Lower heat of combustion=more stable

[swindoll]

Could someone explain why this is true? Doesn't make sense in my head...

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[TheEpicFruitCake]

hmm I can see how it would make sense. This is just a guess, but more stable molecules have less energy in them.

 

[swindoll]

That's correct, but how does that relate to heat of combustion? I thought that heat of combustion is the amount of heat that needs to be ADDED in order for the combustion to occur... But then I also remember that combustion is a spontaneous process.. Ahh so confused!

 

[TheEpicFruitCake]

it is usually the amount of heat released. The actual experiment is done in a bomb calorimeter.

Literally all they do is have an isolated system (the calorimeter). They have water as well and they set whatever they want on fire. The change in temp of the water tells us how much energy was released (q). We know this because we know the specific heat of water. Hess's law when I googled it.