Explore BrainMass

Reaction Kinetics

In aqueous solution, the reaction of A to form B has the following rate expression:

-d[A]/dt = k[A]{1 + k'[H+]}

From the pH dependence of the reaction, k' was found to be 1.0 x 10e5 M-1. In a pH 4.0 buffer, it took 5 min for a 0.30 M solution of A to react to give 0.15 M solution B. Calculate the value of k and give its units.

I am aware that the pH 4.0 buffer solution reflects the H+ ion. Using the antilog (10^-4.0) of the 4.0 buffer will give you the concentration of H+ present in the solution. The value calculated is 0.0001 M.

-d[A]/dt = k[A]{1+ (1.0*10e5 M-1)*(0.0001M)}
= k[A]{1.00}

Since this is a first order rate law, is it possible to use the integrate form ln[A]t/[A]o = -kt, rearranging the equation and solving for k.
Since A reacts to form B the rate of appearance of B expression would be d[B]/dt =k[A], you know what the concentration of A (0.30M), and you know what the concentration of B (0.15) is. The time(s) is know so can it just be substituted into the equation? I'm not sure where to start.

Solution Summary

The expert examines reaction kinetic equations. The solution is a step-by-step equation.