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IntroductionChemical kinetics is the study of the rates at which reactions occur Since it is related to chemical reactions it is a major component of general chemistry and is integral to all chemical processes The importance of studying chemical kinetics is that by studying chemical kinetics chemists are able to predict the duration of a reaction and manipulate the speed at which it occurs Four major variables affect the rate of reaction temperature surface area catalysts and concentration of reactants In this lab we kept the temperature constant and tried as best as we could to avoid contamination of the reactants This is to ensure that the only variable changing was the concentration of reactant It is important to note that the surface area contact of the two reactants can be overlooked as long as the solution is well mixedThe order of reactions is an important part of understanding the rates of reaction The total order of the reactants is found by summating the exponents n and m in the following equation nmRatekABfor the reaction ABC This general rate equation represents a relationship between the rate of the reaction to the concentration of the exponents raised to the exponents n and m which are each partial orders of the reaction with respect to their reactant The constant k is the rate of constant for that specific reaction at that temperature and its units vary depending on the order of the reactionThe order of a reaction can be calculated by using one of two methods though neither use the stoichiometric equation of the reaction to determine the order The first method is an examination of the experimental data and determining the effect of an increase or decrease of the concentration of a reactant on the overall rate of the reaction The other method is by plotting a graph of the concentration of a reactant or a value that can represent the concentration in our case we used the absorbance of light by one of the reactants as a function of time Using the graph method we simply take the slope of a line tangent to the graph which is the instantaneous rate of the reaction The net reaction that occurs in this experiment can be expressed in the following equationCrIIIEDTACrIIIEDTAComplexaqaqaqTherefore the rate of reaction equation is the followingHaRatekCrIIIaqThe objective of the lab was to determine the partial order of the reaction with respect to the chromium III ion The concentration of Hydrogen ions from the EDTA solution used was kept constant fairly high in order to maintain that the change of concentration of EDTA could be overlooked and we could attribute the changes in rate of reaction to the chromium III ion only Using three trials with three different pH values 40 45 and 50 for the EDTA solution would allow us to confirm the results from one trial with the results of the othersIn this experiment we used the absorbance of light by the solution as the reaction takes place as the value for the concentration of Cr III ion It was given that absorbance and concentration are directly proportional through the BeerLambert LawAbc
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