Using the data in the table, find the value and units of the rate constant, k, and then write the complete rate law equation for this reaction.

Question

Using the data in the table, find the value and units of the rate constant, k, and then write the complete rate law equation for this reaction.

Answer 1

Shelly,

From your previous problem, I should you how to find the order with respect to each reactant. We found it to be 1st order in H₂O₂, 1st order in I^- and zero order in H⁺. Thus we can write the rate law as ...

Rate = k[H₂O₂][I^-]

To find k, we simply choose ANY trial and use the rate and the concentrations from that trial, and calculate k.

I will use trial 1 as an example, where the rate is given as 1.15x10^-6 mol/Ls ...

1.15x10^-6 mol/Ls = k[0.01 mol/Ls][0.01 mol/Ls)

1.15x10^-6 mol/Ls = 1x10^-4 mol²/L²s² k

k = 1.15x10^-2 M^-1s^-1 (note that mol/L = M so we can write the units as M/s or M^-1s^-1)