(PhysChemBasics#10) In reversible reactions, the rates of the reverse and forward reaction are equal at equilibrium, the law of mass action can thus be derived kinetically. The energy profile tells us, that there is a simple relationship between activation energies and the enthalpy of reaction. With consecutive reactions and reactive intermediates, the steady state approximation applies: the concentration of the intermediate is approximately 0 and does not change with time. With parallel reactions, the reaction with the lower activation energy dominates - provided the reaction is kinetically controlled.