首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Exact Concentration Dependence of the Landolt Time in the Thiourea Dioxide-Bromate Substrate-Depletive Clock Reaction
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Exact Concentration Dependence of the Landolt Time in the Thiourea Dioxide-Bromate Substrate-Depletive Clock Reaction

机译:抗锚硫酸盐 - 溴酸盐基质耗尽钟反应中的抵抗时间的精确浓度依赖性

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The thiourea dioxide (TDO) bromate reaction has been reinvestigated spectrophotometrically under acidic conditions using phosphoric acid-dihydrogen-phosphate buffer within the pH range of 1.1-1.8 at 1.0 M ionic strength adjusted by sodium perchlorate and at 25 degrees C. The title system shows a remarkable resemblance to the classical Landolt reaction, namely, the clock species (bromine) may only appear after the substrate TDO is completely consumed. Thus, the title system can be classified as substrate-depletive clock reaction. Despite the well-known slow rearrangement characteristic of TDO in acidic solution, it is surprisingly found that the Landolt time of the title reaction does not depend at all on the age of TDO solution applied. It is, however, shown experimentally that the inverse of Landolt time linearly depends on the initial bromate concentration as well as on the square of the hydrogen ion concentration. In addition to this, it is also noticed that dihydrogen phosphate markedly affects the Landolt time as well, and this feature may easily be taken into consideration by the H2PO4- dependence of the rate of bromate-bromide reaction quantitatively. Based on the experiments, a simple three-step kinetic model is proposed from which a complex formula is derived to indicate the exact concentration dependence of the Landolt time.
机译:在酸性条件下使用磷酸 - 二氢 - 磷酸盐缓冲液在1.1-1.8的基质强度下通过高氯酸钠和25℃调节的离子强度,在酸性条件下,在酸性条件下,在酸性条件下,在酸性条件下已经在酸性条件下重新激活了分光光度法的反应。标题系统显示与古典抵抗反应显着的相似性,即时钟物种(溴)只能出现在衬底TDO完全消耗之后。因此,标题系统可以被归类为基板耗尽时钟反应。尽管酸性溶液中TDO的众所周知的缓慢重新排列特性,但令人惊讶地发现标题反应的抵抗时间根本不依赖于所施加的TDO溶液的时代。然而,实验示出了抵抗时间线性的逆相反地取决于初始溴酸盐浓度以及氢离子浓度的平方。除此之外,还注意到磷酸二氢化合物也显着影响抵抗时间,并且可以通过定量溴酸盐 - 溴化物反应的速率容易地考虑该特征。基于实验,提出了一种简单的三步动力学模型,从中得出复合公式,以指示抵抗时间的精确浓度依赖性。

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