Reactions with other oxidation levels of halogens

2 Reactions with other oxidation levels of halogens 

At 25 °C, the equilibrium constant for (1) is 4.7x10 so that the forward reaction can be studied only in fairly acidic solution. At high chloride concentration, the stoichiometry departs from that of equation (1), more chlorine being formed, via reaction (2). The reaction is retarded by chlorine but not by CIO2 , and is of overall eight order , viz. 

Recent work on these reactions by Rapson et al. has been summarized . They have measured (spectrophotometrically) initial rates of formation of chlorine dioxide in moderately strong sulphuric acid solutions (to 6 M). The order in total sulphuric acid concentration is found to be 12-13 when the molal activity of sulphuric acid is calculated, the order is 4.4-4.5. The order in chlorate is close 

Salt effects will undoubtedly be responsible for some variations of the apparent orders, but until full publication is available it seems that the high-order rate expressions should be accepted provisionally , and not written off . 

When iodide ion is also present, the reaction is fourth order , with the rate expression 

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