Acta Phys. -Chim. Sin. ›› 1992, Vol. 8 ›› Issue (01): 52-58.doi: 10.3866/PKU.WHXB19920111

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Studies on Kinetics of the Electron Transfer Reaction Between Eu(II) and Xylenol Orange by Stop-Flow Method

Li Da-Zhen; Liu Cheng-Min; Xiao Yang-Tian; Yang Hui-Xing; Han De-Gang   

  1. Chemistry Department, Beijing Normal University Beijing 100875; Chemistry Department, Beijing University 100871
  • Received:1990-09-04 Revised:1991-03-02 Published:1992-02-15
  • Contact: Li Da-Zhen

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Abstract: The kinetics and mechanism of the reaction between Eu~(2+) and Xylenol orange (XO) in aqueous solution has been studied by means of stop-flow spectrophotometric method. The kinetic parameters of the rate-controlling step, i,e, reaction order (n=2), rate constant at various temperatures (k_(278 K)=5.7×10~8 L·mol~(-1)·s~(-1), k_(338 K)=1.01×10~9 L·mol~(-1)·s~(-1)…), activation energy (E=7.6×10~3 J·mol~(-1)) and preexponential factor (A=1.5×10~(10) L·mol~(-1)·s~(-1)) have been determined. It has been established that the electron transfer reaction between Eu~(2+) and XO is a diffusion controlled reaction.
The possible mechanisms of the reaction between Eu~(2+) and XO both in the presence of excess XO and Eu~(2+) also have been suggested. The relation between the rate constants of each step were estimated.

Key words: Eu2+, Xylenol Orange, Reaction, Stop-Flow Method