Some probem in my salters investigation

[i25959341]

i m doing the kinetic of iodine and propanone in acid condition using colorimeter and observing the absorbance and initially i don't think i will need a calibration curve becos absorbance is poprptional to concentration and i only need to look the shape of the graph to determine the order of the reaction, hence i plot an graph with absrobance against time and find the Initial rate for each concentrations of the reactnats and plot a graph wiht rates agasint concentration.


now the problem is i also want to know the activation energy and need to plot the arrhenius plot lnk =lna-lnE/PT.
now i want to save time, so i use the absorbance against time graph to find the initial rate of the reaction and use the rate law ,rate=k[r]^e[g]^f,(at this point of the experiment i expected that i kno the order of the reaction alreayd) and basiclly find k

and i just want to ask, since absorbance is proportional to concentration , thus will the tangent at time zero at absorbance against time graph be the initial rate value for my experiment or is it missing a constant??

secondly is my method of determining activation energy experiment sound correct??

 

[Nino MMP]

The tangent at time zero on the absorbance against time graph should not be used to calculate the initial rate of the reaction. You will need to use the rate equation (rate = k[reactant]^e[reactant]^f) and measure the concentration of each reactant to obtain the rate constant k. Once you have obtained the rate constants for different concentrations, you can plot an Arrhenius plot to determine the activation energy.

 

[Blueshift5]

It is great that you are conducting a kinetic investigation on the reaction between iodine and propanone in acid conditions. However, there are a few issues with your approach that need to be addressed.

Firstly, it is important to have a calibration curve for your colorimeter in order to accurately determine the concentration of your reactants. Absorbance may be proportional to concentration, but this relationship is not always linear and a calibration curve can help to correct for any non-linearity.

Secondly, while plotting the initial rates against concentration can give you an idea of the reaction order, it is not a reliable method. It is best to determine the reaction order using a method such as the method of initial rates or the method of integrated rate laws.

Regarding your question about the tangent at time zero on the absorbance versus time graph, this value may not necessarily be the initial rate as it depends on the sensitivity and accuracy of your colorimeter. It would be best to use a more reliable method to determine the initial rate.

As for your method of determining activation energy, it is important to have multiple data points at different temperatures in order to accurately plot the Arrhenius plot. Additionally, it is important to ensure that the reaction is taking place under pseudo-first order conditions for this method to be valid.

In conclusion, it is important to carefully plan and execute your experiment to ensure accurate and reliable results. It may be helpful to consult with a mentor or supervisor to discuss and refine your experimental approach. Good luck with your investigation!