Chapter 13, Problem 13.73QP

Chlorine dioxide oxidizes iodide ion in aqueous solution to iodine; chlorine dioxide is reduced to chlorite ion.

$2{\text{ClO}}_2(aq)+2{\text{I}}^{-}(aq)\stackrel{}{\to }2{\text{ClO}}_2{}^{-}(aq)+{\text{I}}_2(aq)$

The order of the reaction with respect to ClO₂ was determined by starting with a large excess of I⁻, so that its concentration was essentially constant. Then

$\text{Rate}=k{[\text{ClO}2]}^m{[{\text{I}}^{-}]}^n=k^{\prime }{[{\text{ClO}}_2]}^m$

where k′= k[I⁻]ⁿ. Determine the order with respect to ClO₂ and the rate constant k′ by plotting the following data assuming first- and then second-order kinetics. [Data from H. Fukutomi and G. Gordon, J. Am. Chem. Soc., 89, 1362 (1967).]

Time (s)	[ClO2] (mol/L)
0.00	4.77 × 10−4
1.00	4.31 × 10−4
2.00	3.91 × 10−4
3.00	3.53 × 10−4
5.00	2.89 × 10−4
10.00	1.76 × 10−4
30.00	2.4 × 10−5
50.00	3.2 × 10−6