calculated from a least-squares fit to the Eyring plot. The ionisation constant pK1, was inferred from the kinetic data at 303 K to be 7.22. Beyond pH 9, the reaction is markedly retarded and ceases completely at pH ⩾ 11. This inhibition was attributed in part to the continuous loss of the catalyst as a result of the simultaneous oxidation of Cr(III) to Cr(VI).
在各种温度下,在
硝酸盐水溶液[μ= 0.10 M(KNO 3)]中研究了[Cr(III)Y]
水溶液(Y为
EDTA阴离子)与
过氧化氢的反应速率。一般的速率方程式,Rate = [Cr(III)Y] aq [H 2 O 2 ]在pH范围5–9内成立。据信,H 2 O 2的分解反应通过两个途径进行,其中
水合和羟基-五齿的
EDTA络合物均充当催化剂中心。提出了取代控制机制,并给出了二阶速率常数k 1和k 2的值。在303 K时,分别为1.75×10 -2 M -1 s -1和0.174 M -1 s -1,其中k 2是
水生物种的速率常数,k 2是羟基络合物的速率常数。各自的活化焓(ΔH * 1 = 58.9和ΔH * 2 = 66.5 KJ mol -1)和活化熵(ΔS * 1 = -85和ΔS * 2 = -40 J mol -1 deg -1)是根据与Eyring图拟合的最小二乘法计算得出的。从303