According to WolframAlpha, the change in enthalphy in the combustion of propane is -2220 kJ/mol. How do I calculate the activation energy required start the reaction in the first place? Do you use the same principles as when calculating delta H or am I missing something mind bogglingly obvious?
The autoignition temperature is an external variable. It depends upon total pressure and oxygen partial pressure. For paper it is famously 232.778 C (significant figures aside).