Chemical Kinetics - Lab Report Example

Lab Partner’s Group Number Section Number DD Month YYYY of the Experiment: CHEMICAL KINETICS Tableof Contents Introduction 1 Experimental Procedure 3 Results 4 Discussion 5 References 7 Introduction The main objective of the experiment was to find out the rate constant and the rate law when oxalic acid reacts with permanganate. Chemical kinetic is a term that is normally used in describing studies associated with the rates of chemical reactions. Chemical reactions is a process, therefore, it takes some time to react. The reaction time can even take more than hours or even microseconds (Sen, 176). The chemical reaction rates was found through the assessment of the product or the reactant over a certain period of time. Irrespective of the reactant chosen in determining the rate, the outcome will always be similar. However, it is quite imperative to note stoichiometric ratio for the components. For instance, assuming product A and Product B reacts as shown in the following formula . The reaction rate can be represented as a variable and function of each product and reactant as shown below For every reactant, it was normally assumed that the concentration was decreasing, the moment the reaction occurred. For this reason, to prove the positivity in the rate, a negative value is used. On the other hand, the product’s concentration was on a rising trend when the reaction proceeded. The measurement of the reaction rate was done in various ways. This involved accurately measuring changes in the concentration as one reaction occurred simulteneously. The experiment utilized a visual change of the reactant’s color used. Therefore, since the visual indications are always in a subjective manner, we performed the experiment severally. Additionally, the change in color indicated that the reactant’s concentration reached zero, therefore, the experiment measured the mean reaction rate for the whole process. The rate law of the reaction described the relationship of the reaction rates to the reactants reaction. Using a similar generic reaction, the rate law used the following formula From the model, k represented the rate constant for the experiment, while y and x represented the reaction order for B and A respectively. The experiment did not acknowledge x and y are stoichiometric coefficients from a and b (Mathews, Van Holde and Ahern, 765). The reaction order value was determined with the help of the experiment. The group did not use the balance chemical equation to find one. The reaction orders were determined with the help of the initial rates method, where the experiment was conducted varying the reactant’s concentration while maintaining others. In the reaction time, the resultant change was used to find out the rate order for the reactant. Experimental Procedure In the experiment, the various concentrations of the potassium permanganate and the oxalic acid were mixed together. The experiment also recorded the time needed for the mixture to change color from dark purple to brownish yellow. The sample run was performed before any data was recorded. This was important because it made it possible to understand what the experiment is all about and the expected outcome. Three trials were carried out because the end points are not always easy to see. In situations where the time differed for more seconds, trials were repeated. The solutions were clearly labelled to make sure that there are no cases of solution contamination. To start off the experiment, 10ml graduated cylinders and the disposable droppers were obtained. Additionally, 2 150ml beakers were also obtained. The droppers, beaker, and cylinder were labelled with the solution necessary for this experiment. This was important because it ensured that there is no cross-contamination that is likely to occur in the entire experiment. The Pottasium Per Manganate remained in the hood this was important because it made it easy to be obtained any time. The molarity of the solution was written down in Data Table 1. 70 mL of the Oxalic acid was obtained that was in the hood (Laberge, 75). The other beaker was filled with the water that was deionized and the thermometer was placed in the water. The temperature was given time to equilibrate and was later recorded in the Data Table 1. The Pyrex tube was obtained from the hood and then small stir bar was placed in it. Tube was then clamped above the stir plate and then tested out a good speed of the stir for the stir bar. The still bar was stirred in a controlled manner so that the test tube cannot be damaged. Water and Oxalic acid was then added in the first experiment. Potassium permanganate was added carefully to the solution last, timer was then started immediately after the whole solution. The timer was stopped after the solution turned golden yellow. The second and the third experiment was performed in the same way. Results Data Table 1 Experiment Temperature Reaction Time (Sec) Average Reaction Time (Sec)     Trial 1 Trial 2 Trial 3   1 20 331.2 328.8 325.2 328.4 2 20 193.8 190.2 185.4 189.8 3 20 254.4 262.2 268.4 261.6666667 The concentration of reactant for the Oxalic Acid was 0.7550 M, while that of permanganate was 0.13004. These concentrations were obtained from the bottlers that were positioned at the hood. When determining the concentration for the reactance, the compound with a limiting reactant was determined. Additionally, the compound that was in excess was also determined. This is shown in the data table 2. The Data table 2 also recorded the change on the concentration for the reactants. Data Table 2 Determination of the Rate Order for Oxalic Acid Experiment Oxalic Acid (initial) Oxalic Acid (initial) Change in Oxalic Acid Reaction Time (Sec) Rate (M/s) 1 0.3146 0.2989 0.0162 328.4 1.684*10^-5 2 0.6292 0.6127 0.0162 189.8 1.684*10^-5 Determination of the Rate Order for Permanganate Experiment Manganate (Initial) Manganate (Final) Change in Manganate Reaction (Sec) Rate (M/S) 1 0.0108 0 0.0108 328.4 1.644*10^-5 2 0.0217 0 0.0219 261.64 0.004*10^-5 Discussion In the experiment, the reaction was timed essentially till the end. The average reaction rate was measured against the instantaneous reaction rate (Charters, 10). It was important to make the distinction so that to prevent any possible contamination that might arise. Additionally, the rate of chemical reaction was hypothesized from the concentration of the reactant at the end of the experiment. From the experiment, it was found out that permanganate was a limiting reaction. This is because the final concentration was zero as shown in the data table 2. On the other hand, Oxalic acid was the compound that was in excess. This was obtained from the stoichiometric ratio that was calculated between Oxalic acid and the permanganate (Akiyama and Otto, 1781). Other ways that scientists can measure the reaction rates is dependent on the outcome. Assuming the pH changes, then one needs to watch the reaction with the help of a meter. Scientists could also take samples from the chambers of reaction and run the sample in a chromatography system which separates then into different parts. In the beginning there will be only reactant. After sometimes a new signal will be observed. This is normally relevant to slow reactions. It was important for the experiment to have the same volume to create uniformity in the outcome. This was helpful to come up with a uniform concentration and thus correct results. The difference between the rate constant and the reaction rate is that the rate constant is proportionality constant in the rate of equation law and is equated to the reaction rat when the concentration of the reaction is uniform. On the other hand, the reaction rate is the concentration change of a reactant of the product per unit second. Three trials were carried out because the end points are not always easy to see. In situations where the time differed for more seconds, trials were repeated. The solutions were clearly labelled to make sure that there are no cases of solution contamination. Additionally, the catalyst was used just to speed up the reaction. It did not affect the result (Akiyama and Otto, 1779). During the experiment, human error and statistical error was experienced during miscalculation. This can be avoided by being keen. In addition, there was system error especially on thermometers when measuring the temperature, this was as a result of inconsistent. This will be avoided by not using worn out thermometers in future. References Akiyama, T., and F.D. Otto. Mass Transfer With Chemical Reaction For Arbitrary Bodies—Infinitely Fast Homogeneous Reaction. Chemical Engineering Science 26.10 (1971): 1779-1781. Web. Charters, Maria. Florida International University. ACM SIGCSE Bulletin 47.1 (2015): 3-3. Web. Laberge, Monique. Biochemistry. New York: Chelsea House, 2008. Print. Mathews, Christopher K, K. E Van Holde, and Kevin G Ahern. Biochemistry. San Francisco, Calif.: Benjamin Cummings, 2000. Print. Sen, Asok K. Mass Transfer With Chemical Reaction—I. A Second-Order Irreversible Reaction.Chemical Engineering Science 42.9 (1987): 2075-2083. Web. Read More