The rate order, which depicts the effect of the reactant incinerations on the overall rate of the reaction, can only be experimentally determined. One of the methods that can be used in the determination of the rate order is the integrated rate law model, which tries to linear the concentration and time by fitting it into particular graphical format. Zero order reaction is modeled through concentration v time, 1st order model through Len[A] v time , while second order is modeled through I/[A]/ linear.
The other method known as the proportionality method, determines the rate order of the reactants, by monitoring the change on the rate of the reaction as the initial incineration of the reactants are manipulated. Absorbency spectroscopy is used to monitor concentration as a function of time. Due the transparent nature of the bleach, absorption spectroscopy couldn’t be used to directly monitor its concentration. But knowing the ratio of the dilutions made, the concentration of the bleach could be indirectly measured.
The dilutions were made in even ratios in order to make the effect of concentration on rate more easily observable and measurable. Experimental: Materials: Cavetti, 150 ml beaker 100 ml beaker, graduated cylinder, cavetti, pectoral, Stock dye, bleach, The original stock solution of the dye and bleach were too concentrated and if used wouldn’t have being an effective use of time. A 1/100 dilution from stock solution of both the bleach and dye solutions produced solutions that would give just enough time for the data to be collected before reaction went to completion.
Using a graduated pipette 1 ml of 1. IEEE-3 M dye was transferred into a 150 ml beaker. A graduated cylinder was used to measure out 99 ml of water which was then mixed with the dye, to produce a 100 ml solution. The resulting solution, now 10% of the original concentration of the stock solution (1. IEEE-5 M). The procedures depicted above were then used to obtain a 8. 255 E-3 M of the bleach solution. After obtaining diluted solution, a graduated pipette was used to transfer ml of bleach and 3 ml of dye into different 10 ml beakers.
The spectrometer is used to monitor absorbency as a function of time. Knowing absorbency, beer’s law can be used to obtain concentration. To calibrate the spectrometer, ml of ODL water was pipette in a cavetti. Having calibrated the spectrometer, logger pro was switch to time eased mode and set to record absorbency every second for 500 seconds. The ml of bleach and 3 ml dye dilution were then mixed together to make a 1:1 solution. Having initiated the reaction, the 6 ml resulting solution was quickly transferred to the cavetti and logger pro used to collect the absorbency data.
The RE value, which depicts precision in the data, helped determine the model which best fit the data that was obtained. Based on the RE value of 0. 9996, higher than all the other models, concentration of dye as a function of time was best integrated in to Len model, indicating the reaction was 1st order. Because the concentration of the bleach couldn’t be directly measured as time progressed, the proportionality teeth was used to find order of the bleach, knowing its initial concentration and if the concentration of the dye was kept constant.
By manipulating the initial concentration of the bleach for two trials, , and 1:2 ratio of dye to bleach, its effect on the rate could be observed. Because the rate doubled when the concentration of bleach was double, the proportionality method indicated that the rate order with respect to the bleach was approximately first order. The rate order information was used in determining the rate constant which allowed for resulting rate law, rate=0. 408[dye]1[bleach]1. A lot of the data obtained in our experiment relied on approximation, which in its own respect changes the validity of our data.
For the integrated rate law model, the RE value was very close for all the models which created an uncertainty in the rate order of the dye. Although it may be attributed to experimental errors, the RE value for the concentration of dye vs.. Time model was higher than the RE value for the Len model, or inversely related model in the third trial. This created a change from the first two trials which both indicated that the Len model was more precise than the other two models. The proportionality used an average in rates to obtain the rate order.
The deviation between these rates was greater for some trials than it was for others and reduced the accuracy and therefore validity of the data. In the course of the experiment several assumptions were made which may have being contributing sources of errors. It was assumed that the temperature was kept constant throughout all the trials therefore the rate constant was unchanged for all of them. It was also assumed that when one reactant was kept constant and in excess, it didn’t have an overall effect on the order of the reaction.
The integrated rate law model failed to account for accuracy and instead shot for precision. It was geared at finding which the models best fit our data and restricted the range of accuracy by limiting it only to three models. Reaction order that were fraction or decimals wouldn’t have being accounted for in this case. Also in converting from absorbency to concentration, the values in the beers law model were assumed to be the same for previous experiments performed. Although this assumption may prove correct, if false it may have produced very misleading data.
Also the handling of the cavetti and making of the dilution were factors that may also have affected our data. One way of improving the certainty of our data was to perform more trials with different concentrations and different ratios. In the case of the integrated rate law model, the proportionality method could have being used to verify the data obtained. Also being certain about the values used in the beer’s law conversion may have improved certainty in our data. Because the bulk of our experiment relied on averages and estimations, the information obtained was very uncertain.