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

[xdrgnh]

Homework Statement

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.

Homework Equations

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

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.

 

[phyzguy]

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?