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Alkanes and combustion

Hi,

Why is it that saturated hydrocarbon which have longer carbon chain lengths do not combust as easily as those with shorter chain lengths.
And secondly, why is it that the longer the carbon chain length the more energy that is released on combustion?

Thanks!
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moshe015
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Original post by SANTR
Hi,

Why is it that saturated hydrocarbon which have longer carbon chain lengths do not combust as easily as those with shorter chain lengths.
And secondly, why is it that the longer the carbon chain length the more energy that is released on combustion?

Thanks!


Id imagine its because combustion requires breaking the van de waal forces between the chains. Longer chains can lie closer together and have more electrons so more van de waal forces so they require more energy to be broken, therefore they don't combust as easily.

Im guessing that since combustion of fuels release energy

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Original post by SANTR
Hi,

Why is it that saturated hydrocarbon which have longer carbon chain lengths do not combust as easily as those with shorter chain lengths.
And secondly, why is it that the longer the carbon chain length the more energy that is released on combustion?

Thanks!

Hi I`m not sure but;

-For the first question I think more energy is needed to break the numerous C-C and C-H bonds thus an increased demand for oxygen but on combustion data analysis it can be noted that 1 mole of a hydrocarbon requires (for alkane :x+y/4)moles of oxygen.
-For the second I think more energy is produced because when we are to compare the bond energies of a long chained hydrocarbon to those of a short chained hydrocarbon there are many(for a long chained hydrocarbon than a short chained) C-C bonds thus an increase in the amount of energy produced.

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