In a packed bed reactor, the concentration of a reactant A is described by the equation: [A] = [A]_0 e^(-kt), where [A] is the concentration of reactant A at time t, [A]_0 is the initial concentration of reactant A, t is time, and k is the reaction rate constant. If the initial concentration of reactant A is 2 mol/L and the concentration of reactant A is 1 mol/L after 5 minutes, determine the value of the reaction rate constant, k.