Arrhenius Equation
Definition
Mathematical expression relating reaction rate to temperature: k = A × exp(-Ea/RT). The exponential dependence explains the self-accelerating nature of combustion as temperature rises.
- Formula
- k = A x exp(-Ea/RT)
- Relates
- Reaction rate to temperature
- Key variable
- Ea, activation energy
- Forensic relevance
- Explains self-accelerating combustion
Common questions
How does the Arrhenius equation explain fire growth becoming self-accelerating?+
Because rate depends exponentially, not linearly, on temperature, a small rise in temperature produces a disproportionately large increase in reaction rate, so as combustion releases heat and raises local temperature further, the reaction rate climbs faster and faster until other limits such as fuel or oxygen availability intervene.
What does activation energy represent physically in a combustion reaction?+
It is the minimum energy barrier that reactant molecules must overcome before they can react, so fuels with a lower activation energy ignite and sustain combustion more readily at a given temperature than fuels requiring more energy input to start reacting.
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