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Homework Help: How long will the sun burn if only combustion is happening.

  1. Feb 3, 2014 #1
    1. The problem statement, all variables and given/known data
    The sun has a mass of 2*10^30kg and gives off energy at a rate of 3.9*10^26 watts. If the source of the sun's energy energy were ordinary combustion of methane how long will it last.

    2. Relevant equations

    delta Enthalpy of the combustion of methane is -802 kj. Energy equals watts times time.

    3. The attempt at a solution

    All I need to know is this. When I do this problem do I use the mass of both the methane and 2O_2 which is 80 grams per mole or just the methane which is 16 grams per mole. I did this problem using 80 grams per mole because that's the mass of the fuel that is burning that gives off 802 kj of energy.
  2. jcsd
  3. Feb 3, 2014 #2


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    Science Advisor

    Well, it seems like to do it right you need to include the mass of both combustion products. You can't burn the methane without oxygen, right?
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