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Thread: Is combustion endothermic, too?

  1. #1 Is combustion endothermic, too? 
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    Aside from being exothermic, is it also considered "semi-endothermic" because combustion requires some form of heat for it to start?


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  3. #2  
    Anti-Crank AlexG's Avatar
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    Combustion can be started chemically, with no additional heat required.


    Its the way nature is!
    If you dont like it, go somewhere else....
    To another universe, where the rules are simpler
    Philosophically more pleasing, more psychologically easy
    Prof Richard Feynman (1979) .....

    Das ist nicht nur nicht richtig, es ist nicht einmal falsch!"
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  4. #3  
    Bullshit Intolerant PhDemon's Avatar
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    Whether a reaction is endothermic or exothermic is a thermodynamic definition, i.e. is the energy of the reactants higher/lower than the products. Needing energy input to start the reaction is due to an activation energy ( a kinetic phenomenon) and irrelevant to the definition of a reaction as endothermic or exothermic.
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  5. #4  
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    Ah right thanks.
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  6. #5  
    Bullshit Intolerant PhDemon's Avatar
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    No problem, a lot of things in chemistry come down to kinetics or thermodynamics and although both have an influence on whether a reaction occurs or not, they are often considered separately. Thermo tells you whether a reaction results in an entropy increase (and therefore whether it is energetically favourable or not), kinetics tells you about the rate it will occur at (some energetically favourable reactions occur so slowly they effectively don't happen).
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  7. #6  
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    I'm trying to "like" your comment but I can't. Still, thanks again.
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  8. #7  
    Bullshit Intolerant PhDemon's Avatar
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    Yeah, the "likes" seem to be down at the minute...
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