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UIUC CHEM 203 - Kinetic Studies of the Ferroin Complex (Recovered)

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Kinetic Studies of the Ferroin ComplexAbstractIn this lab, the ferroin complex was studied and different aspects having to do with rates were determined by performing four different types of reactions with three different solutions. Only one of these solutions (HNO3) was analyzed in this procedure. The four different reactions were performed at different temperatures and the absorbance was measured by a spectrophotometer 20 as the reactions proceeded. A control was also run as the fourth reaction which was a hydrolysis reaction. IntroductionThe process of using Kinetic studies to determine rate laws and mechanisms for reactions is highly used in science in the real world. In medicine a group in Yemen used spectrophotometric process to determine anti-Parkinsonian and antiviral drugs to use. They used two cost effective methods to develop different kinds of drugs1. Also this type of spectrophotometric methods were used in the determination of iron and boron in soil2. Finally it is also seen in pharmaceuticals with tofisopam and the use of spectrophotometyric principles to determine mechanisms that work best for the enhancing of drugs used in the world3. There are four main goals of this lab. These goals include: the determination of a rate of a chemical reaction, the determination of the rate law for the reaction, the proposition of a mechanism for the reaction and the determination of the activation energy. Many of these ideas will be seen after the completion of the lab because they have to be calculated. Ferroin will be studied heavily in this reaction. Ferroin is a deep red colored coordination complex that absorbance vs. time graphs can be obtained and rate laws can be calculated and constants can be found just by studying this complex spectrophotometrically. If [ferroin] vs. time is a straight graph is straight, the reaction order is zero, if the ln[ferroin] vs time is straight, the reaction is first order, if 1/[ferroin] vs. timeis straight, the reaction is second order. Also after the reactions take place and data has been gathered, a pseudo-order process will be used to determine the order of the reaction for the non-ferroin complex by comparing concentrations of the ferroin complex and the non-ferroin complex. For any confusion, look to the lab manual4. Chemical kinetics is defined as the study of the rates of chemical reactions and mechanisms by which they occur4. This process will be used to determine the rate laws and mechanisms of the reactions with ferroin in this lab. Also the rate of a chemical 2reaction is defined as the change in concentration of a reaction with respect to time. The rate law of a reaction is determined experimentally. The rate law shows how the mechanism works and the general formula looks as followsRate = k[A]x[B]yK is the rate constant which depends on temperature but is independent of the concentrations. K is determined by following a concentration through a species in a reaction with time, and X and y are the order of the concentrations and the sum of these two is the overall order for the reaction. A and B are the different solutions that are present together. The rate determining step of a reaction is the slowest step of a reaction because the overall reaction cannot be faster than this step. One of the main equations used in this lab is Beer’s law. Beer’s law is as follows:Abs = εl[F]Beer’s law describes absorbance by path length “l” absorptivity constants “ε” and the concentration “[F]”. When a=0 the order of reaction is zero, when a=1 the order is one, when a=2 the order of reaction is 2. Finally microscopic information about the reaction can be shown by the Arrhenius equation. This equation is as follows:k = Ae-Ea/RTA is the pre-exponential factor, Ea is the activation energy, T is temperature in Kelvin and R is the gas constant. The pre-exponential factor relates collisions or dissociation behavior to the rate4. The activation energy is the minimum energy required in the rate determining step. -Ea/R equals the slope of the line of the reaction and ln(A) is the y intercept. Finally in this lab there will be new equipment. This includes a Dri-bath and a spectronic 20. Both of these are very sensitive and care should be taken when being used. Also a catalysis is an accelerant of a chemical reaction. Materials and MethodsFor this lab, the full procedure can be found in the lab manual. System C, the effects with ferroin in HNO3 was observed in this lab report. For most aspects of the lab, the procedure was followed very closely and very few deviations were made. The temperatures in the Dri-baths were exactly right, and the amount of solutions used were the exact values that they needed to be. One of the things that was changed, the 3hydrolysis reaction was not run for 15 minutes, it was run for 7.5. Also the point at whichthe experiments was stopped was not always exactly 10% of the original absorbance. For experiment I, the initial absorbance was .288 and the final was .026. For experiment II, the initial was .288 and the final was .020. For experiment III, initial was .288, and final was .020. The following experiments were runI Experiment 1 at 40ºCII Experiment 2 at 40ºCIII Experiment 1 at 55ºCIV Hydrolysis at 55ºCExperiment 1 was run for 19.5 min, experiment II was run for 18.5 min, experiment III was run for 5.5 min, and the hydrolysis as stated before was run for 7.5. The materials used that were new techniques. Also the sample data that was provided was used for the remainder of the lab.ResultsThe reactions for the experiment were as follows and will be used for the majorityof the results and discussion. This also can be seen from the lab manual4.Table 1, Makeup of the reactionSystem Expirament Makeup of the reaction before FerroinC 1 0.6 mL 1.0 M HNO3 + 2.1 mL H2OC 2 1.2 mL 1.0 M HNO3 + 1.5 mL H2OIn the first table, the results show the initial molarity and temperature of the HNO3solution created. Each of these components have a different effect on the absorbance and rate of reaction. The temperature was carefully measured and the amount of DI H2O and HNO3 were measured with a volumetric pipet to ensure the accuracy of the amount of solution used. The temperature was carefully maintained through a dri-bath. The sample calculations can be seen below the table Table 2 Original Solution of HNO3 and H2OSystem Experiment Temperature Amount 1 Amount Amount Molarity4C (ºC) M HNO3 (mL)HNO3 (mol)H2O (mL)


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UIUC CHEM 203 - Kinetic Studies of the Ferroin Complex (Recovered)

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