Lab Chem 3 :Kinetics-factor affecting rate of reaction

Discussion I) Determination of rate law and rate constant The experiments are conducted based on the rate law, Rate = k  [I-]  [I-]n [S2O82-]m where k is the rate constant while n  and  and m are the reaction orders of I - and S2O82- respectively. As reaction orders, n  and  and m  are   are defined as the power to which the concentration of that reactants is raised to and must be determine experimentally. n and m  are   are experimentally determined to be 1. This means that the reaction is first order with respect to [I -] and first order with respect to [S 2O82-]. The overall order of reaction is 2. In the study of the effect of concentration on the rate of a reaction, it was found that when increasing the concentration of a reactant, the reaction time getting slower thus increasing the rate. The collision theory explains the phenomenon by stating that molecules must collide in the right orientation and possess a certain minimum kinetic energy, called the activation energy to initiate the chemical reaction. An increase in the concentration of reactants leads to an increase in the number of reactant molecules having energy equal to or greater than the activation energy. Hence, increase the collision frequency. The increase in the effective collision leads to an increase in the reaction rate. II) Effect of temperature on reaction rate Based on the results of this experiment, it shows that the rate of reaction increases as temperature increases. Using the Arrhenius equation, k=A -Ea/RT 

the activation energy, E A   can be determined by keeping the concentration of all the reactants constant while varying the temperature for each experiment. According Accord ing to the Arrhenius equation, a slight deviation in temperature will change the reaction rate significantly. A slight increase in temperature increases the number of colliding particles with activation energy and consequently, reaction rates significantly. So, since slight deviations in temperature may affect reaction rates significantly, the temperature at which the experiment was carried out must be kept constant. The conical flasks were placed in an ice bath to maintain the reaction temperature. There were several changeability above and below the desired temperatures. Moreover, the time taken for the blue solution to turn colourless is relatively longer for the lower temperatures which creates

a greater possibility for error. Keeping the temperatures constant can be done by conducting the experiments in hot plate. During the experiment, there were have factors that may affects the results. Reactants were poured imprecisely into the conical flask. There may be leftover reactants in the measuring cylinder and some reactants may stain the sides of the conical flask during the addition. This reduces the concentration of the reactants in the conical flask. Pipetting the reactants into the conical flask would ensure that the reactants are added in the required quantities and the ultimate results are accurate. There is inaccuracy as the stopwatch was stopped only when a random colour intensity was observed. There should be a harmony between lab partners as to when the stopwatch should be stopped. All glassware used in this experiment must be kept clean and dry to prevent contamination. The solutions should be poured into small beaker before we measured the volume. The overall volume of the solution was also kept constant at 50mL by adding distilled water to standardize the conditions of the reaction environment, thus increasing the accuracy.

Reference Lab Report on Chemical Kinetics, 2011. Retrieved from http://www.art-xy.com/2011/10/lab-

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