<s>[INST] Dehydrogenation of hydrocarbons is an important process in the petroleum industry and it takes place in the presence of catalysts. But such dehydrogenation cannot take place in a direct combustion reaction.
a) Explain why dehydrogenation of hydrocarbons doesn't occur in a combustion reaction.
b) The combustion fact sheet provides the value for n-pentane as -146.8 MJ/kg and the enthalpy of the reaction is -800 MJ/kg for this compound.
i) What is the percentage value of the fact sheet and the given value?[/INST]