the same answer they suggest. Here's what I did:

    CH4 + 2O2 = 2H2O + CO2
    -74.87 + 0= 2*-285.83 + -393.509
    = -571.66 + -393.509 +74.87= -890.229 kJ/mol

    (all standard enthalpies of formation came from wikipedia)

    CO2 is 44.011 g/mol
    890.229 kJ is 0.24728583333 kWh (significant figures be damned)

    44.011/0.24728583333 ≈ 178 g/kWh, as opposed to their 360 g/kWh

    I can't help but notice that my answer is suspiciously close to a factor of 2 off... but my eq. is balanced...
    Can someone tell me what I've done wrong?

    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Jun 24, 2010 #2
    You say per kWhr of heat, but their graph says per kWhr of electricity.
  4. Jun 24, 2010 #3
    *slaps forehead

    I figured I'd be kicking myself.
    Thanks, cesiumfrog.
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