Kinetics of the reversible reaction between arsenious acid and aqueous iodine

✍ Scribed by J. N. Pendlebury; R. H. Smith

• Publisher: John Wiley and Sons
• Year: 1974
• Tongue: English
• Weight: 967 KB
• Volume: 6
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550060505

✦ Synopsis

Ihe kinetics of the reversible reaction H s A s O ~ + 13-+ HzO Z? H ~A s O ~ + 2H' + 31have k e n studied spectrophotometrically in acid solution under conditions in which both the forward and reverse reactions go to virtual completion and in which the reaction comes 10 a practical equlibrium. The rates of rhe forward (I?,) and reverse ( R r ) reacrions are givm b y

u. and u have the values (4 =t 1) X 10-j mole/'l. . S , (4.2 =k 0.2) X 10-j mole2 I.*.s. (5.0 =t 0.3) X lo-' m ~l e ~/ I . ~. s . ( 1 . 1 f 0.1) X I.zjmole2.s, and (3.7 + 0.2) X 10-3 1.3/mole3.s at 298.2"K and at an ionic strength of 2.00M maintained by adding sodium chloride. The stoichiometric equilibrium constant under similar conditions is 0.022 + 0.003. Different values of these parameters were obtained when sodium perchlorate and sodium nitrate were used to control ionic strength. The results are compared with those from previous reports and a mechanism is proposed hased upon an initial rapid equilibrium H ~A s O ~ + I ? S H J A s O ~I + + 1lollowed by a rate-determining attack of water upon HaAsOd+. HyAsO3I. and HAsOaI-.