Question

Describe one method to determine rate law and order of a reaction.

Answer 1

Integrated rate law method is the method to determine rate law and order of a reaction. In this method, the concentration of reactant undergoing a reaction is measured at different time intervals. This time-concentration data is substituted in the integrated rate laws of reactions of different orders. The constancy of the values of rate constants determines the correct order of the reaction. It can also be tested graphically.

The rate constant and order can be determined from the resultant straight-line plot between concentration of the reactant (a − x) and time (t).

a) If the plot of (a − x) versus t is a straight line with a negative slope, the reaction follows the zero-order kinetics.

b) If the plot of log (a − x) versus t is a straight line with a negative slope, the reaction follows the first-order kinetics.
c) If the plot of $\frac{1}{\left(a-x\right)}$ versus t is a straight line with a positive slope, the reaction follows the second-order kinetics.