Lab 91-syikin - Experiment 91 Kinetics of Reduction of...

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Experiment 91 Kinetics of Reduction of Toluidine Blue by Sulfite Abstract The purpose of this experiment is to investigate the effect of the ionic strength on the rate of reaction of toluidine blue and sulfite. It is observed that as concentration of sulfite increases, k 1 increases. Furthermore, it is observed that as concentration of NaCl increases, k 1 decreases. In this experiment, Debye Huckle model was employed to get A’ value. For low concentrations (low ionic strength), Debye Huckle limiting law was used to get A’ value of 0.47 ± 0.17 1 2 liter mol . Debye Huckle limiting law was also used to fit the entire range of ionic strength and the value of A’ was found out to be 0.27 ± 0.05 1 2 liter mol . Lastly, the extended Debye-Huckle model for higher ionic strength was used to fit the data and the value of A’ was found out to be 0.58 ± 0.06 1 2 liter mol . 1
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Introduction This experiment investigates the ionic strength dependence on the reaction rate. The reaction of interest is as follows : TB + + SO 3 2- + H 2 O TBH + SO 4 2- + H + Various combination of concentration of reactants was experimented. The reaction was run in a vial at room temperature for 30 minutes and the reduction of toluidine blue by sulfite was observed by using Ocean Optics Spectrometer. The absorbance as a function of time is proportional to the TB + concentration. The integration of rate law (with assumption that [sulfite] >> [TB + ] ) leads to the following equation : t k sulfite TB 1 ] [ ] [ ln - = + Therefore, the slope of a graph of ln (absorbance) vs. time is needed to determine the value of k 1 for every reaction. To employ Debye-Huckle model and to determine the values of A’, a plot of log k 2 vs. √I was graphed and the slope of that graph was used to get A’ value. 2
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Run 1 2 3 4 5 6 7 [Na 2 SO 3 ] (M) 0.040 0.040 0.040 0.040 0.020 0.010 0.005 Time (s) Absorbance 0 0.4066 0.6007 0.6445 0.5468 0.6430 0.7291 0.7571 30 0.3847 0.5664 0.6019 0.5135 0.6135 0.7069 0.7372 60 0.3631 0.5339 0.5715 0.4824 0.5868 0.6887 0.7219 90 0.3422 0.5022 0.5382 0.4539 0.5629 0.6656 0.7089 120 0.3231 0.4737 0.5092 0.4282 0.5430 0.6512 0.7034 150 0.3040 0.4488 0.4716 0.4000 0.5162 0.6369 0.6896 180 0.2885 0.4154 0.4449 0.3736 0.4951 0.6158 0.6717 210 0.2722 0.3913 0.4153 0.3502 0.4736 0.5968 0.6657 241 0.2576 0.3686 0.3949 0.3268 0.4550 0.5807 0.6567 271 0.2416 0.3450 0.3693 0.3053 0.4384 0.5678 0.6452 301 0.2301 0.3261 0.3447 0.2885 0.4170 0.5524 0.6352 331 0.2162 0.3036 0.3263 0.2697 0.4019 0.5410 0.6280 361 0.2045 0.2884 0.3047 0.2533 0.3849 0.5266 0.6202 391 0.1949 0.2700 0.2874 0.2374 0.3693 0.5143 0.6119 421 0.1816 0.2544 0.2690 0.2260 0.3538 0.5028 0.6020 452 0.1717 0.2394 0.2548 0.2115 0.3381 0.4881 0.5914 482 0.1639 0.2239 0.2407 0.2001 0.3240 0.4804 0.5884 512 0.1557 0.2108 0.2251 0.1874 0.3141 0.4659 0.5799 542 0.1477 0.2001 0.2125 0.1776 0.3016 0.4571 0.5739 572 0.1396 0.1887 0.2007 0.1674 0.2901 0.4459 0.5671 Table 1. Absorbance data for reactions of 5.0 x 10
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Lab 91-syikin - Experiment 91 Kinetics of Reduction of...

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