By comparing the results from Tables 2, 4 and 6 with equation (6), the rate
coefficient values can easily be obtained from each set of experiments (described in
detail in student handout): k = 16.6 L2
mol−2
s−1
; 15.3 L2
mol−2
s−1
(16.6 L2
mol−2
s−1
);
29.5 L2
mol−2
s−1
(28.5 L2
mol−2
s−1
), respectively. (The values given in parentheses
are obtained by the linear regression analysis of the data measured in the last two sets
of experiments).
The oxidation of thiosulfate to tetrathionate by ferric ions (8) is another redox
reaction taking place in the system investigated (7,8):
3+ 2- 2+ 2-
2 3 4 6 2Fe + 2S O 2Fe + S O → (8)
This reaction however has no significant influence on the experiments conducted. The
reaction followed is zeroth order with respect to thiosulfate and second order with
respect to iodide, clearly indicating that reaction (8) does not interfere significantly
with the kinetics of the reaction studied.