The purpose of the Kinetics experiment is to determine the rate expression of a mixture. Through the process of the experiment, students will also study rates of reactions and be able to determine reaction orders.

The experiment compares three mixtures, composed of three separate solutions in varying concentrations, with equal volumes. By doubling the concentration of one solution in the second mixture, the experimenter can calculate the change in rate and compare the result to the initial result. The affected change of rate for the second solution can be determined by doubling it's concentration while reducing the first solution back to the initial concentration. I theorize that the rate of reaction will be first order in concentration for each solutions and second order overall.


OXIDATION, REDUCTION, AND BALANCED EQUATIONS

-1 -2 -2 -1
IO3 + SO3 -----> SO4 + I

I = +5 -> I = -1
S = +4 -> S = +6


-2 -2 -
Ox: SO3 -> SO4 + 2e

-2 -2 -
SO3 + H20 -> S04 + 2e

-2 -2 -
3SO3 + 3H20 -> 3S04 + 6e


-1 - -1
Red: IO3 + 6e -> I

-1 - -1
IO3 + 6e -> I + 3H20


Balanced Equation

-2 -1 - -2 - -1
3SO3 + 3H20 + IO3 + 6e -> 3S04 + 6e + I + 3H20

-2 -1 - -1
3SO3 + IO3 -> 3S04 + I



PROPOSED MECHANISM #1

-2 -1
SO3 + IO3 <----> IO3-SO3'

-2 Slow!
SO3 + IO3-sO3' ----> IO3-SO3-SO3'

-2 -2 -2 -2 -1
SO3 + IO3-SO3-SO3' ----> SO4 + SO4 + SO4 + I

-2 -1 - -1
3SO3 + IO3 ----> 3S04 + I



-2 1 1
R = k[SO3 ] [IO3-SO3'], where IO3-SO3' is an intermediate step.

-2 -1
[IO3-SO3'] = [SO3 ][IO3 ]


-2 1 -2 1 -1 1
R = k[SO3 ] [SO3 ] [IO3 ]

-2 2 -1 1
R = k[SO3 ] [IO3 ]


The experimental rates of the mixtures prove to be first order in Iodate, second order in Sulfite, and third order overall. The theoretical rate had stated that both solutions of Iodate and Sulfite would be first order, and that the mixture would be second order overall. Therefore, the experimental and theoretical rates do not match. In both cases, it is interesting to note that the concentration of the third solution, water, has no effect in either case. From this we can conclude that the concentration of the water is zero order.

The experimental rate could have been incorrectly calculated if the concentration of the solutions were inconsistent in the mixtures. These values would have changed the Molarities in the mixtures, and affect the rate at which the product forms. While the data recorded would still indicate that the mixture is third order overall, the actual rate may have been closer to the theoretical. Alternatively, the rate may have been fourth order overall or greater. The experimental rate could have also been incorrectly recorded through discrepancies in the calculations, where the rate could be determined as being an overall order greater, or less than, that of third order. In this case, the issue that arises would be the inverse that of the previous conflict.

Also, college sucks.