Why Activation energy for Hydrogen burning is extremely high?
Answers
My teacher posed this question in class and it stumped me, primarily based on my lack of fundamentals of thermodynamics: Peter Griffin was sitting around when all of a sudden he spontaneously combusts (Based on an episode). Is this possible and if not, under what circumstances is this possible?
My reasoning is
Peter+O2→H2O+CO2
There are more gas particles so entropy must increase, ΔH is negative since it is a combustion reaction and so according to
ΔG=ΔH−TΔS
Meaning free energy decreases... Which doesn't seem to make sense because it's highly unlikely that humans spontaneously combust. This got me thinking that the reaction itself is spontaneous. It just does not proceed because it cannot start the reaction due to insufficient activation energy (Particles not travelling fast enough).
My teacher said ΔH is positive which makes no sense to me... In a combustion reaction energy is released. He said it only occurs at very high temperatures because TΔS is large enough to counter the positive ΔH.
Is my teacher right or is my reasoning more correct?