When the reaction is dependent on one reactant... The rate constant is the slope when the change in inverse concentration (1/[A]) is graphed over time When the reaction is dependent on two reactants... You graph the change in the ln([A]\\[B]) over time, where A and B are the reactants The slope is equal to k([B]0-[A]0) where k is the rate constant and [A]0 and [B]0 are the initial concentrations of reactant A and reactant B respectively