Calculation of the Rate Constant

                This is the equation for the rate constant for a second order equation (The Acetone Iodine reaction is second order):

[Acetone]0 is the initial concentration of acetone,  [H+]0 is the concentration of protons from the acid and X is the concentration of acetone enolized or the amount reacted up to time t. It can be rearranged to obtain:

This equation clearly shows that a graph of α as a function of time should produce a graph of a straight line with a slope equal to the rate constant k. The only unknown term in the equation is X. It can be calculated from the initial absorbance and the absorbance at time t using the following equation:

 A0 is the initial absorbance, At is the absorbance at time t, Є is the molar absorption coefficient at 470nm for iodine (225 M-1cm-1), and l is the path (1cm).