Fundamentally, what drives mass transfer of oxygen and fuel in simple combustion?

Question

Quizplus · Accepted Answer

Concentration gradients drive mass transfer of oxygen and fuel in simple combustion. This is because the reactants (i.e. oxygen and fuel) are typically present in higher concentrations in the surroundings compared to the combustion zone, where they are consumed. As a result, the reactants diffuse from the surroundings towards the combustion zone, leading to mass transfer of oxygen and fuel.

Fundamentally, What Drives Mass Transfer of Oxygen and Fuel in Simple