Atkins & de Paula:
Physical Chemistry for the Life Sciences
In the method of initial rates the rate is measured at the beginning of the reaction for several different initial concentrations of reactants. The rate law is given by
Where v0 is the initial rate (mol L-1 s-1), [A]0 is the initial concentration of reactant A (mol L-1), a is the reaction order, and k is the rate constant. The units of k depend on a and are given by mol(1-a) L(a-1)s-1.
For a series of initial concentrations, a plot of the logarithms of the initial rates against the logarithms of the initial concentrations should be a straight line with slope a.
To determine the orders of reaction with respect to reactants A and B enter the initial
concentration of [A] in row 1 (red items), the initial concentration of [B] in column 1 (blue items), and the
corresponding rates for these initial concentrations. Click Plot - log[A] to see the logarithms
of initial rates plotted against the logarithms of initial concentrations of reactant [A].
Click Plot - log[B] to see the analogous plot of reactant B. The Least-Squares Analysis
tab shows the average slope of each reactant (i.e., order of reaction with respect to that reactant).