The thermodynamics of two chemical systems obeying Arrhenius law kinetics are studied from the viewpoint of finite time thermodynamics. The first is the determination of the maximum thermodynamic or chemical efficiency of a synthetic process whose heat input appears as preheating to overcome an activation barrier. The second is the determination of maximum power that can be obtained from an exothermic reaction carried out in a continuous flowsystem. The maximum power, achieved with a finite, nonzero flow rate, is a sensitive function of the activation energy of the reaction.